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

  • Inder September 28, 20143:16 am

    I need help with my motherboard p5g41t-m lx3
    I am able to run Xeon 771 e5440 processor but I get message to unleash the full power update the bios
    So any one please????

    • syn September 28, 20144:49 am

      Hey, if you add the LGA 771 Xeon microcode to your BIOS (as explained on this page), it should get rid of that error message.

  • Inder September 28, 20142:05 pm

    I will try how to get bios. Do I have to download from website of motherboard in this case asus

  • inder September 30, 20147:26 pm

    i did how it is shown
    i have e5440
    so i upload both micocodes in bios still same question
    unleash the cpu power bios update


    • syn October 1, 20144:27 pm

      If it’s still giving you the error message, then the microcodes weren’t updated correctly. I’d try reading the directions again to make sure you didn’t miss a step.

  • Lumen October 1, 20149:36 pm

    I’m stuck, it won’t let me open the Rom File. I’m using Dell T3400 A14 Bios.

    It says Error Loading Rom Image (100003h)

    • syn October 2, 20142:28 pm

      With Dell, you usually have to extract the rom file from the Dell .EXE like this:
      filename.exe /writeromfile

      Once you’re done modding it, you can then use AFUDOS.EXE to flash an AMI BIOS.

      • Lumen October 3, 20141:21 am

        I’ve used the Writeromfile command – it extracts a rom file, but it won’t read.

        • syn October 3, 20142:16 pm

          Are you positive it’s an AMI BIOS (you can check this with a program like CPU-Z or AIDA64 if it doesn’t say AMI when you turn on your computer)? Dell sometimes has their own custom BIOS.

          If it isn’t a standard AMI BIOS, you could try the manual Insyde BIOS hex editing method mentioned here:

  • inder October 2, 20142:33 am

    yes its working now thanks alot for the help.
    it is very easy to do that !!!!!! i didnt add all .bin files
    its working nicely now

  • Gabi October 4, 20146:47 am

    I have an ASRock G31M-S R2.04 motherboarb with latest BIOS and E5450 SLANQ CPU with mod, the BIOS shows me the CPU but Windows is not loading. It gets stuck at Loading Windows… I tried updating the microcodes for this CPU same thing… Can you please tell me what to do?
    Thank you for your time!
    Best Regards,

    • syn October 5, 20142:52 pm

      Hi, I recommend trying the SATA hard drive mode stuff mentioned here:

      • Gabi October 5, 20145:12 pm

        Hi, I have 2 HDD one SATA with Windows 7 and one IDE with Windows XP, none of them will boot. I tried to reinstal Win 7 from USB the instalation won’t even start, same gets stuck at Loading Windows. I even replaced the PSU and nothing. With my old Dual Core CPU there is no problem.

        I don’t know what to do anymore… tomorrow I’ll try to lower the multiplier and increasing the voltage abit. Is it possible that E5450 CPU to be bad? I bought it on EBay and I’m a little worried.
        Thank you for your time!

        • syn October 5, 20147:32 pm

          If you’ve tried everything in the troubleshooting section (like fully resetting the BIOS, loading the default BIOS settings, adding the LGA 771 Xeon microcode to the BIOS, etc.), then, yes, your adapter or Xeon could be defective. However, make sure that you’ve tried all of the previous stuff before assuming that.

        • syn October 5, 20147:36 pm

          You may also want to check your RAM timings, speed, and voltage. I’ve heard of it getting reset to the wrong values when resetting the BIOS.

          And make sure your BIOS was FULLY reset as explained here: Most people that have problems haven’t done this right.

  • Gabi October 9, 20142:24 am

    RAM timigs, speed and voltage are set to auto, I’ve reseted the BIOS both ways removed the battery for about 1 minute with the PC unpluged and with the jumper, same thing. I downclocked it, multi to x6 and FSB 266, nothing… I did a google search and find pics of someone else with the same MB who made this mod and noticed Vcore to 1.0V, but I can not change Vcore from BIOS, mine is set to 1.232V

    • syn October 9, 20142:42 am

      Auto may be choosing the wrong ram values, so I’d try setting it manually. If that doesn’t work, I’d try another adapter.

    • syn October 9, 20142:48 am

      Did you also go into the BIOS and load the default settings?

      • Gabi October 9, 20143:01 am

        Yes, first thing when I reset the BIOS I load the default settings

  • Miguel October 16, 201411:46 am

    ii is possible on this MB Asrock G41M-VS3 or MSI
    G41M-P33 Combo?

    • syn October 18, 20149:42 am

      Yes, this MOD should be possible on both of those motherboards, and if they have an Award, AMI, or Phoenix BIOS, you should be able to update the microcode using the guides on this site.

  • Dk October 21, 20144:29 am

    Hello my board is ibm 8114dd5 its a d945 witk LGA 775 but it is restricted to pentium d only which frustrates me alot. Can I use your method to run core 2 duo processor on it? Or its just a different thing what I am thinking?

    • syn October 21, 20147:59 am

      I couldn’t find any info on your motherboard, so there may be typo in the model number. Adding the microcode is mainly geared toward updating the microcode when the motherboard maker got lazy and never issued an updated BIOS.

      If the northbridge chipset in your motherboard supports the processor you want to run, updating the microcode may make it work, but it isn’t a guarantee. You can check what processors your chipset supports here:

      • bazil October 21, 201412:00 pm

        yup its listed there that my D945 chipset can supports core 2 duo and even Intel’s website says that this board (or chipset) is core 2 duo supported. but unfortunately on IBM’s website, specs says that the highest processor it supports is pentium D 3.4 ghz. i have tried a core 2 duo processor on it but what happens is that the fan runs to full speed and nothing else. so what do you suggest should i give it a try?

        • syn October 22, 201410:15 am

          Since the chipset supports it, I’d try adding the microcode for the Core 2 Duo processor you want to run.

  • bazil October 21, 201411:48 am

    hey ya! i m really frustrated with my motherboard i have an IBM 8114 motherboard which is D945 with socket 775 but it is restricted to pentium 4 and pentium D processors only, so can i use your method to make my motherboard run core 2 duo processors? as i have understood or what i m thinking is different?


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