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



If you're looking to extend the life of your LGA 775 system, there's an adapter available now that will let you install faster (and usually cheaper) Intel Xeon processors (LGA 771) into a Core 2 Quad motherboard (LGA 775). These Xeons cost a lot less and are basically identical internally to the high-end Core 2 Quad CPUs.

List of LGA 771 & 775 CPUs + Current Prices

The pages shown below should help with comparing Xeon prices and specifications. The first link has all the LGA 771 and LGA 775 CPUs combined into 1 table (sorted by price), and the others are the original uncombined pages.

Where can I get an adapter?

Here's a current list of eBay sellers (sorted by price). The sellers are located all over the world, so you should be able to find one that's close to you, and most of them will also ship worldwide.

Why would you want to do this?

Xeons are usually MUCH cheaper

For example, the Xeon E5450 is equivalent to a 3.0 GHz Core 2 Quad Q9650, and it currently costs about $6 on eBay (usually much less than the Q9650).

Other good deals on LGA 771 Xeons include:

For detailed specs on all of the Xeons and a full list of current prices, take a look at this page.

Xeons also typically overclock better

Additionally, if you’re interested in overclocking (making the cpu go faster than its default speed), Xeon processors are usually made from the best silicon, so you can typically achieve higher overclocks with them.

Someone that recently did this mod successfully overclocked a Xeon X5470 from 3.33 GHz to 4.5 GHz on an ASUS P5Q PRO motherboard, so you can achieve really good results with these Xeons.

How does the adapter work?

The adapter is basically an electronic circuit on a sticker, and you place it on the Xeon processor (as shown in the picture below). This switches two of the pads on the bottom of the Xeon to make it compatible with a Core 2 Quad motherboard.

Xeons that are compatible with this adapter

This adapter is only compatible with LGA 771 Xeon processors. If you're unsure what LGA 771 means, it's the name of the CPU socket used in some Xeon motherboards. And in comparison, LGA 775 is the name of the socket used in Core 2 Duo/Quad motherboards.

LGA 771 to 775 Adapter

Minor modification to the LGA 775 socket is also required

If you look at the LGA 775 socket in the picture below, you'll notice two tabs are circled in red. These tabs are there to stop you from installing a non-LGA 775 processor, and they'll need to be fully removed before you can install an LGA 771 cpu.

The tabs are pretty easy to remove if you have a sharp utility knife or box cutter (just be careful not to damage or bend any of the socket pins near the tabs).

Important: Make sure that you fully cut off each of these tabs. If they're not fully cut off, the processor may not align or seat correctly in the socket, which will stop it from making contact with all of the pins. If this happens, your system will likely fail to boot.

Once the tabs are cut off, you can use tweezers to safely remove the pieces from the socket.

The socket will then support LGA 771 or 775 processors (you can still reinstall your old processor if you ever need to).

Tabs to removed from the LGA 775 socket

2,484 Responses

  • Roberto Nelson December 17, 20133:06 am

    How would I know this sticker circuit wont just melt down or burn out after a couple of months? How good is the quality of this circuit?

    • syn December 17, 20133:43 am

      People have been doing this mod since around March of this year, and I haven’t heard of any problems with adapters failing months down the road.

      Since the adapter is applied to the bottom of the cpu, it isn’t subjected to the high temperatures found on the top of the cpu, so heat also shouldn’t be an issue.

      I’ve had a Xeon running overclocked (which means even more heat and voltage than normal) for months, and it still runs great.

    • someone February 4, 20168:08 am

      It’s 2016 now, are you US or EU still playing with 771? Even 1366 has already been abandoned here.

      • Retro Science February 24, 201712:29 am

        Yes, old tech is great and these beauties still have plenty to offer.

