December 11, 2023 • 33 mins
Guess what? Every time you power on or restart your computer, it runs a series of complex diagnostic processes that are critical for performance. That's right, your CPU isn't just twiddling its electronic thumbs; it's conducting Post Power On Self-Tests. We're pulling back the curtain on this hidden world, breaking down every crucial step from resetting operations to extensive memory tests. You'll gain a whole new appreciation for the work your CPU puts in before it even starts executing your commands.
But wait, there's more! Your computer isn't just checking itself - it's ensuring the stability of your entire system. We're talking power supply, IO devices, everything. We'll examine the safety nets in place, from overvoltage and undervoltage protection to short circuit protection, and how your power supply fan plays a crucial role. And what about those input-output devices we take for granted, like keyboards and storage devices? You'll learn how they're initialized, tested, and safeguarded to prevent damage to other components.
However, it's not all tech talk. I'm also inviting all you creators in the field of educational podcasting to be part of my doctoral thesis research. Your input is invaluable and will contribute significantly to this burgeoning field of research. Tune in, learn, and let’s push the boundaries of educational podcasting together. So, are you ready to join the conversation on Technology Tap? It's time to power up your knowledge!
If you want to help me with my research please e-mail me.
Professorjrod@gmail.com
If you want to join my question/answer zoom class e-mail me at
Professorjrod@gmail.com
Art By Sarah/Desmond
Music by Joakim Karud
Little chacha Productions
Juan Rodriguez can be reached at
TikTok @ProfessorJrod
ProfessorJRod@gmail.com
@Prof_JRod
Instagram ProfessorJRod
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:28):
And welcome to Technology Tap.
I'm Professor J Rod.
In this episode we're going totalk about Posts Power On
Self-Tests.
Let's get into it.
Alright, and welcome toTechnology Tap.
(01:08):
This is the first time that youare listening to me.
My name is Professor J Rod.
That's J-R-O-D, like thebaseball player set of A Rod.
It's J Rod and I am a Professorof Cyber at New York State
College and in this podcast whatwe do is that we talk about all
things com tier, talk about thetest with.
(01:31):
You know I'll do some topics oncom tier and you know just
about anything else that'sactually related to computers in
general.
But we mostly focus on the comtier series of exams, a plus
network plus, security plus,being the main ones.
Every now and then would dependto cloud plus CYSA plus, maybe
(01:53):
penetration testing that I'mplanning on taking soon.
So welcome to this the firsttime that you're listening to me
, and I appreciate it.
So let's take care of somehousekeeping first.
So, as you guys know, professorJ Rod wants to change to Dr J
Rod and I may need someassistance.
If any of you are educationalpodcasters like me, if you can
(02:19):
do me a favor, you can go to mywebsite, professor J Rodcom.
That's Professor J Rodcom, andthere will be a link for
educational podcast.
If you can, please do a surveyfor me.
I'm doing a survey oneducational podcasting, higher
(02:39):
education.
You know college really usingusing podcasting in higher
education, high school andcollege mainly.
So if you're a high schoolteacher or a professor like me
and you using podcasting toenhance your classroom, please,
please, please, fill out mysurvey.
(02:59):
I'm doing my doctoral thesis oneducational podcasting, so I
would really need yourassistance on that and, as
always, I appreciate each andevery one of my listeners.
All right, so let's get intotoday's topic post power on self
test.
What is power on self test?
Well, it's a diagnostic processthat a computer's essential
(03:23):
processing unit performs with acomputer is powered on or
restart.
The post is part of the systemsfirmware typically stored in
the computer's bios or the UEFI.
During post, the CPU and othercomponents are checked to ensure
they are functioning properly.
So I'm going to give you ageneral overview of what happens
(03:45):
during post and we're going tostart with the CPU.
The initialization of the CPUduring post involves preparing
the central processing unit foroperation.
This process ensures that theCPU starts in a known state and
is ready to execute instructions.
Here are the key steps involvedin initialization of CPU.
(04:06):
During post, one of the firstthings that it does is reset
operations.
When the computer's part on orrestarted, a reset signal is
sent to the CPU.
The CPU initializes itself byresetting its internal state to
a predefined starting point.
It also resets vectors the CPUfetches a reset vector.
(04:27):
A reset vector is a memoryaddress where the initial
program counter value is stored.
The program counter is aregister in the CPU that keeps
track of the memory address ofthe nest instructions to be
executed.
Setting program counter the CPUsets the program counter with
the value fetch from the resetvector.
This determines the startingpoint in memory for the
(04:49):
execution of instructions.
Initializations of registersthe CPU initializes its general
purpose registers to knownvalues.
Specific registers may be setto default values or cleared to
ensure a clean state.
Setting flags the CPU statusflags, such as zero flag, carry
flag and overflow flags, aretypically set to default values.
(05:14):
These flags are used toindicate the outcome or
algorithmic and logicaloperations.
Mode settings depending on theCPU architecture, the processor
may operate in different modes,for example real mode or
protected mode.
The CPU sets its mode to aninitial state determining how it
interacts with memory and othersystem components.
(05:39):
Self diagnostics and systemchecks.
The CPU may perform self testsand diagnostic checks during the
initialization to ensure theinternal components are
functioning correctly.
Any errors detected duringthese checks may result in error
messages or diagnostic codes.
By the end of the CPUinitialization process, the
(05:59):
processor is in a state where itcan't start executing
instructions from the systemfirmware or the boot loader.
The overall goal is toestablish a reliable and
consistent starting point forthe CPU's operation, ensuring
that subsequent instructions areexecuted correctly as part of
the boot up sequence.
Memory tests the post checks thesystem's RAM random access
(06:22):
memory to ensure that it'sfunctioning correctly.
This usually involves writingand reading data to and from
different memory locations.
The memory test is a crucialcomponent of the power on
self-test performed by thecomputer during the Buddha
process.
The purpose of the memory testis to check integrity of the
system's RAM and remember.
(06:43):
Ram is the volatile memory andthat stores data in machine code
currently being used andaccessed by the computer's
processor.
