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: 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, or 11
    • 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:

  • cpu0001067a_plat00000011_ver00000a0b_date20100928.bin
  • cpu0001067a_plat00000044_ver00000a0b_date20100928.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.

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.

mmtool cpu patch window

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 and that the date on them is from 2010 (which is when Intel last updated them).

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.

I'm not sure how to update my 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

206 Responses

  • Donald March 7, 201612:34 pm

    I have 3 systems that I would love to make work with a Xeon. All Dell unfortunately. Optiplex USFF 755 & 760 and a Vostro 220. All have C2D processors. I have extracted the ROM file from my 755, but the tool won’t open it, I just get an error.
    Is there anyone that would be willing to do this for me? I have a Xeon X3323. I was told the Optiplex 755 & 760 already are compatible, but neither will boot with the processor. I know the processor is good because I have a server system that runs fine with it. Yes, the mods on the board has already been done and the adapter sticker is in place. Any Help Appreciated!

  • Boudewijn April 29, 20165:40 pm

    Thank you for taking the time to make such a detailed explanation in what to do and how it works.

  • Jack May 21, 201610:12 am

    Please tell me, how can i mod BIOS that have .BIO format? Just rename it to .ROM??
    My Motherboard – Intel DG33BU

  • DANIEL July 17, 201612:04 pm

    hello good afternoon, I would take a doubt, I will take a xeon x3363, and also one asus p5qle, q I will do all these procedures? or just I go on the asus website and download the latest BIOS and use? or I q modify the bios file placing the microcode? hugs

  • Sparticle July 19, 20167:07 pm

    Can anyone provide a modded bios for a Xeon L5430 please. The motherboard is an ASUS Striker II Extreme that is on the tested motherboard list. The latest BIOS is 1402

    The L5430 is a 1067a processor.

    Any help appreciated. I am keen to see if we can get this board working with an L5430 Xeon.


  • ym58 July 25, 20169:29 am

    My MoBo is MSI G41M-P33 combo.

    I have purchased a Xeon X5450 processor (Sspec : SLASB – Stepping : C0 – CPUID : 10676) and put a LGA771>>>LGA775 sticker on it.

    I have also implemented the following micro-codes to the MSI G41M-P33 latest BIOS :

    After I flashed the BIOS, cleared the CMOS (jumper short ***and*** battery removal) and then rebooted the machine … it’s NOW AWFULLY SLOW !

    Taking more than 15min to reboot and windows operations are VERY VERY VERY sluggish.

    I finally had to replace my X5450 with another entry-level X3040 and now it works again just like before …

    Would anyone have any clue/hint how to make the X5450 proc work at “NORMAL SPEED” on this MoBo ?

    Needless to say that this MoBo has already been tested as OK for an X5450 upgrade (as stated here : )

  • graham August 12, 20164:03 am

    hi bud I have the x5470 cpu I installed the microcode and it worked perfectly however since switching from windows 7 to windows 10 grand theft auto now has severe texture pop ins problem I can get round it by setting it as high priority but I cant live stream well with it like that. do u know of any new microcodes for this cpu? is there anything specific for windows 10? mobo ASUS P5Q-E

  • BigProblem August 12, 20162:33 pm

    Where to find ” something.ROM ” ? When i extract gigabyte file i have 3 files, autoexec (windows batch file), FLASHSIP (application) and P31ES3G.F6 . When i rename P31ES3G.F6 in P31ES3G.ROM, not possible to load in tool. What to do?

    • solarflare January 31, 20177:08 pm

      I chave now the same problem, did you find the solution?

    • solarflare January 31, 20177:08 pm

      I have now the same problem, did you find the solution?

  • Siom September 11, 201610:52 am

    my motherboard is msi g31m3-f and when i changed my old procesor for new xeon e5450 my pc isnt working i just get to the wimdows logo and under it is text something about automatic repair. i thought it can be because i havent updated bios jet so i wanted to add those microcodes cpu0001067a_plat00000011_ver00000a0b_date20100928.bin
    but it is saing taht they are alredy there, but they are from 2007 not 2010 and when i delete them and add those which i downloaded it still are from 2007

    • 79pots September 30, 20167:40 am

      If you changed your CPU and resetted BIOS settings and PC turns on, that message might be caused because SATA mode might have changed, so check that out in BIOS

      And for the BIOS uCods, maybe it’s locked

  • modforMe September 20, 201610:57 pm

    I have posted my problem updating my ami-bios rom for Gigabyte mobo here, using mm-tool. I cannot find my post here, let alone an answer for it… What happened?


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