POST Troubleshooting Guide

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I know <html>, do you?
Seems like people are having this problem a lot so this is 4 people with POST issues, hope it helps ;)

POST Troubleshooting Steps

*(Power On Self Test)*


Each time the computer boots up the computer must past the POST. Below is the common procedure of the POST:

1. The first step of POST is the testing of the Power Supply to ensure that it is turned on and that it releases its reset signal.
2. CPU must exit the reset status mode and thereafter be able to execute instructions.
3. BIOS must be readable.
4. BIOS checksum must be valid, meaning that it must be readable.
5. CMOS be accessible for reading.
6. CMOS checksum must be valid, meaning that it must be readable.
7. CPU must be able to read all forms of memory such as the memory controller, memory bus, and memory module.
8. The first 64KB of memory must be operational and have the capability to be read and written to and from, and capable of containing the POST code.
9. I/O bus / controller must be accessible.
10. I/O bus must be able to write / read from the video subsystem and be able to read all video RAM..

If the computer does not pass any of the above tests, your computer will receive an irregular POST. An irregular POST is a beep code which is different from the standard, which can be either no beeps at all or a combination of different beeps indicating what is causing the computer not to past the POST.

Additional information: (READ THIS FIRST)

**This document is intended to help users who are experiencing issues with the POST and may have any of the below symptoms.I am not responible for any damage made from someone attempting to solve the issue**


1. Computer beeps irregularly when the computer is turned on.
2. Computer turns on but does not boot.

Note: Not all computers have beep codes, some of the newer computers have LED's that light up that indicate the error or have a sound file to indicate the error.

To diagnose the POST issue read **Section 1**

If your a getting a beep code sequence such as one long beep and two short beeps you may want to first look at **Section 1.1**

If you reboot the computer several times and it sometimes starts up you may want to first review **Section 1.2**

Make sure your computer is turning on, if you press the power button and nothing happens (no lights, no sound, no fans, etc.) then this issue is not a NO POST but is an power related issue see **Section 1.3**

~Section 1~


This issue can be caused by any of the below situations.

1. New hardware conflicting with old hardware
2. Bad or failing hardware device.
3. Other hardware issue.


Warning: Some of the below steps recommend removing physical parts within the computer. While in the computer it is highly recommend that you be aware of ESD and its potential hazards. *****Ground yourself before getting started*****

1. If any new hardware has been recently added to the computer, remove that hardware to make sure it is not the cause of your issue. If after removing the new hardware your computer works it's likely the computer is either not compatible with the new hardware or a system setting needs to be changed to work with the new hardware device.
2. Remove everything from the back of the computer except the power cable. Turn on the computer and see if it beeps normally. If the computer has never beeped also connect a monitor to the computer to see if any change occurs.
3. If you are receiving a sequence of beeps see our beep code page for a listing of different beep codes and their explanation and/or your motherboard or computer documentation. These beep codes are meant as a method of quickly identifying what computer component is failing or bad.
4. Make sure all fans are running in the computer. If a fan has failed (especially the heat sink fan for the CPU) your computer could be overheating and/or detecting the fan failure causing the computer not to boot.
5. If you were unable to determine by the beep code what is failing or do not have a beep code disconnect the IDE cables from the CD-ROM, Hard Drive, and Floppy drive from the Motherboard. If this resolves your irregular post attempt to connect each device one at a time to determine which device and or cable is causing the issue.
6. If the above recommendations still have not resolved the irregular POST attempt to disconnect the Riser board (if applicable) and/or each of the expansion cards. If this resolves the issue or allows the computer to post connect one card at a time until you determine which card is causing the issue.
7. If you continue to to receive the same problem with all the above hardware removed attempt to disconnect the CPU and RAM from the Motherboard. Once done insert the CPU and RAM back into the computer to see doing this resolves your issue.
8. If after doing all of the above recommendations you continue to have the same issues unfortunately it is likely that you have bad Motherboard, CPU, and or RAM. The next step would be either to replace these components and/or have the computer serviced. If you plan on doing the repairs yourself or you are a repair shop it is suggested that you replace the Motherboard first, RAM, and then the CPU in that order and/or try swappable parts.

~Section 1.1~


Below are the AMI BIOS Beep codes that can occur. However, because of the wide variety of different computer manufacturers with this BIOS, the beep codes may vary.