There is an overview of thememory test when it's typically
conducted during post.
Memory address check the poststarts by testing different
memory address to ensure thatthe RAM is accessible.
It writes specific patterns ofdata to different memory
(07:05):
locations and then reads thedata back to verify correctness.
Data bus test the data bus isthe communication pathway
between the CPU and the RAM.
The memory test checks the databus by writing data to the RAM
and then reading it back toensure that the data is
transferred correctly.
Address bus test the addressbus is responsible for
(07:27):
specifying a memory address.
The post tests the address busby verifying that the CPU can
correctly address differentlocations.
In RAM Pattern test.
The memory test often usesspecific patterns such as all
zeros or ones, or alternatingpatterns to write and read from
the memory.
This helps identify issues withspecific bits or cells.
(07:49):
In the memory Walking bit test,this test involves writing a
specific bit pattern to memoryand then shifting the bit
pattern to the next memorylocation.
It helps detect stuck or faultybits in memory Checkerboard
test.
The checkerboard testalternates between writing
patterns to odd and even memoryaddress.
(08:09):
It helps identify issues withadjacent memory locations.
March test March test involvesa sequence of read and write
operations that transfersthrough the memory Test.
Like March C and March B arevariations designed to detect
different types of memory faults.
Bit flip test Bit flip testintentionally flips individual
(08:34):
bits in memory to check if thememory can correctly store and
retrieve data.
Memory size detection the postmay also detect and verify the
amount of installed RAM toensure that the system
recognizes the correct memorystate.
If any errors are detectedduring the memory test, the post
typically generates errormessages or beep codes providing
(08:56):
information about the natureand location of the memory
issues.
Users or technicians can thenuse this information to diagnose
and address the hardwareproblems.
A successful memory test iscrucial for ensuring the
stability and reliability of thecomputer systems, as faulty RAM
can lead to a variety of issues, including system crashes, data
(09:19):
corruptions and unpredictablebehavior.
Next we're going to do powersupply checks.
Power supply checks areessential part of power on
subtests and the overall systemdiagnostics.
A stable and reliable powersupply is crucial for proper
functioning of a computer system.
(09:40):
Here are some common powersupply checks performed during
posts Voltage Rails Monitoringthe power supply provides
different voltage levels,commonly 12V, 5v, 3.3v to
various components on the system.
The post may check the voltageon these rails to ensure that
they are within acceptabletolerance levels.
(10:02):
Deviation from the specificvoltage level can indicate power
supply issues.
Power Good Signal the powersupply generates a power good
signal to indicate that allpower rails are stable and
within the specific voltagerange.
The system waits for the signalbefore proceeding with the boot
process.
The power good signal is notreceived, the system may halt to
(10:25):
prevent potential damage.
Overvoltage and undervoltageprotection the power supply may
have built in protectionmechanism to prevent overvoltage
or undervoltage situations.
The post checks for anyovervoltage or undervoltage
conditions and takes appropriateactions to safeguard the
(10:48):
components.
Short Circuit Protection Powersupply often short circuit
protection.
To prevent damage in the eventof a short circuit in the system
, the post may check for shortcircuits and respond accordingly
.
Power supply fan check the postmay check whether the fan and
the power supply is operational.
A malfunctioning fan can leadto overheating and the system
(11:13):
may halt or generate warnings ifthe fan is not working properly
.
Power on delay Some systemsincorporate a power on delay to
ensure that the property supplystabilizes before components are
operating.
This delay helps prevent issuesthat could arise from unstable
power supply during the initialmoments of powering.
(11:34):
On Load test the post mayperform load test to check how
well the power supply handlesfor any loads.
Fluctuation in power demands,such as during the startup of
components, should be handledsmoothly by the power supply
Power factor correction check.
Some power supplies include PFCor power factor correction to
(11:56):
improve the efficiency of powerusage.
The post may check whether thePFC is functioning properly.
If any issues are detectedduring the power supply checks,
the post may generate errormessages, beep codes or other
indicators to alert users ortechnicians about potential
problems.
Addressing power supply issuesis crucial to ensure the
(12:17):
system's stability and toprevent damage to other
components.
If you suspect power supplyproblems, it is recommended to
consult a system documentationor seek assistance from a
technician support or aqualified technician.
In other words, just throw itaway.
Do not try to fix a powersupply.
It is a $30 part that anycompany will have a spare.
(12:40):
Anything wrong with the powersupply.
Do not attempt to open it.
Just throw it out.
It is a $30 part.
Next we are going to doinitialization of input-opper
devices, which is a crucial stepin the post process.
Io devices include peripheralssuch as keyboards, mice, storage
devices and other externaldevices connected to the
(13:02):
computer.
The initialization of thesedevices ensure that they are
recognized and operational.
Here is an overview Enumeratingdevices the system's BIOS or
UEFI, begins by enumerating andidentifying the IO devices
connected to the system.
This process involvesidentifying the type and
(13:22):
location of each device.
Initializing system buses thesystem buses PCI, pcie that
connect to the CPU to various IOdevices are initialized.
This involves configuring thebus and ensuring proper
communication between the CPUand the connected devices.
Assigning resources the bus, orUEFI, assigns system resources,
(13:48):
such as IRQs, which areinterrupt requests, io addresses
and memory address to each IOdevice.
The allocations ensures thatdevices can operate without
conflicting with each other.
Testing IO devices the postperforms basic tests on each IO
device to ensure that they arefunctional.
For example, the system maycheck whether a keyboard and a
(14:11):
mouse respond to input or if astorage device can be accessed.
Loading device drivers thesystem firmware may load basic
device drivers for a central IOdevice, enabling communications
between the operating system andthese devices.
This is often from a linearitystep to ensure that the critical
devices can be accessed duringthe boot process.
(14:35):
When you turn it on, it's notloading right away to the
operating system.
It's doing posts and bios.
But what if you need to getinto the bios or the CMOS before
it goes to the operating system?
It has to load these drivers,minimal as they may be, in order
for you to see the screen.
To use the keyboard, forexample, uefi is the ability to
(15:02):
use the mouse and sometimesnetwork access.
