CMOS shutdown Read/Write error
How to replace the CMOS battery
Issue
How to replace the CMOS battery.
Cause
Like any battery the computer CMOS battery can fail or lose its charge.
Solution
If your computer is losing its time or date settings, or you are receiving a message CMOS Read Error, CMOS checksum error, or CMOS Battery Failure, first try leaving the computer on for 24-hours. In some cases this can charge the battery and resolve your issue. This often resolves CMOS battery related issues when a computer has been left off for several months. If this does not resolve your issue follow the below steps.
Locate your CMOS battery
Caution: When inside your computer make sure you're aware of ESD and all it's potential dangers.
Open the computer case and find the battery on the computermotherboard, verify that it will be accessible and that it can be removed. Most computers today use a coin cell CMOS battery as shown in the image to the right.
If you are unable to locate your CMOS battery refer to your motherboard or computer documentation or contact your computer manufacturer for additional assistance in locating it.
Obtain battery information
Unfortunately, most manufacturers will not list the exact type and model of your CMOS battery; therefore, once you have located the battery, write down all information about the battery (Voltage, chemistry, wiring, and packaging). If possible, remove the battery and take it to the location you plan on purchasing a new battery from. The part number for this battery for most computers is CR2032.
Additional buying information can be found on our battery buying tips page.
Removing the battery
Caution: When inside your computer make sure you're aware of ESD and all it's potential dangers.
If you're computer is using a coin cell battery similar to the above example picture. Removing the battery is relatively simple. use your fingers to grab on the edge of the battery and pull it up and out of the container holding it. Some motherboards have a clip holding the battery down. If your computer has this clip you may need to use one had to move the clip up and the other hand to pull the battery out.
Unfortunately, not all CMOS batteries are removable; some manufactures will only allow a replacement battery to be added. If you're not using a coin cell battery and are not able to determine how to remove it refer to your motherboard or computer documentation or contact yourcomputer manufacturer for additional assistance in removing the battery or how to insert a new replacement battery.
Users with computers that do not have removable batteries only options to install a new battery will most likely also need to set a jumper when adding the new battery into their computer.
Insert the new battery
Once you have purchased a new battery, remove the old battery (as instructed above) and replace it with the new battery.
Enter CMOS values
Once the battery is replaced turn on the computer and resetting the CMOS values to the defaults. After the values have all been entered make sure to save the settings before exiting. Many CMOS setups allow you to press a key (such as F10) to save values and exit all in one action.
If after following all the above steps you continue to experience the same error when your computer starts or your computer is still unable to keep the stored values it's likely that you're experiencing a more serious issues. Most likely causes are bad power supply or bad motherboard.
Keyboard controller Gate A20 error
A20 error
Issue
A20 error.
Cause
Issue related to the keyboard or keyboard controller.
Solution
- Make sure the keyboard is connected to the proper port on the back of the computer.
- Turn off the computer and disconnect the keyboard and verify there are no bent, burnt or broken pins on the keyboard connector or on the keyboard connector on the back of the computer.
- Try a different keyboard on the computer.
- Unfortunately, if all of the above recommendations do not resolve your issue, the motherboardmay have a bad controller and will need to be replaced.
System timer failure
POST troubleshooting steps
Question
POST troubleshooting steps.
Additional information
This document is intended to help users who are experiencing issues with the POST and may have any of the below symptoms.
- Computer beeps irregularly when the computer is turned on.
- Computer turns on but does not boot or do anything.
- Computer reboots every few seconds.
Answer
Tip: Make sure the computer turns on, if nothing happens (no lights, no sound, no fans, etc.) the computer has a power related issue.
Caution: 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 ElectroStatic Discharge (ESD)and its potential hazards.
Remove new hardware
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.
Remove any disks or USB devices
Remove any disks, CD's, DVD's that are in the computer and if any USB devices (iPods, drives, phones, etc) are connected disconnect all of them as well. Reboot the computer and see if anything changes.
Disconnect external devices
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 keep the monitor or display connected to see if any change occurs.
Identify beep code
If you are receiving a sequence of beeps see the beep code page for a listing of different beep codes and their explanation or your motherboard or computer documentation. These beep codes are meant to help identify what computer component is failing or bad. If your beep code is not listed, continue troubleshooting.
Check all fans
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 or detecting the fan failure causing the computer not to boot.
Check all cables
Verify that all the cables are properly connected at that there are no loose cables by firmly pressing in each cable.
- All disk drives should have a data cable and power cable connected to them.
- Your power supply should have at least one cable going to the motherboard. Many motherboards may also have additional cables connected to them to supply power to the fans.
Disconnect all expansion cards
If the above recommendations still have not resolved the irregular POST, disconnect the riser board (if applicable) and 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 what card is causing the issue.
