LGA 771 to 775 Adapter – Run Cheap Xeon CPUs in an LGA 775 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 cheap LGA 771 Xeon CPUs into an LGA 775 motherboard.

Table of Contents

• Why would you want to do this?
• Where can I buy an adapter?
• How does the adapter work?
• Minor modification to the LGA 775 socket is also required
• Motherboard Compatibility
• Cheap LGA 771 Xeon Processors
• Installation Instructions

Why would you want to do this?

Xeons are usually MUCH cheaper

The Xeon processors we’ll be talking about are identical internally to most of the high-end Core 2 Quad CPUs. However, they generally cost much less, so this can end up saving you a lot of money. For example, the Xeon E5440 is equivalent to a 3.0 GHz Q9550 (Core 2 Quad), and the E5440 currently runs for about $30 on eBay (about $70 less than the Q9550).

Xeons also typically overclock better

Additionally, if you’re interested in overclocking (making the cpu go faster than its default), Xeon processors are usually binned better than normal processors (especially the lower voltage Xeons), so you can typically achieve higher overclocks with them.

Where can I buy an adapter?

You can find them here on eBay.

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 modifies some of the pins to make it compatible with a Core 2 Quad motherboard.

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.

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 removed before you can install an LGA 771 cpu.

This can easily be done with a utility knife or box cutter, and it isn’t harmful to the socket. With the tabs removed, the socket will then support either LGA 771 or 775 processors (you can still reinstall your old processor if you ever need to).

Motherboard Compatibility

Important: Always update your bios to the latest version before installing a Xeon cpu.

Most of the LGA 771 Xeon processors are identical internally to the regular LGA 775 CPUs (some differ only in clock speed). That’s why this mod is able to work so easily.

Compatible LGA 771 Xeon CPUs

The table shown above is pretty self explanatory. For example, if your system can run the Q9650, you can run the Harpertown (with a 1333 FSB) and Yorkfield-CL Xeons. For more details on the exact Xeon model numbers, please click the links in the table.

The Q9650 has a 1333 FSB, and the Q6700 has a 1066 FSB, so you should only get Xeons with those FSB speeds (or lower) — unless you’ve verified your motherboard supports higher FSB speeds. This is important because some of the Xeons have a higher FSB speed than the similar LGA 775 ones.

If you’re unsure if your bios supports one of these processors, please read the following article: How to Check if Your Motherboard Supports a Specific Processor.

Note for low power (65W and below) systems: If you’re running a low power system (that only supports up to 65W) and your system supports the Q9550S, this mod will also work with the low wattage Xeons (like the L5420).

Cheap LGA 771 Xeon Processors

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

The best deals on LGA 771 Xeons are shown in the tables below. These prices are current as of 11/25/2013.

Cheap 45nm Harpertown Xeons

These are compatible with systems that support the Q9650.

Cheap 65nm Clovertown Xeons

The 1066 FSB processors shown below are definitely compatible with systems that support the Q6700. However, you can also run the 1333 FSB Xeons if your motherboard supports that FSB speed.

I only listed the Xeon processors that are decently fast (over 2.4 GHz) and are relatively cheap right now. For a full list of all the compatible Xeon processors, please see the Xeon CPU list from the previous section.

And although I didn’t list them here, you may also be able to find some good deals on the 1600 FSB Xeons. Just make sure your motherboard supports that FSB before buying them.

Installation Instructions

Things you’ll need

• LGA 771 to 775 adapter
• Compatible LGA 775 motherboard
• LGA 771 Xeon processor that is compatible with your motherboard
• Sharp utility knife, box cutter, or razor scraper
• Tweezers (optional)

Step 1 – Install the latest BIOS and verify it’s compatible with your Xeon cpu

BIOS updates often add support for new processors, so you have the best chance of this working with the latest bios for your motherboard.

If you haven’t done this already, you should also verify that your bios is compatible with the Xeon processor you want to install. If it isn’t, your system will likely fail to boot.

Step 2 – Reset your bios to its default settings

This is necessary because some people have noticed their cpu not running at full speed until they reset their bios.

If you’re unsure how to reset your bios, check out the previous link.

Step 3 – Modify the LGA 775 socket to support LGA 771 CPUs

LGA 775 Socket Plastic Tabs

In order to physically fit the Xeon processor into the socket, you first need to cut off the 2 plastic tabs shown in the picture above.

The tabs are only there to stop you from installing an incompatible processor. Removing them won’t hurt anything (you can still reinstall your old LGA 775 cpu if you ever need to).

Caution: Be careful to not bend any of the pins in the socket, and make sure that you fully cut off both of the tabs. If they’re not fully cut off, the processor may not seat correctly.

The tabs should come off fairly easily, and tweezers work well for removing the plastic from the socket once it’s cut off.

With the tabs removed, the socket will then support LGA 771 or 775 processors.

Step 4 – Install the LGA 771 to 775 adapter

First, wash your hands thoroughly and dry with a paper towel

This is necessary in case your fingers come in contact with the adhesive of the adapter. Clean hands are less likely the weaken the adhesive.

Remove the cover from the adhesive

All recent adapters come with adhesive preapplied to the bottom of both ends of the adapter, which will help it stick to the processor.

If yours does, peel off the protective cover to reveal the adhesive.

If your adapter doesn’t come with adhesive or it isn’t sticking very well, you can also use double-sided tape to secure it to the CPU. Just apply the tape to both ends and cut off any excess. Make sure the tape won’t cover any of the pins on the processor.

Line up the adapter on the bottom of the Xeon cpu

LGA 771 to 775 Adapter

Static electricity warning: The circuits on the processor (above where the adapter goes) are sensitive to static electricity, so touch a screw on the back of your computer to discharge yourself before handling it. If you’re using metal tweezers, it would also be a good idea to discharge them as well.

Carefully lay the adapter onto the processor and align it as shown in the picture above. Tweezers are helpful here.

Make sure the arrow on the bottom of the adapter is pointing toward the triangle on the cpu. Some adapters also have a triangle on the adapter instead of an arrow.

When you’re confident the adapter is lined up right, press down on both ends of the adapter to secure it to the processor.

Now double check that the adapter is still lined up correctly and is tightly connected to the processor. You don’t want the adapter moving when you install it into the socket.

Step 5 – Install the CPU into the socket

Place the cpu in the socket

Make sure the triangle on the processor is lined up with the socket as shown in the picture.

Ensure that the processor is fully seated in the socket before closing the lid. If the plastic tabs were not cut off fully, it may not seat correctly.

Step 6 – Finishing up

Before booting up for the first time, please reset your bios if you didn’t do it earlier.

When you start the system for the first time, it may cut itself on and off a few times before booting up correctly. This is normal with some systems, and it should start normally in the future.

That’s pretty much it as far as the mod goes, and as mentioned earlier, if you don’t have an adapter yet, you can get one from here.

Questions, comments, or feedback?

If you have any questions, comments, or feedback please leave a comment below.