Detecting bootable devices isnext.
The system identifies andprioritizes bootable devices
such as hard drives, solid statedrives and optical drives.
The bios, or UEFI, determinesthe device from which the
operating system will be loaded.
(15:23):
Initializing mass storagedevices Mass storage devices,
such as hard drive or SSD,undergo initialization checks to
ensure they are responsive andaccessible.
The system may check for thepresence of a valid boot records
on these devices.
Initializing display devicesDisplay devices such as graphic
(15:43):
cards and monitors areinitialized to enable video
output.
The system sets displayresolutions and refresh rates
based on the capabilities of theconnected monitor.
Loading expansion card firmwareIf there are expansion cards in
the system, for example graphiccards or network cards, their
firmware may be loaded andinitialized.
(16:05):
This ensures that additionalfunctionality provided by these
cards is available to the system.
Network initialization If thesystem has integrated or add-on
network interfaces, the firmwaremay initialize these interfaces
.
This enables networkcommunications and may involve
obtaining an IP address throughDHCP Dynamic Host Configuration
(16:29):
Protocol.
If any issues are detected dueto initialization of IO devices,
the posts may generate errors,beep codes or display
information to indicate thenature of the problem.
Proper initialization of the IOdevice is essential for the
successful booting of theoperating system and overall
functionality of the computersystem.
(16:52):
Bios integrity check is acritical step in post it
processes during the computer'sboot up sequence.
The BIOS is firmware thatresides on a chip on the
motherboard and provideslow-level control for the
hardware components of thecomputer.
Ensuring the integrity of BIOSis critical for the system
(17:15):
stability and proper functioning.
And let's do an overview First.
We're going to start with readonly memory check.
The BIOS is typically stored innon volatile memory chip, often
referred to as ROM, read onlymemory or flash memory.
During the post, the systemchecks the integrity of the BIOS
stored in RAM.
This involves reading the BIOScodes in the memory and
(17:38):
verifying its integrity Check.
Some verification the BIOS codeis often accomplished by
checksum or hash value, which isa mathematical sum calculated
based on the contents of theBIOS.
The post performs a checksumverification to ensure that the
calculated checksum matches theexpected value.
If the checksum does not match,it is suggested that BIOS code
(18:00):
may be corrupted or modified.
Digital signature check Somemodern systems may use digital
signature to verify theauthenticity and integrity of
BIOS code.
A digital signature is acryptographic mechanism that
ensures the code has not beentampered with.
The BIOS may contain a digitalsignature and the post checks is
(18:21):
validity.
Boot BIOS integrity check.
The BIOS typically has a smallportion known as boot block that
is responsible for essentialfunctions, including the initial
stages of the boot process.
The integrity of the boot blockis checked to ensure that
critical functions such asreading from storage devices are
(18:42):
intact.
Error handling If any issuesare detected during BIOS
integrity check, the post maygenerate error messages, beep
codes or display informationindicating a problem.
Error messages may providedetails about the nature of the
issue, such as checksum matchmass or corrupted BIOS.
Bios recovery, if is available.
(19:05):
Some systems are equipped withBIOS recovery mechanism that can
be activated if the primaryBIOS is found to be corrupt.
In the event of a BIOSintegrity failure, the system
may attempt to recover using abackup copy of BIOS or initiate
a process to reflash the BIOS.
Ensuring the integrity of theBIOS is critical because the
(19:27):
BIOS plays a fundamental role inthe early stages of the boot
process.
If the BIOS is compromised orcorrupted, it can lead to the
system's instability, failuresor the inability to boot the
operating system.
Manufacturers often providetools and procedures for
updating or recovering BIOS incase of issues, emphasizing the
(19:48):
importance of maintaining BIOSintegrity.
Expansion cards are part of thepost process that occurs during
the computer's boot-up sequence.
The post verifies the prints offunctionalities cards to ensure
they're proper.
Systems operation here is anoverview of expansion cards.
Checks Presence detection thepost checks for the presence of
(20:11):
expansion cards and theirrespective slots on the
motherboard.
It detects the type and thenumber of expansion cards
installed.
Initialization of integratedcircuits Each expansion card
contains integrated circuitsresponsible for specific
functions.
The post initializes these ICsto ensure they are ready for
(20:31):
operation.
Testing for basic functionalitythe post performs basic tests
to ensure that each expansioncard is functioning correctly.
For example, a graphic card maybe tested for video output, a
network card for networkconnectivity or a sound card for
audio output.
Address assignments the systemassigns address, interrupts and
(20:53):
other resources to eachexpansion card.
To prevent conflicts, the postensures that these assignments
are made correctly and do notover-light with other devices,
rrq or interrupt requesthandling Expansion cards often
use interrupts to communicatewith the CPU.
The post checks the RRQsettings for each expansion card
to prevent conflicts and ensureproper communication.
(21:16):
And you are so lucky nowadays,guys, that you do not have to
deal with RRQs.
Back in the day you had to.
And let me tell you somethingit was not pretty at all.
Very complicated, especiallywith modems and sound cards when
they first came out.
Expansion ROM initializationSome expansion cards have
(21:36):
built-in firmware or expansionROMs that provide additional
functionality.
The post initializes theexpansion ROMs to make sure they
are accessible and operational.
Error detecting and reportingIf any issues are detected
during expansion card checks,the post may generate error
messages, beep codes or displaydiagnostic information.
(21:57):
Error messages help identifythe specific expansion card
causing the problem.
Graphic card initialization theinitialization of a graphic
card is a crucial part of theexpansion card checks.
The post ensures that thegraphic card is operational and
capable of providing videooutput to the display.
(22:17):
Voodooable device identificationSome expansion cards, such as
storage controllers, may beresponsible for connecting to a
voodooable device, for examplehard drive.
The post identifies andverifies the presence of these
voodooable devices.
Network interfaceinitialization If a network card
is present, the postinitializes it to enable network
(22:39):
connectivity.
Like I said before, it alsoinvolves obtaining an IP address
through DHCP.
