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

  • NiksAllCaps March 25, 201812:14 pm

    Hi, I have a Asus P5G41T-M-LX3 motherboard upgrading from Pentium E5700 dual core @ 3.0Ghz to Intel Xeon X3323 quad core @ 2.5Ghz (which I bought from Aliexpress already modded to fit 775 socket). I have already upgraded the bios to its latest version and yes the new processor works I can do things normally, play games, surf the internet, watch media, do word processing without any problems as of now but there is this message that says “To unleash the full power of this CPU, a bios update is needed”. SMH, I already updated the bios to its latest version, reflashed the bios but the same thing happens again. What can I do to remove this message during post? Do I need to add microcodes to my bios for this message to disappear? Any help is appreciated. Thanks

    • Julianus July 7, 20188:07 am

      I had exactly this problem, I have a p5p41t and an e5450, I followed the tut and the 10 sec warning in the boot is gone.

  • Baassbooster March 28, 201810:29 am

    Hi im having trouble opening microcode that you included under lga 771 downloads in MMtools
    I have ASUS P5Q Pro motherboard and XEON 5450 C0 10676h proc.It sais ERROR loading rom image (100000h). Bios AMI vrsion 2102 date 23/2/2009

    • Baassbooster March 29, 20185:47 am

      Ok i fixed it and found a solution on this site

      • someone April 1, 20186:36 am

        Are the microcodes already injected in the bios on the site??????

      • someone April 1, 20186:41 am

        email me plz plz plz

        • Baassbooster April 1, 20187:03 am

          Yes they are

  • someone April 1, 20186:30 am

    I have a MSI G41M-P33 COMBO with AMI bios. I cannot load the rom in mmtool. The bios from is in .WD0 format……… Please help

  • Devan June 2, 20186:58 pm

    when I try and open the modded bios Command prompt pops up and trys opening it in MMtool

  • Devan June 2, 20187:13 pm

    Got it to opein with AMI firmware update tool but it says warning unable to unload driver, worried about restarting the computer

  • Devan June 2, 20187:25 pm

    mother board is an HP IPIEL-LA

  • Juan August 9, 20184:08 pm

    amigos por favor la bios de mi placa gigabyte g41m combo version 2.0 es un archivo “.fa” no es un archivo “.rom” por favor ayudame, yo cambie la extension pero el mmtools no reconoce aun con la extension cambiada.

  • Bijou August 14, 20181:40 am

    thx for your tutorial it was well explained . I have a core 2 duo e7500 2.9ghz on mobo abit il9pro.The problem is that it was running only at 1.6ghz even with latest bios.even after adding support for this cpu which id is 1067a it stills run at 1.6ghz.i even disable step speed in bios plz help me!!!

  • sanjinreloaded August 24, 201811:47 am

    I have biostar g41d3c ver.7 i want add q6600 cpu i want a mod for it and any one provide me one?

  • fknmeeha September 7, 20182:38 pm

    Need help!
    very cool mod, decided to do it for an old build after watching a video on youtubes. I have a Gigabyte GA-P35-DS3L motherboard, and installed a Xeon X5460 cpu. Unfortunately, the Gigabyte update file is not .ROM format, and after searching for hours, I could not find a way to convert their .F9 file to the .ROM format. And simply renaming does not work, MMTool is unable to recognize the file.

    In the meantime, I have updated the bios to latest .F9 version using @bios, and booted the computer. The computer is usable, everything appears to operate normally. However, the bios & windows are only recognizing 2 of the 4 cores. I believe this is due to not being able to install the 771 microcodes.

    What can I do? How can I convert the gigabyte .F9 bios to .ROM format?

    • fknmeeha September 7, 20183:22 pm

      After reading thru all the comments (all the way back to pg.1), I think I have an AWARD type bios. So now I’m following this guide:
      Will post again if I have more questions. Thank you!

    • fknmeeha September 7, 20188:03 pm

      I’m having a similar problem following the AWARD bios steps. Using Method 1, on “Step 3 – Rename the microcode file to ncpucode.bin and make it readonly”. Renaming the file makes it unreadable. Then “Step 4 – Delete the old microcode and replace it with the new code” does not work. cmd sats ” ‘cbrom195.exe’ is not recognized…”

      What to do from here?

    • Anonim December 30, 202010:51 pm

      Hey, i have same mb like you, but i use xeon l5420. Now, i still confused to update the bios. So, what you do to fix that?


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