        • PaulieLUL November 6, 20182:09 am

          I agree, 775 and 1366 are still fun sockets

  • Roberto Nelson December 17, 20133:25 am

    I currently have an ASUS P5N-D

    It supports the Core 2 Quad Q9650(rev.E0,3.00GHz,1333FSB,L2:12MB) and the Core 2 Quad Q6700 (2.66GHz,1066FSB,L2:2X4MB,rev.G0,4 cores). In theory the mod should work. The question is, how hard is it to actually cut off those plastic parts on the motherboard? Is it really that easy now? I am just concerned, because this all sounds convincing but the actual work of having tu cut off plastic near those socket pins seems kind of risky…

    • syn December 17, 20133:46 am

      The plastic tabs come off pretty easily as long as you have a sharp utility knife. The only time I had a hard time was when I was using an old rusted box cutter that was dull.

      You do have to be careful around the socket pins, but if you are, it should go fine. I haven’t heard of anyone bending any pins.

      • Roberto December 17, 20136:54 am

        I’ll give this a shot, but I may have trouble with the BIOS. The thing is I don’t know what BIOS I have because I have never put any CPU on this board. I may have to buy a very cheap processor just for the BIOS update…
        I got the Intel Xeon X5450 3.0 GHz, which has a TDP of 120W. I am not sure what that means, but I sure hope it doesnt mean I’m having major heat issues. I do not plan to overclock. Would a regular and cheap fan/heat sink suffice?

        • syn December 17, 20139:40 am

          TDP is a measure if how much power the cooling system will need to dissipate.

          With the X5450, you’re supposed to buy a heatsink and fan that’s rated for 120W or above. Now, realistically, I’m not sure if you’d run into problems with a regular cheap fan/heatsink if you aren’t overclocking or running stress tests or something, but I’ve never tried it, so you’d be taking a risk.

          The E5450 is probably better if you’re wanting to run with a cheap heatsink/fan, since it’s rated at 80W.

          • Roberto December 17, 201310:04 am

            Hmm, yes I don’t know how this stuff works, but it would suck if the CPU pulls 120 Watts and that somehow burns out the Motherboard since its not a server-grade motherboard, but perhaps I could download some sort of CPU wattage/temperature monitoring software, and if stuff is looking bad then perhaps I could under-clock the CPU. I’ll wait and see what happens. I don’t plan to use that computer for gaming anyway. I think this motherboard has “Energy Saving Mode”… so maybe if I activate it it will put some sort of limit on the CPU or something. I’ll come back and post what ever ended up happening. I also got 4 dollar back up Celeron processor just in case.

        • syn December 17, 201310:19 am

          Your motherboard also supports a QX6850 (which is 130W), so the 120W definitely won’t damage your motherboard.

          My guess is that the X5450 may use slightly more power than an E5450 (due to probably using a slightly higher voltage), but I doubt it will come close to needing 120W. It’s identical internally to the E5450 (same stepping and everything), so Intel is probably just being conservative. However, I haven’t personally used any of the X5xxx Xeons, so this is just a guess.

          • Roberto December 17, 201310:58 am

            Oh great! I hadn’t noticed that “Core 2 Extreme”processor series, I thought those were the same as the Core 2 Quads. Thanks for the info, I am pretty sure it will be fine then. It will all come down to how steady my hands are while making those modifications.

            I don’t understand what people use these processors for, or why they would want to replace them and resell them for such a small fraction of their original price. The Intel Core processors, were initially cheaper and are still being sold much more expensive than these Xeon processors. Is it simply an issue of supply and demand or is it also that these Xeon processors are probably very close to the end of their “life expectancy”?

        • syn December 17, 201311:16 am

          It’s probably just supply and demand. Xeons were used in workstations at businesses and for servers, and I guess a lot of businesses are upgrading their systems due to Windows XP support ending in 2014.

          The companies that were the target for these types of processors probably aren’t buying them anymore, so there’s a lot more supply than demand.

          As more people find out about this mod, the prices on the Xeons will probably go up, but since this mod is geared toward enthusiasts, I’m sure the Xeons will always be a decent amount cheaper.

  • john December 20, 201311:17 am

    hi is it possible to build a computer from scratch like this considering you cant update the bios before powering it on.

    • syn December 20, 201311:34 am

      Hi, yes, you could, but you’d need to be careful.