These expansion card checks areimportant for ensuring that all
components of the system areproperly detected and
initialized during the voodooprocess.
Any issues identified duringthis phase can be critical for
(22:59):
diagnostic and resolvinghardware related problems.
If there are problems withspecific expansion cards, user
may need to reset or replace thecard, update firmware or
drivers or address any conflictsin an expansion configuration.
Next we're going to talk aboutthe graphics card, because
that's very important.
The display test is a criticalcomponent.
(23:24):
A post during the computer'sboot up sequence to test focus
on verifying the functionalityof the display subset, which
includes the graphic card,monitor and related components.
The primary goal is to ensurethat the system can provide
video output to the display andthe display is capable of
presenting information for theuser.
Here's an overview.
(23:45):
Graphic card initialization thepost begins by initializing the
graphic card which isresponsible for rendering image
and showing them to the displayand sending them to the display.
This involves configuring thegraphic card and ensuring that
it's operational.
Checking video memory the postmay perform a quick test of the
video memory on the graphic cardto ensure that it's functioning
(24:07):
correctly.
Any issues with video memorycan lead to graphical artifacts
or display issues.
Setting display parameters thesystem configures display
parameters such as screenresolution and refresh rate,
based on the false settings oruser defined preference stored
in BIOS or UEFI.
Output to display.
(24:27):
The post sends a signal to thedisplay instructing it to show
specific patterns or information.
This allows the system toverify that the display is
receiving signals and presentinformation.
Color and pixel and pixel testthe display may show series of
colors, patterns or pixel gridsto ensure that each pixel on the
(24:48):
screen is functional.
This helps identify any deadpixels or abnormalities in the
display.
Testing multiple monitors isapplicable.
You're not doing that.
You're not living.
System with multiple monitorsmay undergo tests to ensure that
all connected devices arefunctioning as expected.
(25:10):
This includes checking forcorrected detection and
configuration of multipledisplay outputs.
User interface elements somesystems display basic user
interface elements during posts,such as the manufacturer's logo
, system information ordiagnostic messages.
This provides visual feedbackto the user and indicates that
(25:33):
the display subsystem isoperational.
Error messages on beep codes Ifany issues are detected during
the display test, the post maygenerate error messages, beep
codes or other visual indicatorsto alert the user.
These indicators help diagnoseproblems with graphic cards,
monitor or display connections.
(25:54):
External display checks Forsystems with external display
connectors HDMI or display portthe post may check the
functionality of theseconnectors and the corresponding
signals.
The display test is crucialbecause it confirms that the
computer can communicate withthe display hardware, providing
a visual interface for the user.
(26:15):
If the issues are identifiedduring the test, users may need
to check the display connectorstest with a different monitor or
different cable.
They could also troubleshootproblems with the graphic cards
or its drivers.
The visual feedback providedduring the display test is
valuable for diagnosing andresolving potential display
(26:35):
related issues.
Storage device checks have anintegral part of posts.
These checks are designed toverify the present integrity and
functionality of storagedevices such as hard drives,
solid state drives and otherstorage peripherals.
First, we're going to go overdetecting attached storage
devices.
The post begins by detectingand identifying the storage
(26:59):
devices connected to the system.
This includes internal drives,external drives and other
storage peripherals.
Initialization of storagecontrollers the storage
controllers can manage datatransfer between the storage
devices and the rest of thesystems.
Are initiated are initialized.
This involves checking theintegrity of the controller and
(27:20):
ensuring that it's ready tocommunicate with attached
storage devices.
Checking storage device powerand connection the post verifies
that the power supply and thedata connected to the storage
devices are stable and correctlyconfigured.
Loose cables or power issuescan lead to storage device
failures.
Smart Self-monitoring analysisand reporting checks If
(27:41):
supported by the storage device,the post may query smart data
to assess the health of thedrives.
Smart checks can identifypotential issues with the drives
, such as bad sectors orintimate drive failure.
So that you can back up BiosUEFI recognition the post
ensures that the system, bios orthe UEFI, recognizes the
(28:02):
storage device.
The bios UEFI providesinformation about the connected
drives and their basicconfigurations.
Boot sector and partitionchecks the post checks the boot
sector and the partitioninformation of bootable drives
to ensure they are correctlyconfigured.
If the system is configured toboot from a specific drive, the
(28:23):
post verifies that the drivecontains a valid boot loader.
Read and write tests Basic readand write tests may be performed
on the storage device to ensurethat the data can be properly
written to and read from thedevices.
These tests help identifyissues with data integrity and
storage device performance.
Raid configuration checks, ifapplicable.
(28:44):
In a system with a raid whichis redundant a raid of
independent disk configurationsthe post verifies the status and
integrity of the raid arrays.
This includes checking forfailed drives and ensuring that
the raid's configuration isconsistent.
Error handling If any issuesare detected during the storage
(29:04):
device checks, the post maygenerate errors beep codes or
display diagnostic information.
These indicators help identifythe nature of the storage
related problems, loadingstorage device drivers if needed
.
If specific storage devices arerequired for proper operations,
the post may load these driversto enable communications
(29:27):
between the operating system andthe storage device.
Ensuring the properfunctionality of the storage
device is critical for thesuccessful booting of the
operating system and overallsystem stability.
If storage devices areidentified during post, users
may need to check cables,replace faulty drives, update
firmware or addressconfiguration problems to ensure
(29:49):
reliable storage performance.
If issues are detected duringpost, the system may display
error messages.
Beep codes indicate the natureof the problem.
These codes can helptechnicians diagnosed and
troubleshoot hardware issues.
Now we know that if we haveissues with post right, there's
(30:13):
this thing called a postcard.
I honestly have never workedwith a postcard, but I'm under
the assumption that if you workfor a company like Dell and all
you're doing all day is fixingmotherboards, that you will be
familiar with postcards.
But postcards if, if you don'tget any beep codes right and and
(30:36):
anything that displays on themonitor right, you can use this
card and that card will give youan error number and then you
look up what that error numbermeans, kind of like when you you
know that when you take yourcar to the mechanic and they and
they, you know they, they runthat test for error codes.