Beep Code Descriptions
1 short DRAM refresh failure
2 short Parity circuit failure
3 short Base 64K RAM failure
4 short System timer failure
5 short Process failure
6 short Keyboard controller Gate A20 error
7 short Virtual mode exception error
8 short Display memory Read/Write test failure
9 short ROM BIOS checksum failure
10 short CMOS shutdown Read/Write error
11 short Cache Memory error
1 long, 3 short Conventional/Extended memory failure
1 long, 8 short Display/Retrace test failed


Below are Award BIOS Beep codes that can occur. However, because of the wide variety of different computer manufacturers with this BIOS, the beep codes may vary.
Beep Code Description

1long, 2short- <Video adapter error> Either video adapter is bad or is not seated properly. Also, check to ensure the monitor cable is connected properly.
2 short beeps- <Non-Fatal Error> (reseat RAM, check other components)
Repeating (endless loop)- <Memory error> Check for improperly seated or missing memory.
1long, 3short- <No video card or bad video RAM> Reseat or replace the video card.
High frequency beeeps while running- <Overheated CPU> Check the CPU fan for proper operation. Check the case for proper air flow.
Repeating High/Low beeps- <CPU> Either the CPU is not seated properly or the CPU is damaged. May also be due to excess heat. Check the CPU fan or BIOS settings for proper fan speed.
Any other beep(s)- <RAM problem>

If any other correctable hardware issues, the BIOS will display a message.


Below are IBM BIOS Beep codes that can occur. However, because of the wide variety of models shipping with this BIOS, the beep codes may vary.
Beep Code Description

No Beeps No Power, Loose Card, or Short.
1Short Beep Normal POST computer is ok.
2Short Beep POST error review screen for error code.
Continuous Beep No Power, Loose Card, or Short.
Repeating Short Beep No Power, Loose Card, or Short.
1Long and 1Short Beep Motherboard issue.
1Long and 2Short Beeps Video (Mono/CGA Display Circuitry) issue.
1Long and 3Short Beeps Video (EGA) Display Circuitry.
3Long Beeps Keyboard / Keyboard card error.
1Beep Blank or Incorrect Display Video Display Circuitry.



Error Tone. (two sets of different tones) Problem with logic board or SCSI bus.
Startup tone, drive spins, no video Problem with video controller.
Powers on, no tone. Logic board problem.
High Tone, four higher tones. Problem with SIMM.


Below are the beep codes for PHOENIX BIOS Q3.07 OR 4.X
Beep Code Description / What to Check

1-1-1-3 Verify Real Mode.
1-1-2-1 Get CPU type.
1-1-2-3 Initialize system hardware.
1-1-3-1 Initialize chipset registers with initial POST values.
1-1-3-2 Set in POST flag.
1-1-3-3 Initialize CPU registers.
1-1-4-1 Initialize cache to initial POST values.
1-1-4-3 Initialize I/O.
1-2-1-1 Initialize Power Management.
1-2-1-2 Load alternate registers with initial POST values.
1-2-1-3 Jump to UserPatch0.
1-2-2-1 Initialize keyboard controller.
1-2-2-3 BIOS ROM checksum.
1-2-3-1 8254 timer initialization.
1-2-3-3 8237 DMA controller initialization.
1-2-4-1 Reset Programmable Interrupt Controller.
1-3-1-1 Test DRAM refresh.
1-3-1-3 Test 8742 Keyboard Controller.
1-3-2-1 Set ES segment to register to 4 GB.
1-3-3-1 28 Autosize DRAM.
1-3-3-3 Clear 512K base RAM.
1-3-4-1 Test 512 base address lines.
1-3-4-3 Test 512K base memory.
1-4-1-3 Test CPU bus-clock frequency.
1-4-2-4 Reinitialize the chipset.
1-4-3-1 Shadow system BIOS ROM.
1-4-3-2 Reinitialize the cache.
1-4-3-3 Autosize cache.
1-4-4-1 Configure advanced chipset registers.
1-4-4-2 Load alternate registers with CMOS values.
2-1-1-1 Set Initial CPU speed.
2-1-1-3 Initialize interrupt vectors.
2-1-2-1 Initialize BIOS interrupts.


