LGA 771 to 775 Adapter (MOD) – Run faster Xeon CPUs in a Core 2 Quad motherboard



Motherboard Compatibility

There are two requirements that your motherboard must meet in order to be able to run LGA 771 Xeon processors:

  1. You must have an LGA 775 motherboard with a compatible chipset.
  2. Your bios must support an LGA 775 CPU that's similar to the Xeon you want to run.

We'll explain how to verify these things in the sections below. And later in this guide, there's also a list of motherboards that have been tested with this MOD.

First, make sure your motherboard's chipset is compatible

The chipset we're talking about here is technically called the Northbridge chipset. You can usually find what chipset your motherboard has by looking at its specification list.

Chipset compatibility table

Note: For known compatibility issues and more details, please see the bullet points (which are shown right after the table).

Xeons that are compatible with each chipset
Chipset5xxx Series3xxx Series45nm65nm
P45, P43, P35, P31, P965
G45, G43, G41, G35, G33, G31
nForce 790i, 780i, 740i, 630i
GeForce 9400, 9300
Q45, Q43, Q35, Q33
X48, X38
nForce 680i and 650iYesYesMaybe
(see below)

If you don't need more details about the topics shown above, you can skip ahead to the next section: Next, make sure your BIOS supports a similar LGA 775 CPU.

What do 5xxx series and 3xxx series mean?

By 5xxx series we mean any Xeon whose model number ends in 5xxx (this includes all the E5xxx, X5xxx, and L5xxx processors).

Issues with Intel brand motherboards

Note: This information only applies to motherboards actually manufactured by Intel. We haven't heard of any problems with ASUS, Gigabyte, MSI, or any other brands.

Some motherboards made by Intel don't work with this mod

For some reason, some Intel brand motherboards that have a compatible chipset and support a similar LGA 775 processor do not work with this mod (please see the list of tested motherboards for the model numbers).

It may not be possible to update the CPU microcode on an Intel brand motherboard

This is sometimes needed to install Windows 8.1 64-bit or to enable all of the CPU features (like Speedstep, SSE 4.1, or VT-X). The older non-E0 stepping processors often don't need a microcode update to enable these features, so if you do try it, buy one of those.

The reason this may not be possible is because Intel has their own proprietary BIOS that nobody currently knows how to MOD (even by manually hex editing the BIOS).

Nvidia's nForce 680i and 650i chipsets don't officially support 45nm quad core processors

Some motherboards with these chipsets have worked with 45nm quad core Xeons, and some haven't (please see the list of tested motherboards for more details). This is likely due to some motherboards unofficially supporting 45nm quad core processors.

My chipset isn't listed here. Will this work for my motherboard?

The mod will still likely work if your BIOS supports a similar LGA 775 processor.

If you do try it, please let us know how it goes by leaving a comment at the bottom of this page.

Our guess as to why some chipsets don't support the 5xxx series Xeons (but do support the 3xxx series)

Xeons with model numbers that end in 5xxx are allowed to be used in motherboards that support 1 or 2 physical processors (this is called dual-processor support). However, the 3xxx series Xeons cannot be used in a multi-processor system (they're labeled as supporting uni-processor configurations only).

The E0 stepping E5440 and X3363 Xeons both have the same CPUID (1067A), which means they're both made from the same silicon and are basically the same internally. Additionally, there's no noticeable difference between them (other than one has dual-processor support), so it looks like this could be causing the problem. Some chipsets may be checking for this and may be blocking the system from booting.

Next, make sure your BIOS supports a similar LGA 775 CPU

Important: Make sure you only buy Xeon processors with a FSB and TDP supported by your motherboard.

How the compatibility table shown below works

Hopefully the table shown below is pretty self explanatory, but here's an explanation if it isn't. Each row shows an LGA 775 processor in the 1st column. If your motherboard and BIOS support that processor, you can run the LGA 771 Xeons shown in the second column (if your chipset supports it).

You should only buy Xeons with a FSB and TDP less than or equal to the values shown (unless your motherboard supports higher).

If your motherboard and BIOS support the following CPU:You can run these Xeons (if supported by chipset):Max FSB
(unless motherboard supports higher)
(unless motherboard supports higher)
Core 2 Quad Q9650Any 45nm quad core Xeon133395WView Xeons
Core 2 Quad Q9550SAny 45nm quad core Xeon with a TDP of 65 W or lower133365WView Xeons
Core 2 Quad Q6700Any 65nm quad core Xeon106695WView Xeons
Core 2 Duo E8600Any 45nm dual core Xeon133365WView Xeons
Core 2 Duo E6850Any 65nm dual core Xeon133365WView Xeons

For a list of all the compatible Xeons, their features, and current prices, visit this page.

If you don't need more details about the topics shown above, you can skip ahead to the next section: Recommended LGA 771 Xeon processors.

Some Xeons have a higher FSB or TDP* than their similar LGA 775 CPU

* TDP is a measure of how much heat your processor's cooling system will have to handle.

Because of this, you need to make sure your motherboard supports the FSB and TDP of the Xeon you're buying. Some motherboards will not boot processors with a TDP over 95W (or 65W for low power boards).