Post does the same thing forPCs, so it pretty you know it
(30:58):
does the same thing as it as youwould for your car.
All right, that's gonna be itfor post again.
Ladies and gentlemen, if you area creator of educational
podcast, kind of like I am right, this is considered educational
podcast.
If you can go on my website,professor J rod that's J R O D
(31:24):
and you will see a tab on therethat would say for you know,
research survey, and then youclick on that and then you will
see the survey.
Please only click on it.
If you are an educationalpodcaster in higher education,
high school, in college, you'llbe doing me a great favor, as am
(31:44):
I doing my dictatorial research, my thesis on educational
podcast.
So I would appreciate if youguys can help me with that and,
as always, thank you.
All right, that's gonna be allfor today.
(32:05):
Thank you very much forlistening and this is professor
J rod signing off.
This have been production oflittle chacha.
(32:29):
Productions are by Sarah, musicby Jo Kim.
If you want to reach me, youcan email me at professor J rod,
that's J R O D at gmailcom.
I'm also on tiktok, professor Jrod, and on Instagram,
professor J rod.
And welcome to Technology Tap.
I'm Professor J Rod.
In this episode we're going totalk about Posts Power On
Self-Tests.
Let's get into it.
Alright, and welcome toTechnology Tap.
(01:08):
This is the first time that youare listening to me.
My name is Professor J Rod.
That's J-R-O-D, like thebaseball player set of A Rod.
It's J Rod and I am a Professorof Cyber at New York State
College and in this podcast whatwe do is that we talk about all
things com tier, talk about thetest with.
(01:31):
You know I'll do some topics oncom tier and you know just
about anything else that'sactually related to computers in
general.
But we mostly focus on the comtier series of exams, a plus
network plus, security plus,being the main ones.
Every now and then would dependto cloud plus CYSA plus, maybe
(01:53):
penetration testing that I'mplanning on taking soon.
So welcome to this the firsttime that you're listening to me
, and I appreciate it.
So let's take care of somehousekeeping first.
So, as you guys know, professorJ Rod wants to change to Dr J
Rod and I may need someassistance.
If any of you are educationalpodcasters like me, if you can
(02:19):
do me a favor, you can go to mywebsite, professor J Rodcom.
That's Professor J Rodcom, andthere will be a link for
educational podcast.
If you can, please do a surveyfor me.
I'm doing a survey oneducational podcasting, higher
(02:39):
education.
You know college really usingusing podcasting in higher
education, high school andcollege mainly.
So if you're a high schoolteacher or a professor like me
and you using podcasting toenhance your classroom, please,
please, please, fill out mysurvey.
(02:59):
I'm doing my doctoral thesis oneducational podcasting, so I
would really need yourassistance on that and, as
always, I appreciate each andevery one of my listeners.
All right, so let's get intotoday's topic post power on self
test.
What is power on self test?
Well, it's a diagnostic processthat a computer's essential
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processing unit performs with acomputer is powered on or
restart.
The post is part of the systemsfirmware typically stored in
the computer's bios or the UEFI.
During post, the CPU and othercomponents are checked to ensure
they are functioning properly.
So I'm going to give you ageneral overview of what happens
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during post and we're going tostart with the CPU.
The initialization of the CPUduring post involves preparing
the central processing unit foroperation.
This process ensures that theCPU starts in a known state and
is ready to execute instructions.
Here are the key steps involvedin initialization of CPU.
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During post, one of the firstthings that it does is reset
operations.
When the computer's part on orrestarted, a reset signal is
sent to the CPU.
The CPU initializes itself byresetting its internal state to
a predefined starting point.
It also resets vectors the CPUfetches a reset vector.
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A reset vector is a memoryaddress where the initial
program counter value is stored.
The program counter is aregister in the CPU that keeps
track of the memory address ofthe nest instructions to be
executed.
Setting program counter the CPUsets the program counter with
the value fetch from the resetvector.
This determines the startingpoint in memory for the
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execution of instructions.
Initializations of registersthe CPU initializes its general
purpose registers to knownvalues.
Specific registers may be setto default values or cleared to
ensure a clean state.
Setting flags the CPU statusflags, such as zero flag, carry
flag and overflow flags, aretypically set to default values.
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These flags are used toindicate the outcome or
algorithmic and logicaloperations.
Mode settings depending on theCPU architecture, the processor
may operate in different modes,for example real mode or
protected mode.
The CPU sets its mode to aninitial state determining how it
interacts with memory and othersystem components.
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Self diagnostics and systemchecks.
The CPU may perform self testsand diagnostic checks during the
initialization to ensure theinternal components are
functioning correctly.
Any errors detected duringthese checks may result in error
messages or diagnostic codes.
By the end of the CPUinitialization process, the
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processor is in a state where itcan't start executing
instructions from the systemfirmware or the boot loader.
The overall goal is toestablish a reliable and
consistent starting point forthe CPU's operation, ensuring
that subsequent instructions areexecuted correctly as part of
the boot up sequence.
Memory tests the post checks thesystem's RAM random access
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memory to ensure that it'sfunctioning correctly.
This usually involves writingand reading data to and from
different memory locations.
The memory test is a crucialcomponent of the power on
self-test performed by thecomputer during the Buddha
process.
The purpose of the memory testis to check integrity of the
system's RAM and remember.
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Ram is the volatile memory andthat stores data in machine code
currently being used andaccessed by the computer's
processor.
There is an overview of thememory test when it's typically
conducted during post.
Memory address check the poststarts by testing different
memory address to ensure thatthe RAM is accessible.
It writes specific patterns ofdata to different memory
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locations and then reads thedata back to verify correctness.
Data bus test the data bus isthe communication pathway
between the CPU and the RAM.
The memory test checks the databus by writing data to the RAM
and then reading it back toensure that the data is
transferred correctly.
Address bus test the addressbus is responsible for
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specifying a memory address.
The post tests the address busby verifying that the CPU can
correctly address differentlocations.
In RAM Pattern test.
The memory test often usesspecific patterns such as all
zeros or ones, or alternatingpatterns to write and read from
the memory.