      You’d either have to buy a motherboard that supports the Q9650 with its initial bios or buy from a seller that tells you the current bios version, so you can verify it’s compatible with the processors you want.

  • lu January 2, 201411:10 am

    I have a motherboard Intel Skulltrail D5400XS, is can increase the multiplier of the CPU Xeon X5460? Let me know. Thanks and regards

    • syn January 2, 20141:14 pm

      The X5460 doesn’t allow you to change its multiplier directly (like an extreme CPU does), but you can overclock it if your motherboard supports increasing the FSB.

  • octabrain February 28, 20144:10 am

    Installed Xeon E5440 on Gigabyte P35-ES2L, works fine.

    There is one problem. FreeBSD works well, but SuSE Linux doesn’t. It looks for CPU #1.

    I’ll try Windows Vista.

  • Mark Owens February 28, 201410:27 pm

    I believe I have great news for Dell Optiplex 755 owners. Just yesterday I installed a Xeon X3363 CPU and my 755’s BIOS version A21 recognized the X3363 right off the bat. However, I found it a bit odd that as the operating system (Windows XP SP-3) started to load–a blue screen appeared and stopped the OS from loading. So I then decided to reinstall the Windows XP OS and now this computer boots to BIOS, loads the XP OS and functions as if it was made to run on Xeon CPUs.

    Perhaps someone may know why the OS failed to load necessitating the need to reinstall the OS–for I never had to do this when I installed Xeon E5440 CPUs in my Optiplex 330 and 360 rigs. Hopefully anyone who desires to attempt this swap has the OS start up disk if an OS reinstall is necessary to complete this install.

    This just proves that the person who discovered that Qxx series chipsets–in this case the Optiplex 755’s Q35 Express Chipset (ICH9DO)–does support 3xxx series Xeon CPUs because of their uni-processor configuration–since I mistakenly assumed that the 755’s motherboard had dual-processor support–which it clearly doesn’t. So major props to whoever discovered what many, including myself, overlooked. I tried installing Xeon E5450 and E5440 CPUs in my 755 but to no avail. A major bummer I thought, up until just yesterday since I own 5 Optiplex 755s. Now I am eagerly looking forward to installing Xeon X3363 CPUs in all of my 755 rigs.

    • Mark Owens February 28, 201410:42 pm

      In case anyone is interested, here’s the CPU-Z validation for my Dell Optiplex 755 Xeon X3363 install: http://valid.canardpc.com/dxczhe

      Note that the CPU-Z ID “Name” box states “E5440” yet make no mistake that the 755 will not recognize 5xxx series processors in my experience. If you look down to the “Specification” box it more specifically reads “Xeon X3363”.

      Also notice that the CPU is running a bit hot since my 755 has stock cooling and I submitted the validation when the CPU was under load. I plan on fitting an aftermarket cooler and using Shin Etsu thermal compound to keep the temp down.

      • Walerkz September 4, 20147:12 am

        it says my x3323 is E5420 max temperature i 50 Celsius use stock cooling.Before i had E6550 core 2 duo max temperature was about 35-40 celsius so isnt too bad now

    • syn March 1, 20142:17 am

      Thanks for the update, Mark. That basically confirms what I expected about the Qxx series. I’ll add this to the compatibility section.

      • Mark Owens March 1, 20146:46 am

        I should be the one thanking you since I feel a sort of moral imperative to express my gratitude for your insight–for all I did was reconfirm what you already knew in theory–I just needed to put that knowledge you have shared with us into practice. I tried googling the topic of whether it’s even possible to install an LGA 771 Xeon in an Optiplex 755 and came up empty handed every single time. Without your guidance I would have given up trying to find a Xeon CPU that’s compatible with my 755–and would have had to settle for much more costly Core 2 Quads. Again, sincerest thanks.

    • Mark Owens March 6, 20146:35 pm

      I just remembered that I cleared the CMOS prior to installing the Xeon X3363 CPU into my Dell Optiplex 755–so perhaps this was what caused my computer not to load the OS and the resultant blue screen.