I know <html>, do you?
2-1-2-3 Check ROM copyright notice.
2-1-2-4 Initialize manager for PCI Options ROMs.
2-1-3-1 Check video configuration against CMOS.
2-1-3-2 Initialize PCI bus and devices.
2-1-3-3 Initialize all video adapters in system.
2-1-4-1 Shadow video BIOS ROM.
2-1-4-3 Display copyright notice.
2-2-1-1 Display CPU type and speed.
2-2-1-3 Test keyboard.
2-2-2-1 Set key click if enabled.
2-2-2-3 56 Enable keyboard.
2-2-3-1 Test for unexpected interrupts.
2-2-3-3 Display prompt "Press F2 to enter SETUP".
2-2-4-1 Test RAM between 512 and 640k.
2-3-1-1 Test expanded memory.
2-3-1-3 Test extended memory address lines.
2-3-2-1 Jump to UserPatch1.
2-3-2-3 Configure advanced cache registers.
2-3-3-1 Enable external and CPU caches.
2-3-3-3 Display external cache size.
2-3-4-1 Display shadow message.
2-3-4-3 Display non-disposable segments.
2-4-1-1 Display error messages.
2-4-1-3 Check for configuration errors.
2-4-2-1 Test real-time clock.
2-4-2-3 Check for keyboard errors
2-4-4-1 Set up hardware interrupts vectors.
2-4-4-3 Test coprocessor if present.
3-1-1-1 Disable onboard I/O ports.
3-1-1-3 Detect and install external RS232 ports.
3-1-2-1 Detect and install external parallel ports.
3-1-2-3 Re-initialize onboard I/O ports.
3-1-3-1 Initialize BIOS Data Area.
3-1-3-3 Initialize Extended BIOS Data Area.
3-1-4-1 Initialize floppy controller.
3-2-1-1 Initialize hard-disk controller.
3-2-1-2 Initialize local-bus hard-disk controller.
3-2-1-3 Jump to UserPatch2.
3-2-2-1 Disable A20 address line.
3-2-2-3 Clear huge ES segment register.
3-2-3-1 Search for option ROMs.
3-2-3-3 Shadow option ROMs.
3-2-4-1 Set up Power Management.
3-2-4-3 Enable hardware interrupts.
3-3-1-1 Set time of day.
3-3-1-3 Check key lock.
3-3-3-1 Erase F2 prompt.
3-3-3-3 Scan for F2 key stroke.
3-3-4-1 Enter SETUP.
3-3-4-3 Clear in-POST flag.
3-4-1-1 Check for errors
3-4-1-3 POST done--prepare to boot operating system.
3-4-2-1 One beep.
3-4-2-3 Check password (optional).
3-4-3-1 Clear global descriptor table.
3-4-4-1 Clear parity checkers.
3-4-4-3 Clear screen (optional).
3-4-4-4 Check virus and backup reminders.
4-1-1-1 Try to boot with INT 19.
4-2-1-1 Interrupt handler error.
4-2-1-3 Unknown interrupt error.
4-2-2-1 Pending interrupt error.
4-2-2-3 Initialize option ROM error.
4-2-3-1 Shutdown error.
4-2-3-3 Extended Block Move.
4-2-4-1 Shutdown 10 error.
4-3-1-3 Initialize the chipset.
4-3-1-4 Initialize refresh counter.
4-3-2-1 Check for Forced Flash.
4-3-2-2 Check HW status of ROM.
4-3-2-3 BIOS ROM is OK.
4-3-2-4 Do a complete RAM test.
4-3-3-1 Do OEM initialization.
4-3-3-2 Initialize interrupt controller.
4-3-3-3 Read in bootstrap code.
4-3-3-4 Initialize all vectors.
4-3-4-1 Boot the Flash program.
4-3-4-2 Initialize the boot device.
4-3-4-3 Boot code was read OK.

~Section 1.2~


My computer does not start unless I restart it multiple times.


If a computer is able to successfully startup if it is restarted several times, it is likely that the computer is encountering one of the below issues.

1. Bad power supply or inadequate power supply
2. Bad hard disk drive
3. Other hardware issue


1.Bad power supply or inadequate power supply

-A bad, failing, or inadequate power supply is often the cause of this issue. If the hard disk drive is not getting enough power during the first time the computer starts, it will be unable to spin the hard disk platters fast enough to start the computer. However, if you restart the computer two, three, or more times, because the platters are already spinning, it is able to get the drive up to speed and able to boot off the drive.

-If you're encountering this issue after installing new hardware in the computer, it's also possible the power supply in the computer is not supplying adequate power to the computer. For most computers we recommend you have at the least a 300-watt power supply.

-Our first recommendation is to replace or replace and upgrade the power supply in the computer.