This helps identify issues withspecific bits or cells.
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In the memory Walking bit test,this test involves writing a
specific bit pattern to memoryand then shifting the bit
pattern to the next memorylocation.
It helps detect stuck or faultybits in memory Checkerboard
test.
The checkerboard testalternates between writing
patterns to odd and even memoryaddress.
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It helps identify issues withadjacent memory locations.
March test March test involvesa sequence of read and write
operations that transfersthrough the memory Test.
Like March C and March B arevariations designed to detect
different types of memory faults.
Bit flip test Bit flip testintentionally flips individual
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bits in memory to check if thememory can correctly store and
retrieve data.
Memory size detection the postmay also detect and verify the
amount of installed RAM toensure that the system
recognizes the correct memorystate.
If any errors are detectedduring the memory test, the post
typically generates errormessages or beep codes providing
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information about the natureand location of the memory
issues.
Users or technicians can thenuse this information to diagnose
and address the hardwareproblems.
A successful memory test iscrucial for ensuring the
stability and reliability of thecomputer systems, as faulty RAM
can lead to a variety of issues, including system crashes, data
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corruptions and unpredictablebehavior.
Next we're going to do powersupply checks.
Power supply checks areessential part of power on
subtests and the overall systemdiagnostics.
A stable and reliable powersupply is crucial for proper
functioning of a computer system.
(09:40):
Here are some common powersupply checks performed during
posts Voltage Rails Monitoringthe power supply provides
different voltage levels,commonly 12V, 5v, 3.3v to
various components on the system.
The post may check the voltageon these rails to ensure that
they are within acceptabletolerance levels.
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Deviation from the specificvoltage level can indicate power
supply issues.
Power Good Signal the powersupply generates a power good
signal to indicate that allpower rails are stable and
within the specific voltagerange.
The system waits for the signalbefore proceeding with the boot
process.
The power good signal is notreceived, the system may halt to
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prevent potential damage.
Overvoltage and undervoltageprotection the power supply may
have built in protectionmechanism to prevent overvoltage
or undervoltage situations.
The post checks for anyovervoltage or undervoltage
conditions and takes appropriateactions to safeguard the
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components.
Short Circuit Protection Powersupply often short circuit
protection.
To prevent damage in the eventof a short circuit in the system
, the post may check for shortcircuits and respond accordingly
.
Power supply fan check the postmay check whether the fan and
the power supply is operational.
A malfunctioning fan can leadto overheating and the system
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may halt or generate warnings ifthe fan is not working properly
.
Power on delay Some systemsincorporate a power on delay to
ensure that the property supplystabilizes before components are
operating.
This delay helps prevent issuesthat could arise from unstable
power supply during the initialmoments of powering.
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On Load test the post mayperform load test to check how
well the power supply handlesfor any loads.
Fluctuation in power demands,such as during the startup of
components, should be handledsmoothly by the power supply
Power factor correction check.
Some power supplies include PFCor power factor correction to
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improve the efficiency of powerusage.
The post may check whether thePFC is functioning properly.
If any issues are detectedduring the power supply checks,
the post may generate errormessages, beep codes or other
indicators to alert users ortechnicians about potential
problems.
Addressing power supply issuesis crucial to ensure the
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system's stability and toprevent damage to other
components.
If you suspect power supplyproblems, it is recommended to
consult a system documentationor seek assistance from a
technician support or aqualified technician.
In other words, just throw itaway.
Do not try to fix a powersupply.
It is a $30 part that anycompany will have a spare.
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Anything wrong with the powersupply.
Do not attempt to open it.
Just throw it out.
It is a $30 part.
Next we are going to doinitialization of input-opper
devices, which is a crucial stepin the post process.
Io devices include peripheralssuch as keyboards, mice, storage
devices and other externaldevices connected to the
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computer.
The initialization of thesedevices ensure that they are
recognized and operational.
Here is an overview Enumeratingdevices the system's BIOS or
UEFI, begins by enumerating andidentifying the IO devices
connected to the system.
This process involvesidentifying the type and
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location of each device.
Initializing system buses thesystem buses PCI, pcie that
connect to the CPU to various IOdevices are initialized.
This involves configuring thebus and ensuring proper
communication between the CPUand the connected devices.
Assigning resources the bus, orUEFI, assigns system resources,
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such as IRQs, which areinterrupt requests, io addresses
and memory address to each IOdevice.
The allocations ensures thatdevices can operate without
conflicting with each other.
Testing IO devices the postperforms basic tests on each IO
device to ensure that they arefunctional.
For example, the system maycheck whether a keyboard and a
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mouse respond to input or if astorage device can be accessed.
Loading device drivers thesystem firmware may load basic
device drivers for a central IOdevice, enabling communications
between the operating system andthese devices.
This is often from a linearitystep to ensure that the critical
devices can be accessed duringthe boot process.
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When you turn it on, it's notloading right away to the
operating system.
It's doing posts and bios.
But what if you need to getinto the bios or the CMOS before
it goes to the operating system?
It has to load these drivers,minimal as they may be, in order
for you to see the screen.
To use the keyboard, forexample, uefi is the ability to
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use the mouse and sometimesnetwork access.
Detecting bootable devices isnext.
The system identifies andprioritizes bootable devices
such as hard drives, solid statedrives and optical drives.
The bios, or UEFI, determinesthe device from which the
operating system will be loaded.
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Initializing mass storagedevices Mass storage devices,
such as hard drive or SSD,undergo initialization checks to
ensure they are responsive andaccessible.
The system may check for thepresence of a valid boot records
on these devices.
Initializing display devicesDisplay devices such as graphic
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cards and monitors areinitialized to enable video
output.
The system sets displayresolutions and refresh rates
based on the capabilities of theconnected monitor.
Loading expansion card firmwareIf there are expansion cards in
the system, for example graphiccards or network cards, their
firmware may be loaded andinitialized.
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This ensures that additionalfunctionality provided by these
cards is available to the system.
Network initialization If thesystem has integrated or add-on
network interfaces, the firmwaremay initialize these interfaces
.
