How to Update CPU Microcode in an AMI BIOS – For LGA 771 & 775



In this guide, we'll show you how to update or add new CPU microcode to an AMI BIOS. If you have an Award or Phoenix BIOS, check out this guide instead.

Note: Microcodes are current as of 2018-12-02 (source). They were last updated by Intel on 2015-08-02.

Note: This information has only been tested with LGA 771 and LGA 775 BIOS files, so if you have a newer motherboard (especially UEFI ones), it probably won't work.

Why would you want to do this?

Updating the microcode is helpful if:

  • You did the LGA 771 to 775 MOD, and your Xeon is not working as expected (or is missing functionality, such as CompareExchange128, Speedstep, SSE 4.1, or VT-X).
  • Your BIOS doesn't support a newer processor that you want to run.
  • The microcode for your processor is old and may be buggy.


There's an element of risk just flashing a normal BIOS, and especially when you start modifying it, so please attempt this mod at your own risk (and only if you're experiencing some problem). We highly recommend that you don't flash the modified BIOS unless you've verified the microcode was added correctly. If you accidentally remove the microcode that your processor needs, your system may fail to boot. We are not responsible if your system is damaged while attempting this.

Things you'll need

Step 1 - Download the microcode for your platform

  • Desktop LGA 771 and LGA 775 microcode
    • If you're trying to add LGA 771 Xeon support to an LGA 775 motherboard, this is the recommended file to download. It will allow you to not only add the LGA 771 Xeon microcode to your BIOS, but you can also update your processor's similar LGA 775 microcode (which is probably a good idea).
    • Contains microcode for all Core 2 Duo and later desktop processors (no Pentium 4 or mobile support)
    • Contains microcode for all LGA 771 Xeon processors (except older Pentium 4 based 50xx models).
  • Desktop LGA 775 microcode
    • Contains microcode for all Core 2 Duo and later desktop processors (no Pentium 4 or mobile support)
  • Mobile LGA 775 microcode
    • Contains microcode for all Core 2 Duo and later mobile/laptop processors (no Pentium 4 or desktop support)
  • LGA 771 microcode
    • Contains microcode for all the LGA 771 Xeon processors mentioned earlier (no LGA 775 or mobile support)

Step 2 - Look up the CPUID for your processor

You'll need the CPUID to update the right microcode (how to get the CPUID).

What if I can't find the CPUID for my processor?

You can just update all of the microcodes.

Step 3 - Set aside the microcode files for your processor's CPUID

Note: If your CPUID ends in an "h" and you don't see a microcode with an "h" on the end, just ignore the "h" because it isn't actually part part of the CPUID. That just means it's a hexadecimal number.

When you unzip the microcode file, you'll see a bunch of individual microcode files that have filenames like this:


Here's what the different parts of the filename mean:

  • cpu0001067a - 1067A is the CPUID that is supported by this microcode
  • plat00000044 - plat is short for platform. This tells which sockets are supported by the microcode.
    • LGA 771 microcodes have a 4, 40, or 44 in this section
    • Desktop LGA 775 has a 1, 10, 11, B1, or 91
    • And for mobile LGA 775 it's a 20, 80, or A0
  • ver00000a0b - a0b is the version number
  • date20100928 - 2010-09-28 is the date the microcode was last updated

Which microcode files should I set aside?

You'll want to set aside all of the microcode files with your processor's CPUID. There should be at least one of these for each platform, and you should go ahead and update the microcode for all of the platforms that you want your motherboard to support.


So for our E5450 (E0 stepping SLBBM) with a CPUID of 1067A, here are the LGA 775 and LGA 771 microcode files with a CPUID of 1067A:

  • cpu1067A_plat44_ver00000A0E_2015-07-29_PRD_A3107D75.bin
  • cpu1067A_platB1_ver00000A0E_2015-07-29_PRD_59BF808E.bin

If you have that processor and want to add the LGA 771 microcode and update LGA 775 microcode (which is recommended), you'd want to set aside both of these files.

Step 4 - Open your BIOS in MMTOOL by using the "Load Rom" button

Note: MMTOOL will only open BIOS files that end in .ROM, so if yours doesn't, just rename it to .ROM for now.

mmtool cpu patch window

Having trouble finding the BIOS rom file that you need to MOD?

If your BIOS is in an .EXE format

You'll need to first extract it with an unzipping program like 7-Zip. Then look for a file that ends in .BIN, .ROM, or possibly something else like a number. LGA 775 BIOSes are usually around 1024 KB in size, so look for a file about that size. You can also try to open the file in MMTOOL. If it isn't the right file, MMTOOL will let you know.

How to extract the actual BIOS from a Dell .EXE file

Execute the following command from a DOS command prompt window:

DellBiosFilename.exe /writeromfile

This should extract the actual BIOS file to the same directory. When you're done modding the BIOS, you can use a program called AFUDOS.EXE to flash a Dell AMI BIOS.

Step 5 - Click the "CPU PATCH" tab to access the microcode area of the program

You'll then see a list of all of your current microcodes.

Step 6 - If you're updating your old microcode, delete all of the old microcodes that match your processor's CPUID

Note: MMTOOL only shows the last 4 characters of the CPUID, so don't let that throw you off.

  • Select the option "Delete a Patch Data"
  • Click the microcode you want to delete
  • Click the Apply button

If your Xeon's CPUID is 1067A, then delete all of the microcode entries with a CPUID of 067A (there may be more than one due to different platform types).