      On my next X3363 install, I’ll try installing the CPU without clearing the CMOS to see if I still get a blue screen.

      • Mark Owens March 13, 201411:40 pm

        I recently installed 2 morel Xeon X3363 CPUs in 2 additional Optiplex 755s without clearing the CMOS and both booted to BIOS and operating system perfectly without a blue screen–so I’m guessing that clearing the CMOS without making the proper BIOS adjustments was probably the culprit.

        I now have 3 Optiplex 755s running on X3363s!!!

        • syn March 14, 201410:51 pm

          Yeah, the blue screens probably had to do with the SATA hard drive setting in the bios. If that’s changed from what it was when windows was installed, your system won’t boot.

    • Walerkz August 17, 201410:03 am

      Hi followed compability list and succesfull installed xeon x3323 in my dell 755 bios version a22 runs great win 7 64 bit http://valid.x86.fr/w6iduu

  • Mark Owens March 2, 20148:27 am

    For those who plan on installing a Xeon E5440 CPU in an Optiplex 330/360–I would suggest that if possible, you use a SLANS version of the E5440 instead of the SLBBJ version. From personal experience, when I installed the SLANS version E5440 CPUs in an Optiplex 330/360, these computers booted up and ran normally.

    However, recently I’ve tried installing SLBBJ versions of the E5440 and my Optiplex 330 and 360 and both showed this warning message at startup: “System does not support the installed processor.” While pressing the F1 key as instructed to do to continue will allow for the operating system to load and the computer to function–in the case of the 330, its CPU fan runs constantly at full blast, although I believe this has nothing to do with the CPU overheating since the core temps for all four cores register in the low to mid twenties Celcius at idle. I’m guessing that this probably has something to do with the difference in S-Spec numbers or Core Stepping of the SLANS and SLBBJ versions of the Xeon E5440.

    • syn March 3, 201412:15 am

      Yeah, it sounds like the E0 stepping microcodes are missing from the bios. A bios mod will probably fix this problem, but most of the tutorials are based around AMI and Award bioses.

      Thanks for the heads up. I’ll mention this for both of those systems.

      • Mark Owens March 3, 201411:15 pm

        Agreed. A kind, generous and ingenious fellow from overclock.net said that he was willing to guide me through the entire process of modding the Optiplex 330’s BIOS and assist me step-by-step in adding the right microcode. However I told him that it would be much easier for me to opt for a SLANS E5440 than attempt to install a SLBBJ E5440 which appears to require a BIOS mod–for I have very limited programming experience especially when it comes to extracting, inserting and removing microcodes. I’d much rather swap CPUs, motherboards, or any other hardware out of the 330 rather than tinker with the CBROM. Heck–I’d rather even unsolder the BIOS chip and solder another one in if that was what it took.

  • Sash March 6, 20142:23 pm

    Olala, got also an offer for an E5450. The E CPUs have the Advantage in the lower max Temperature. Is this right? So in case of OC an E CPU will this be better than a X CPU?

    • syn March 7, 20145:02 pm

      The E5xxx series processors will probably require less voltage and have lower temps for the same speed, so they may overclock better, but it all depends on the individual cpu.

  • ROB March 6, 20143:42 pm

    Hello. I was told by a computer science graduate that you can use a 1600 mhz cpu in a 1333 mhz mother board. He said the cpu just downclocks to 133mhz. What is your opinion?

    • syn March 7, 20144:54 pm

      I’ve heard someone else mention that before, and it sounds like that would probably be true (if the bios had the microcode for that stepping of processor), but I haven’t personally tested this myself, so I’m not sure.

      You probably already know this, but if the fsb downclocked to 1333, it would also slow the processor down because the processor’s speed is a multiple of the FSB speed.

  • Donald Reitzel March 19, 20144:05 pm

    This is the best explanation of CPU and Motherboard compatibility that I have ever seen.

    I have learned the hard way over 10 yrs. of bad experiences about compatibility.

    Thanks for being complete and thorough.

    • syn March 19, 20146:55 pm

      No problem. Glad it helped.


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.