This enables networkcommunications and may involve
obtaining an IP address throughDHCP Dynamic Host Configuration
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Protocol.
If any issues are detected dueto initialization of IO devices,
the posts may generate errors,beep codes or display
information to indicate thenature of the problem.
Proper initialization of the IOdevice is essential for the
successful booting of theoperating system and overall
functionality of the computersystem.
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Bios integrity check is acritical step in post it
processes during the computer'sboot up sequence.
The BIOS is firmware thatresides on a chip on the
motherboard and provideslow-level control for the
hardware components of thecomputer.
Ensuring the integrity of BIOSis critical for the system
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stability and proper functioning.
And let's do an overview First.
We're going to start with readonly memory check.
The BIOS is typically stored innon volatile memory chip, often
referred to as ROM, read onlymemory or flash memory.
During the post, the systemchecks the integrity of the BIOS
stored in RAM.
This involves reading the BIOScodes in the memory and
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verifying its integrity Check.
Some verification the BIOS codeis often accomplished by
checksum or hash value, which isa mathematical sum calculated
based on the contents of theBIOS.
The post performs a checksumverification to ensure that the
calculated checksum matches theexpected value.
If the checksum does not match,it is suggested that BIOS code
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may be corrupted or modified.
Digital signature check Somemodern systems may use digital
signature to verify theauthenticity and integrity of
BIOS code.
A digital signature is acryptographic mechanism that
ensures the code has not beentampered with.
The BIOS may contain a digitalsignature and the post checks is
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validity.
Boot BIOS integrity check.
The BIOS typically has a smallportion known as boot block that
is responsible for essentialfunctions, including the initial
stages of the boot process.
The integrity of the boot blockis checked to ensure that
critical functions such asreading from storage devices are
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intact.
Error handling If any issuesare detected during BIOS
integrity check, the post maygenerate error messages, beep
codes or display informationindicating a problem.
Error messages may providedetails about the nature of the
issue, such as checksum matchmass or corrupted BIOS.
Bios recovery, if is available.
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Some systems are equipped withBIOS recovery mechanism that can
be activated if the primaryBIOS is found to be corrupt.
In the event of a BIOSintegrity failure, the system
may attempt to recover using abackup copy of BIOS or initiate
a process to reflash the BIOS.
Ensuring the integrity of theBIOS is critical because the
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BIOS plays a fundamental role inthe early stages of the boot
process.
If the BIOS is compromised orcorrupted, it can lead to the
system's instability, failuresor the inability to boot the
operating system.
Manufacturers often providetools and procedures for
updating or recovering BIOS incase of issues, emphasizing the
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importance of maintaining BIOSintegrity.
Expansion cards are part of thepost process that occurs during
the computer's boot-up sequence.
The post verifies the prints offunctionalities cards to ensure
they're proper.
Systems operation here is anoverview of expansion cards.
Checks Presence detection thepost checks for the presence of
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expansion cards and theirrespective slots on the
motherboard.
It detects the type and thenumber of expansion cards
installed.
Initialization of integratedcircuits Each expansion card
contains integrated circuitsresponsible for specific
functions.
The post initializes these ICsto ensure they are ready for
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operation.
Testing for basic functionalitythe post performs basic tests
to ensure that each expansioncard is functioning correctly.
For example, a graphic card maybe tested for video output, a
network card for networkconnectivity or a sound card for
audio output.
Address assignments the systemassigns address, interrupts and
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other resources to eachexpansion card.
To prevent conflicts, the postensures that these assignments
are made correctly and do notover-light with other devices,
rrq or interrupt requesthandling Expansion cards often
use interrupts to communicatewith the CPU.
The post checks the RRQsettings for each expansion card
to prevent conflicts and ensureproper communication.
(21:16):
And you are so lucky nowadays,guys, that you do not have to
deal with RRQs.
Back in the day you had to.
And let me tell you somethingit was not pretty at all.
Very complicated, especiallywith modems and sound cards when
they first came out.
Expansion ROM initializationSome expansion cards have
(21:36):
built-in firmware or expansionROMs that provide additional
functionality.
The post initializes theexpansion ROMs to make sure they
are accessible and operational.
Error detecting and reportingIf any issues are detected
during expansion card checks,the post may generate error
messages, beep codes or displaydiagnostic information.
(21:57):
Error messages help identifythe specific expansion card
causing the problem.
Graphic card initialization theinitialization of a graphic
card is a crucial part of theexpansion card checks.
The post ensures that thegraphic card is operational and
capable of providing videooutput to the display.
(22:17):
Voodooable device identificationSome expansion cards, such as
storage controllers, may beresponsible for connecting to a
voodooable device, for examplehard drive.
The post identifies andverifies the presence of these
voodooable devices.
Network interfaceinitialization If a network card
is present, the postinitializes it to enable network
(22:39):
connectivity.
Like I said before, it alsoinvolves obtaining an IP address
through DHCP.
These expansion card checks areimportant for ensuring that all
components of the system areproperly detected and
initialized during the voodooprocess.
Any issues identified duringthis phase can be critical for
(22:59):
diagnostic and resolvinghardware related problems.
If there are problems withspecific expansion cards, user
may need to reset or replace thecard, update firmware or
drivers or address any conflictsin an expansion configuration.
Next we're going to talk aboutthe graphics card, because
that's very important.
The display test is a criticalcomponent.
(23:24):
A post during the computer'sboot up sequence to test focus
on verifying the functionalityof the display subset, which
includes the graphic card,monitor and related components.
The primary goal is to ensurethat the system can provide
video output to the display andthe display is capable of
presenting information for theuser.
Here's an overview.
(23:45):
Graphic card initialization thepost begins by initializing the
graphic card which isresponsible for rendering image
and showing them to the displayand sending them to the display.
This involves configuring thegraphic card and ensuring that
it's operational.
Checking video memory the postmay perform a quick test of the
video memory on the graphic cardto ensure that it's functioning
(24:07):
correctly.
Any issues with video memorycan lead to graphical artifacts
or display issues.