Step 7 - Insert the new microcodes

  • Select the option "Insert a Patch Data"
  • Click browse and select the microcode you want to insert
  • Click the Apply button

Do this for all of the microcode files that have your processor's CPUID. You should have set these aside in an earlier step.

What should I do if I'm getting an error message that there isn't enough room for the microcode?

You'll need to delete some of the old microcodes to make room. Just make sure you keep the microcode for your old processor in case you ever need to reinstall it.

The microcodes with a CPUID of 066x (where x can be any letter or number) are usually older Pentium 4 and Celerons, so those are usually safe to delete. You can also search for the CPUID on cpu-world to find out which processors use that CPUID.

Step 8 - Click "Save ROM as.." to save your modified BIOS

Step 9 - Verify that the microcode was added correctly

Go ahead and close MMTOOL, reopen it, and load your modified BIOS file, which you saved in the previous step.

Navigate to the CPU Patch tab again, and make sure all of the microcodes that you added earlier are shown.

You should also check to make sure no old microcode for your CPUID is present. If it is, you'll need to go back and delete it. Otherwise, your system may use the old microcode instead of the new ones we just added.

Step 10 - Update your BIOS using the modified ROM file that you just created

You should be able to update it the same way you'd update a normal BIOS.

Not sure how to update your BIOS?

The method for updating your BIOS is different for each motherboard manufacturer.

  • With some, you can simply put the BIOS file on a USB key, reboot and enter the BIOS, and update it from there.
  • Others may have a BIOS updating program that you can run from within Windows.
  • And in some cases, you may need to put the BIOS on a bootable DOS USB key, CD, or DVD and update it from a command prompt.

If there's a Windows or DOS BIOS updating program, it will usually be included with the BIOS or mentioned when you download the BIOS. If you don't see it, check the downloads section, FAQ section, or support section.

If all else fails, try searching Google for your motherboard’s model and update BIOS or something like that.

Step 11 - Do a FULL BIOS reset (use the 3-pin motherboard reset jumper, and then load the default BIOS settings on the first startup)

How to fully reset your BIOS

263 Responses

  • Tico June 20, 20195:40 pm

    Hi Folk, i Need a Bios Rom for (MS-76716) P55 , how to find for AMI Bios !??!
    i hope anywhere can help. I want to push my System to 32 GB Ram…. now ist 10 gb

    • Iwrg February 7, 202010:23 am

      Just backup your own current bios using Universal Bios Backup Toolkit

  • aratz June 27, 20194:48 pm

    hello, I have an asrock g31m-gs, according cpu-z t in the Instructions section I have: MMX, SSE, SSE2, SSE3 and EM64T, I think I need more, my bios is the latest version 1.90, and I can not extract my bios to add the missing microcodes, I follow the manual again and again and I do not advance, any help?

  • gorgor June 27, 20196:40 pm

    add .ROM at the end of your bios file. Not sure if you need to delete .ROM after editing and saving..

  • aratz June 28, 201910:47 am

    got! Thank you
    the problem was that I could not find the bios file, so I downloaded all types of bios, first for windows, second for Ms-dos, and third for Instant Flash, I tried to change all downloaded by .Rom, and finally it worked the file that was in Instant Flash, this download gave me a file called G31M-GS1.90 of type “.Archivo 90”, this file is changed by type .ROM and finally opened in mmtools.

  • Domin July 21, 20195:06 pm

    I am looking for a ready-made bioson for the E5462 motherboard Gigabyte EP45T-UD3LR ev 1.0 bios award

  • Domin July 21, 20195:07 pm

    I am looking for a ready-made bios for the xeon E5462 motherboard Gigabyte EP45T-UD3LR rev 1.0 bios award

  • Thenoob114 September 28, 20196:04 am

    Hi I am having a very hard time trying to get this lga775 to 771 mod to work. I would appreciate it if someone with more knowledge can help me.

    > I have a Asus P5QL-PRO motherboard (it appears to be a 65nm board and has a p43 chipset)
    > I am trying to get a Xeon E5450 (SLBBM) to work.

    According to Aida64 my CPUID revision is (CPUID Revision 00000F65h) I have looked everywhere in the zipped file provided ,but I can’t find it .

    I would be very grateful to anyone who can help me and as the name suggests I am very green in the microcode department.

  • Jason November 15, 20191:34 am

    This week I successfully installed a Xeon E5420 in an Asus P5G41T-M LX motherboard. I updated the bios with the Xeon cpu microcodes before installing the Xeon cpu and reset the bios. (Previous cpu was pentium dual core). Windows 10 Home was already installed and I had no issues after bios reset and reboot. (Don’t forget to check time/ date and SATA mode settings in bios after reset).

  • Henry April 9, 20201:06 pm

    Hola amigo tengo un computador Lenovo Thinkcentre M57 con chipset Q35 Lga 775, podría ser posible instalar un procesador Xeon x5420 cambiando los microcodes?

  • Des May 17, 202012:13 am

    Здравствуйте, я прочитал и это всё трудно усваивается, помогите собрать подходящий микро код под материнскую плату Asus P5Q SE ID системной платы 64-1005-000001-00101111-071009-Eaglelake$A0985001_BIOS DATE: 07/10/09 14:51:47 VER: 08.00.14
    Для процессора X5460 SLANP
    Буду благодарен за помощь человеческим СПАСИБО!!!


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