Bad hard disk drive

-This issue can also be caused by a failing or bad hard disk drive. Similar to the above issue, if there is a failure within the hard disk drive that is causing the disk platters to not spin up fast enough during the initial power up, you may also encounter this issue.

-If after replacing the power supply you continue to experience the same issue, it's likely that the hard disk drive is at fault and we suggest the hard disk drive be replaced.

Other hardware issue

-Although not as likely as the above two causes (bad power supply or hard drive), other hardware can potentially cause this issue to occur. Below are some other possibilities that may cause this issue.


-Replace the IDE/EIDE interface cable connected from the motherboard to the hard disk drive. If the cable is defective it could cause various issues with your hard disk drive.


-Finally, if the computer continues to exhibit the same issue after following all of the above steps, it's likely that the motherboard is defective and that it should be replaced.


~Section 1.3~


No power or computer does not turn on.

No power from the computer can be caused by any of the below possibilities.


1. Connections not connected properly.
2. Third-party hardware.
3. Bad power cable.
4. Incorrect power supply.
5. Bad battery.
6. Bad power supply, power button, and/or power board or inverter.


If you are uncertain if the computer is turning on or not, this can be easily checked by locating any fans in the computer or visible from the outside of the computer. If these fans are spinning, the computer is receiving power and this document may not apply to your issue.

Connections not connected properly

-Verify that the power connection is connected properly to the wall and the back of the computer. If the connections appear to be connected properly, attempt to disconnect and reconnection both ends of the cable.

-If you have a power strip (surge protector) or switch used to turn everything on at once, temporarily disconnect the computer from that switch and connect that cable directly to the wall. This will help verify that the strip or switch is not bad.

-Verify that the outlet works by connecting a different component to that switch.

Third-party hardware

-If additional hardware has been recently added to the computer it is recommend that you temporarily disconnect that device or devices from the computer to verify they are not preventing your computer from turning on.

Bad Power cable

-Verify that the cable supplying your computer is not bad or damaged by using another power cable. If you have a standard CRT monitor, this cable can be used in place of the computer power cable.

-If you have a portable computer or laptop, when the cables are plugged into the laptop you should see a power light or battery charge light. If this light is seen, this is a good indication that the power cable is good.

Incorrect power supply

-If you are building your own computer or if the computer has never turned on since you purchased it, it is possible you are using a power supply that does not supply enough power and/or the incorrect type of power supply. Verify your power supply meets the requirements of your motherboard and processor.

Bad battery

If your computer is a laptop or portable computer that utilizes a battery for mobility it is possible that the battery may be causing your issue.

* If your computer powers on when the cable is connected to the portable computer but not when it is disconnected, we recommend you purchase a new battery.
* If your computer does not power on when the battery is connected and when the power cable / charger cable is connected, try removing the battery and seeing if the computer can power on with only the power cable connected. If no power is still received, skip to the final section.

Bad Power Supply, power button, and/or power board or inverter

If, after following the above sections, your computer still receives no power, it is likely that a hardware component in the computer has failed. It is most likely that the power supply has failed. If you do not plan on replacing the power supply yourself or if you have a portable computer, we recommend having the computer serviced by your computer manufacturer or a local computer repair shop.

If you have a desktop computer and plan on trying to repair the computer yourself, we recommend you replace the components in your computer in the below order.

1. First open the computer and verify the power connections. You may also wish to consider disconnecting the main power cable and reconnecting the power cable to make sure it has not become loose. Also verify the power button cable is correctly connected to the Motherboard.
2. Replace the power supply with a new power supply.
3. Replace the motherboard.

Written by: Computer Hope's free computer help
Organized by : Sylwester. S
A.K.A Sylwek


Everything to Nothing
i know this is an old thread n im necroposting a bit but that'll come in usefull


I know <html>, do you?
Thanks for appreciating it , lots of people usually have problems with Posting when it come to computers , so i thought of rewriting it to help out others in fixing this issue

BTW i updated it so others came read it more clearly


Mod Emeritus
This is a great guide, sylwek. It should probably be stickied. I can make that happen, but I should also ask the higher ups, first.

Unfortunately though, not many come here, or even read any of the stickies...


I know <html>, do you?
It wouldnt be fair for others that have their stickies in the tutorial and mine on the Forum list , If people can find it then they're in luck

thnx anyway
and yes its already in the tutorial . My old one was deleted and this one was resticked as its updated


Solid State Member
Ive been looking for this stuff , learn alot ,many thanks どもありがとう。
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