Setting display parameters thesystem configures display
parameters such as screenresolution and refresh rate,
based on the false settings oruser defined preference stored
in BIOS or UEFI.
Output to display.
(24:27):
The post sends a signal to thedisplay instructing it to show
specific patterns or information.
This allows the system toverify that the display is
receiving signals and presentinformation.
Color and pixel and pixel testthe display may show series of
colors, patterns or pixel gridsto ensure that each pixel on the
(24:48):
screen is functional.
This helps identify any deadpixels or abnormalities in the
display.
Testing multiple monitors isapplicable.
You're not doing that.
You're not living.
System with multiple monitorsmay undergo tests to ensure that
all connected devices arefunctioning as expected.
(25:10):
This includes checking forcorrected detection and
configuration of multipledisplay outputs.
User interface elements somesystems display basic user
interface elements during posts,such as the manufacturer's logo
, system information ordiagnostic messages.
This provides visual feedbackto the user and indicates that
(25:33):
the display subsystem isoperational.
Error messages on beep codes Ifany issues are detected during
the display test, the post maygenerate error messages, beep
codes or other visual indicatorsto alert the user.
These indicators help diagnoseproblems with graphic cards,
monitor or display connections.
(25:54):
External display checks Forsystems with external display
connectors HDMI or display portthe post may check the
functionality of theseconnectors and the corresponding
signals.
The display test is crucialbecause it confirms that the
computer can communicate withthe display hardware, providing
a visual interface for the user.
(26:15):
If the issues are identifiedduring the test, users may need
to check the display connectorstest with a different monitor or
different cable.
They could also troubleshootproblems with the graphic cards
or its drivers.
The visual feedback providedduring the display test is
valuable for diagnosing andresolving potential display
(26:35):
related issues.
Storage device checks have anintegral part of posts.
These checks are designed toverify the present integrity and
functionality of storagedevices such as hard drives,
solid state drives and otherstorage peripherals.
First, we're going to go overdetecting attached storage
devices.
The post begins by detectingand identifying the storage
(26:59):
devices connected to the system.
This includes internal drives,external drives and other
storage peripherals.
Initialization of storagecontrollers the storage
controllers can manage datatransfer between the storage
devices and the rest of thesystems.
Are initiated are initialized.
This involves checking theintegrity of the controller and
(27:20):
ensuring that it's ready tocommunicate with attached
storage devices.
Checking storage device powerand connection the post verifies
that the power supply and thedata connected to the storage
devices are stable and correctlyconfigured.
Loose cables or power issuescan lead to storage device
failures.
Smart Self-monitoring analysisand reporting checks If
(27:41):
supported by the storage device,the post may query smart data
to assess the health of thedrives.
Smart checks can identifypotential issues with the drives
, such as bad sectors orintimate drive failure.
So that you can back up BiosUEFI recognition the post
ensures that the system, bios orthe UEFI, recognizes the
(28:02):
storage device.
The bios UEFI providesinformation about the connected
drives and their basicconfigurations.
Boot sector and partitionchecks the post checks the boot
sector and the partitioninformation of bootable drives
to ensure they are correctlyconfigured.
If the system is configured toboot from a specific drive, the
(28:23):
post verifies that the drivecontains a valid boot loader.
Read and write tests Basic readand write tests may be performed
on the storage device to ensurethat the data can be properly
written to and read from thedevices.
These tests help identifyissues with data integrity and
storage device performance.
Raid configuration checks, ifapplicable.
(28:44):
In a system with a raid whichis redundant a raid of
independent disk configurationsthe post verifies the status and
integrity of the raid arrays.
This includes checking forfailed drives and ensuring that
the raid's configuration isconsistent.
Error handling If any issuesare detected during the storage
(29:04):
device checks, the post maygenerate errors beep codes or
display diagnostic information.
These indicators help identifythe nature of the storage
related problems, loadingstorage device drivers if needed
.
If specific storage devices arerequired for proper operations,
the post may load these driversto enable communications
(29:27):
between the operating system andthe storage device.
Ensuring the properfunctionality of the storage
device is critical for thesuccessful booting of the
operating system and overallsystem stability.
If storage devices areidentified during post, users
may need to check cables,replace faulty drives, update
firmware or addressconfiguration problems to ensure
(29:49):
reliable storage performance.
If issues are detected duringpost, the system may display
error messages.
Beep codes indicate the natureof the problem.
These codes can helptechnicians diagnosed and
troubleshoot hardware issues.
Now we know that if we haveissues with post right, there's
(30:13):
this thing called a postcard.
I honestly have never workedwith a postcard, but I'm under
the assumption that if you workfor a company like Dell and all
you're doing all day is fixingmotherboards, that you will be
familiar with postcards.
But postcards if, if you don'tget any beep codes right and and
(30:36):
anything that displays on themonitor right, you can use this
card and that card will give youan error number and then you
look up what that error numbermeans, kind of like when you you
know that when you take yourcar to the mechanic and they and
they, you know they, they runthat test for error codes.
Post does the same thing forPCs, so it pretty you know it
(30:58):
does the same thing as it as youwould for your car.
All right, that's gonna be itfor post again.
Ladies and gentlemen, if you area creator of educational
podcast, kind of like I am right, this is considered educational
podcast.
If you can go on my website,professor J rod that's J R O D
(31:24):
and you will see a tab on therethat would say for you know,
research survey, and then youclick on that and then you will
see the survey.
Please only click on it.
If you are an educationalpodcaster in higher education,
high school, in college, you'llbe doing me a great favor, as am
(31:44):
I doing my dictatorial research, my thesis on educational
podcast.
So I would appreciate if youguys can help me with that and,
as always, thank you.
All right, that's gonna be allfor today.
(32:05):
Thank you very much forlistening and this is professor
J rod signing off.
This have been production oflittle chacha.
(32:29):
Productions are by Sarah, musicby Jo Kim.
If you want to reach me, youcan email me at professor J rod,
that's J R O D at gmailcom.
I'm also on tiktok, professor Jrod, and on Instagram,
professor J rod.
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