Disconnect all drives
If you were unable to determine by the beep code what is failing or do not have a beep code disconnect the IDE, SATA, SCSI, or other data cables from the CD-ROM, hard drive, and floppydrive from the Motherboard.
If this resolves your irregular POST or generates error messages re-connect each device until you determine what device or cable is causing the issue. In some situations it can also be a loose cable connection that causes the issue.
Remove the RAM
If you continue to to receive the same problem with all the above hardware removed, disconnect the RAM from the Motherboard and turn on the computer. If the computer has a different beep code or if your computer was not beeping and is now beeping turn off your computer and try the below suggestions. Making sure to turn off the computer each time you're adding and removing the memory and then turning the computer back on to see if the suggestion resolves the issue.
- Re-insert the memory into the same slot.
- If you have more than one stick of memory remove all but one stick of memory, try rotating through each stick.
- Try one stick of memory in each slot.
If you're able to get the computer to boot with one or more of the sticks of memory it's likely you're dealing with some bad memory. Try to identify what stick of memory is bad and replace it.
If you're able to get memory to work in one slot but not another slot. You're motherboard is defective you can either workaround the issue by running the memory in a different slot or replace the motherboard.
Power cycle the computer
In some situations a computer may have power related issues often caused by either the power supply or the motherboard. To help determine if this is the cause of your issue try turning the computer on, off, and back on as fast as possible, making sure the computer power light goes on and off each time. In some situations you may be able to temporarily get the computer to boot.
This should only be used as a temporary workaround if you're able to get this to work. Often this is good for users who may have not done a backup and need to get the computer up one more time to copy files before starting to replace hardware.
Disconnect and reconnect the CPU
For users who are more comfortable working with the inside of their computer or who have built their computer one last recommendation before assuming hardware is bad is to reseat the CPUby removing it and putting it back into the computer.
Bad motherboard, CPU, RAM, or power supply
If after doing all of the above recommendations you continue to have the same issue unfortunately it is likely that you have bad Motherboard, PSU, CPU, or RAM. The next step would be either to replace these components 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, CPU, and then power supply in that order or try swappable parts from other computers.
DRAM refresh failure
Computer has three short beeps as it starts
Question
Computer has three short beeps as it starts.
Cause
Computer RAM (memory) related issue.
Answer
Caution: 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. Information about ESD and proper grounding techniques are found on our ESD help page.
Remove added memory
If you've recently added or tried to add additional memory to the computer and have started getting these beeps. Remove all new memory you've added to the computer. If the computer works fine after removing the new memory you're encountering either an incompatibility or defective new memory.
Open computer and reseat memory
Sometimes when the computer is moved or over time a memory stick can become loose causing the computer to be unable to read the memory or get errors as it's reading it. Try fixing this issue by opening the computer removing each of the memory sticks you have in the computer and then placing them back into the computer.
Swap memory location
If reseating the memory did not resolve the issue try swapping the location of the memory. If you have only one stick of memory in the computer try moving it to another slot and then boot the computer.
If you have more than one stick of memory try removing all but one stick of memory and boot the computer. If this does not resolve the issue try removing that stick of memory and try one of the other sticks of memory.
Try another computers memory
If you have access to another computer that uses the same memory, try using its known good memory in your computer.
If another computers memory works you know that you have bad memory. If another computers memory does not work and it is compatible with your computer unfortunately your motherboardor the slots on the motherboard are defective causing it to be unable to properly read the memory, which means the motherboard will have to be replaced.
Replace memory
If it is determined the memory in the computer is bad we suggest that you replace it.
Computer POST and beep codes
POST ABCs
The computer power-on self-test (POST) tests the computer to make sure it meets the necessary system requirements and that all hardware is working properly before starting the remainder of the boot process. If the computer passes the POST the computer will have a single beep (with some computer BIOS manufacturers it may beep twice) as the computer starts and the computer will continue to start normally. However, if the computer fails the POST, the computer will either not beep at all or will generate a beep code, which tells the user the source of the problem.
If you're receiving an irregular POST or a beep code not mentioned below follow the POST troubleshooting steps to determine the failing hardware component.
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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 |
| 1 long, 2 short | Indicates a video error has occurred and the BIOS cannot initialize the video screen to display any additional information |
| Any other beep(s) | RAM problem. |
If any other correctable hardware issues, the BIOS will display a message.
Below are general 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. |
| 1 Short Beep | Normal POST, computer is ok. |
| 2 Short 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. |
| One Long and one Short Beep | Motherboard issue. |
| One Long and Two Short Beeps | Video (Mono/CGA Display Circuitry) issue. |
| One Long and Three Short Beeps. | Video (EGA) Display Circuitry. |
| Three Long Beeps | Keyboard or Keyboard card error. |
| One Beep, Blank or Incorrect Display | Video Display Circuitry. |
| Tones | Error |
| 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 and 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. |
| 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. |