TDPs for some common Xeon processors
  • L54xx series has a max TDP of 50W
  • E54xx series has a max TDP of 80W
  • X54xx series with a 1333 FSB has a max TDP of 120W
  • X54x2 series with a 1600 FSB has a max TDP of 150W

How to check what TDP your motherboard supports

Our list of tested motherboards (shown later in this guide) has max TDP numbers for many motherboards, so you should check there first.

If your motherboard isn't in our list, a good way to check if your motherboard supports 120W and above processors is to check its CPU support list. If your system supports overclocking or extreme edition processors (like the 130W QX9650), you should be able to run the 120W X54xx series Xeons (the 150W ones will also probably work). However, if your system only supports the 95W Q6600 with a G0 stepping (and not the 105W B3 stepping), your system may only supports 95W and lower processors.

If you aren't sure what TDP your motherboard supports, I'd recommend going with the 95W and lower Xeons only.

How to check what LGA 775 processors your motherboard supports

If you're unsure what LGA 775 processors your motherboard supports, please read the following article: How to Check if Your Motherboard Supports a Specific Processor.

Be careful if you have a prebuilt system (like a Dell)

Prebuilt computers (like Dell) sometimes use different motherboards (depending on what parts come with the system), and the motherboards may not support the same processors, so you'll need to figure out which motherboard you have.

You should be able to find the model number with CPU-Z.

Right now, the following 45nm Harpertown Xeons with a 1333 FSB seem to be the best deals. These are quad core and have high multipliers (ratios), which means they should also overclock easily.

For more prices and detailed specs on all of the Xeons, visit this page.

1,718 Responses

  • atechol June 17, 20174:02 am

    Hello everyone.
    I have been researching the 771 to 775 mod for awhile now and just wanted to say thanks for all the information you guys have put together here.

    • Han Solo June 17, 20175:22 pm

      I have done this twice. And I have to say to me it is much easier to just take a small round file and file some notches into the XEON CPU using an old core2 as a template. It is very easy to mess up the pins on the socket trying to get the plastic tabs out of there and you can take your time with the file and do a pretty neat job with not much effort.

  • atechol June 17, 20174:05 am

    Bbtw, I just successfully installed an x5450 in a HP Pro 3000 Microtower with the information found here. Thanks Again!!!!

  • paul ferguson June 17, 20179:23 am

    Just finished the mod with a Asus P5K PL SE and a X5460 ,all running OK but like a few other posters have said in order for windows and various programs to identify the Xeon and not keep reporting my old Core duo 8500 i installed the new bios 3 times and did 3 resets and load defaults .

  • Han Solo June 17, 20175:23 pm

    I have done this twice. And I have to say to me it is much easier to just take a small round file and file some notches into the XEON CPU using an old core2 as a template. It is very easy to mess up the pins on the socket trying to get the plastic tabs out of there and you can take your time with the file and do a pretty neat job with not much effort.

  • Peter June 19, 201710:57 am

    Confirmed work x3323 with Dell Optiplex XE SSF

  • Tina June 19, 20176:02 pm

    Thank you very much for all of this usefull information !

    I am not trying to fit a LGA771 CPU into a LGA775 board, so please excuse my question.

    I want to mod my two (dual) X5365 Xeons with this BSEL in my 771er board.

    1. What can I expect when doing this ? Does this hoover the FSB ?

    2. My board has an Intel 5000x Chipset and my two X5365 Xeons are listed as the biggest
    supported Socket 771 CPU’s. What about the newer 54xx Xeons ( only those for LGA771
    with the same matching FSB ) Do these also fit into Socket 771 and work ?

    Cheers Tina

  • Domenico June 22, 201712:48 pm

    Hi to all, i just want to know if Xeon E5472 (FSB 1600, TDP 80W), Xeon X5460 (FSB 1333, TDP 120W) and Xeon E5450 (FSB 1333, TDP 80 W) are compatible with my MoBo Asus P5G41C-M LX (FSB 1333, TDP I don’t know)

  • Vegethalia June 23, 20173:10 am

    Hi, tested successfully a xeon X3360 with an Asus P5E3-Deluxe.
    Easily overclockeable to 3.2ghz+ with stock voltajes.

    Thank you!

  • atechol June 23, 20174:55 am

    HP Pro 3000 MT Pine Row Motherboard Xeon X5450 Mod.
    I posted earlier this week saying this mod was successful and it was. After spending several days loading software (50 games) and all other software. I noticed that the processor was reporting differently on several programs. It would post Xeon X5450 @ 3000 MHz , then showed 2333 MHz behind it. Turns out that the old bios was holding it’s multiplier at 7 instead of letting it run at 9. I followed the instructions for updating the AMI bios here on the site, modded the bios file and flashed it, reset the jumper pin and booted. After resetting my bios settings on the second boot all is well now. For anyone looking for a cheap gaming solution, this combo with 8 gb ddr3 10600, a 450 watt psu and an XFX R7800 Ghost (HD7870) makes for a quite capable gaming machine. You will need to adjust some settings but this lil machine is running Doom, Fallout 4, Skyrim, Sniper GW3, Deus Ex, ETC. Once again thank you to everyone who keeps this site updated and to those of you who have posted your experiences with these mods. I would have never attempted it, let alone completed it, without your help. Thanks Again.


Leave a Comment

Problem with this MOD? Please read the troubleshooting section before reporting a problem. If that doesn't help, please tell us all of the things you've already tried.

Unsure about compatibility? Please read the motherboard compatibility and tested motherboards sections of this guide.