LGA 771 Xeon Microcode – How to MOD Your BIOS



In this guide, we'll cover how to add the LGA 771 Xeon microcode to your BIOS. This is sometimes necessary for people doing the LGA 771 to 775 MOD.

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

How will updating the microcode help?

It can restore missing CPU instructions

If you did the LGA 771 to 775 MOD and notice missing CPU instructions (such as Speedstep, SSE 4.1, VT-x, or CompareExchange128) adding the Xeon microcode will usually restore that functionality.

It can also improve system stability

Microcode updates usually fix bugs or add new features, so by updating the microcode, you can sometimes make your system more stable.

LGA 771 Xeon microcode guides

Important: Make sure you do a FULL BIOS reset after updating your microcode.

If you have an Award, Phoenix, or AMI BIOS, the guides shown below should cover everything you need to know to add the LGA 771 Xeon microcode to your BIOS.

How can I tell what type of BIOS I have?

You may see the BIOS type when you turn on your computer or enter the BIOS. If you don't, you can use a program called CPU-Z to look this up (it should be listed as BIOS Brand in the Mainboard tab).

Note: AMI is short for American Megatrends Inc., so you may also see it listed the long way.

LGA 771 Xeon microcode files

Note: You don't need to download any of these files if you're using one of the guides shown above (they already have the correct microcode files).

  • 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).
    • Also contains the LGA 771 microcode shown below.
  • LGA 771 microcode

When you unzip one of these files, 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 (how to get the 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.

Note: If your CPUID ends in an "h" and you don't see 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.


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
  • cpu1067A_platB1_ver00000A0E_2015-07-29_PRD_59BF808E

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.

What to do if you don't have an Award, AMI, or Phoenix BIOS

Insyde BIOSes

If you have an Insyde BIOS, there's a more advanced guide on manually hex editting a BIOS to add microcode. It is available here.

Intel BIOSes

We don't currently know of any microcode updating guides for Intel BIOSes. We've also heard that Intel may be using a secure checksum to prevent people from modifying them. If this is the case, it would prevent the manual hex editing method used for Insyde BIOSes.

Dell BIOSes

Dell often makes their BIOS updates available in an .EXE file that cannot be extracted by regular unzipping programs, so you'll need to use the trick shown below to extract it.

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

You can extract the actual BIOS from a Dell .EXE file with the following command:

DellBiosFilename.exe /writeromfile

This needs to be done from a DOS command prompt window.

Other BIOSes

If you have a different type of BIOS, you may be able to update the microcode by manually hex editing the BIOS. If you're interested in trying that, read the Insyde BIOS modding guide.

You may need to update the microcode in multiple places

If you're hex editing your BIOS to update the microcodes, we've noticed that some BIOSes have the same microcode in multiple places. If that's the case with your BIOS, make sure you update the microcode in all of the locations. Otherwise, it may not work.

Where to go for help

If you have questions about updating an Award, AMI, or Phoenix BIOS, leave a comment at one of the guides mentioned earlier.

If you need help with a different type of BIOS, we recommend asking for help at the following places: bios-mods.com, overclock.net, or forums.mydigitallife.info.

196 Responses

  • blllll February 8, 20179:56 am

    Can anybody modify this bios to work ASRock > G31M-S x5450 help

  • Антон March 13, 20173:52 pm

    здравствуйте! Как мне прошить материнскую плату от компании acer под Intel Xeon E5450
    model: EG31M
    soket: LGA 775

  • Николай March 28, 20178:27 pm

    Здравствуйте. Помогите прошить Acer EG43M под Xeon 5460
    Hello. Help to stitch Acer EG43M under Xeon 5460

  • Eric March 29, 201712:13 am

    Hi has someone allready a working bios for the xeons on a p5kpl am in/gb. The one i downloaded does not work it says rom ID incomptible.

  • Eric March 29, 201712:14 am

    Hi has someone allready a working bios for the xeons on a p5kpl am in/gb. The one i downloaded does not work it says rom ID incompatible.

  • Dylan April 13, 20172:03 am

    Using an asus g41 chipset motherboard and want to squeeze out a little more juice from a x5460 (also get rid of the annoying update notification on boot even tho it’s the latest bios) but can’t find the bios file. I’ve tried taking the exact rom file from asus’s site and copy pasting the name into the search bar but nothing.

  • JanCerny April 15, 201711:47 pm

    Hello, I was gathered all microcodes for LGA771 and LGA775 platform. Some microcodes was released in 2015.

    You can download this package from Win-RAID.com forum:
    sha1: 95e9302c600daf0e4184096c99ab469b73dd2185
    package name: 2017-04-16-complete-LGA771-775-NetBurst-to-C2Q-45-nm-(most-updated).zip

  • Mirec May 4, 20175:21 am

    Hello, so much thanks for this guide ;) i have not had any performance or stability issues but still that message about unknown cpu detected was really annoying :) added microcodes and the message is gone. P5K deluxe + E5450

  • beloadi May 11, 20175:37 pm

    i use xeon E5440 on ASUS P5KPL-AM SE, How to activated all CORE (QuadCore). cause now only 2 core Activated while i use CPU-Z. sorry for my bad english.

  • Giovanni May 18, 20176:47 pm

    Please…help me … asrock g31m-vs2 and xenon e5450


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