This guide is intended for both buyers and sellers of used motherboards in the hope of making these transactions more satisfying to both parties.  It is written from the perspective of a Computer Science Ph.D. who has been a denizen of the Internet since 1978, and is based upon his experience selling hundreds of used motherboards and systems.

While this guide is for used motherboards, much of its content is applicable to new boards as well.

Untested Boards, Working Pulls and Tested Boards 

When buying a used board, you need to consider the condition of the board and of course the normal buying concerns such as the seller's return policy and feedback rating.  Sellers often state that a board is untested, a pull from a working system or tested.

We consider all boards to be used unless they are still sealed in their original packaging.  Open box does not necessarily mean new and unused.

Untested Boards

An untested board is exactly that and even with a liberal return policy, your risk of paying for round trip shipping costs and not having a working board is going to be higher than with a working pull or a tested board.  When a seller offers a DOA warranty, but does not state that the board has been tested, in all likelihood it hasn't been.

From a seller's perspective, a board that is going to sell for just a few dollars may not be worth the time it takes to test it.  Some sellers may not be equipped to test even when they are selling relatively expensive boards.

Working Pulls

When a board is described as a working pull, the question arises of how the seller knows that the machine the board was pulled from worked?  If  the seller owned and used the machine from which the board was pulled, then the statement that the pull is from a working machine may hold considerable weight.

In the end, it probably isn't worth worrying too much about this.  If a seller says a board is a working pull and has a good feedback rating, then the board is most likely a working pull.  Providing  misleading descriptions of items for sale is like fast speeding and aggressive driving.  You won't get caught every time, but you will get a few tickets.

Tested Boards

When a board is sold as tested, the question is how was it tested?  Does the seller specify what they mean by 'tested'?  What does 'fully tested' mean?  We have no idea what the answer to this last question is.  As with working pulls, a seller's feedback may be more important than the question of exactly how the board was tested.

In our experience, the fans spin on a majority of bad motherboards.  Simply powering up a motherboard  tells you little more than that the power supply is turned on.

Post Testing

Post testing essentially tests the machine to just before the point of booting to the operating system.  Post testing can be done with a known good power supply, CPU, single stick of memory and  video card if the board does not have onboard video.

In our experience, post testing will catch many bad boards, though it is possible for a board that post tests to have other problems.

Built-Out Testing

Another form of  testing that may catch some bad boards that post testing does not is to build-out the board into a functioning computer on the bench.  All that this takes beyond post testing, equipment wise, is to attach a hard drive with an OS installed.

Once this is done and the board boots, it is relatively easy to test the USB and LAN ports.  Window's device manager can be checked to make sure that all of the motherboard's components, such as onboard audio, are recognized by the device manager.

No testing methodology catches every possible problem, which is why it is important to check the seller's return policy.

How do the Capacitors Look?

This applies mostly to older motherboards that were not made with premium capacitors.  Capacitors that are bulging and/or leaking may eventually lead to board failure.

Which CPU's Will Work with the Board?

If a CPU fits into a board's socket that does not mean that it will run.  Some board manufacturers keep their CPU support lists up to date.  Some do not update  them and hide the information about new CPU support in the bios update notes.  Some manufacturers do not maintain CPU support lists.

This is one of the reasons sellers cannot guarantee component compatibility when they sell motherboards.  It is worthwhile visiting the board manufacturer's web site, checking to see if there is a CPU compatibility chart, and perusing the bios update notes (if there are any).  Downloading the board's manual and giving it a read is also a good idea.

CPU Flavors

The most difficult part of CPU compatibility is often the confusing support for different versions of a CPU. Not all LGA775 Intel CPU's will run in all LGA775 boards.  For example, a board that supports dual-core LGA775 CPU's may not support Core 2 Duo (C2D) CPU's.

We recommend that you check the motherboard manufacturer's CPU support list for a motherboard to determine which CPU's the board supports or whether the CPU you have is supported by the board.

Consider Socket 478 P4 CPU's.  The Northwood version is no longer in production (a few are still in retail channels and they are often sold on eBay).  The Prescott version, which runs much hotter and performs no better, succeeded it.  Many used Socket 478 motherboards will not support Prescott processors.

Even if a Prescott runs in a motherboard that does not support it, you can end up slowly frying the power supply mosfets, which were not designed and layed out to handle power hungry Prescott processors.  We are not big fans of the Socket 478 Prescott room heaters and recommend a Northwood be used even in Socket 478 boards that support Prescott processors.

The secret decoder ring to knowing whether a Socket 478 CPU is a Northwood or a Prescott hinges on the amount of L2 cache on the CPU.  Northwoods have 512KB of L2 cache, while Prescotts have 1MB.  On top of the CPU there are three numbers separated by slashes.  The first is the speed of the CPU.  The second is the amount of L2 cache and the third is the front side bus (FSB) speed of the CPU.

Pay Attention to the Front Side Bus Speed

Buyers should check the maximum FSB speed supported by the board and not use a CPU with a faster FSB.  Sometimes a CPU with a faster FSB will work, but will run at reduced speed.  Sometimes, the board will not even post.  There are a few exceptions related to a board's ability to be overclocked.  For example, some Nvidia nForce2 Socket A boards list a maximum FSB of 333MHz, but can successfully overclock the FSB to 400MHz (200X2) in the bios when not using onboard video.

Newer boards allow the FSB to be set from within the bios.  Some will detect the CPU's FSB speed and automatically set it after the first post with a new CPU. 

If a board will not post because the FSB is set too high in the bios, some boards will revert the bios to default settings which will set the FSB to its lowest setting.  If that does not work, resetting the CMOS will set the FSB to the board's lowest speed, which will allow you to enter the bios and set the correct FSB speed.

Some older boards use jumpers to set the FSB speed.  With these boards, the jumpers must be set to match the board's FSB speed to the CPU's.

If you are unsure how the FSB is set on a given board, check the board's manual, which can almost always be downloaded from the board manufacturer's web site.

Uh-Oh, That CPU May Not Work Until You Update the Bios

Another got-ya when it comes to CPU support can be the bios version.  After a board comes out, new versions of the CPU may be introduced that require a bios update.  It is very frustrating to get a motherboard and discover that it will not support your CPU without a bios update.  This is one of those chicken and egg problems where you cannot update the bios using the CPU you have.  Instead, you have to find a CPU that the board will post with and use that CPU to update the bios.  It is only after the update is done that your CPU will work with the motherboard.

As a seller, we try to be aware of the boards for which this can be a problem and update the bios to the latest available version.  When we do update the bios, we make sure to mention it in our listings.

What Memory Will Work?

Many boards are very forgiving of memory and will pretty much work with any memory that meets the board's specifications.  A few boards can be very picky.  Sometime a board will work with one stick of the memory installed, but will not work when the second stick is also installed.

The board manufacturer's memory compatabiltiy list (if they have one) can oftentimes be useless.  The list may contain very few entries.  You may not be able to buy any of the memory listed as the list gets old.

Many memory manufacturers have memory configurators that will tell you what memory will work with a given board.  Some retailers also have configurators, but we prefer the ones provided by memory manufacturers.

There are valid reasons why sellers of used motherboards cannot guarantee memory compatibility.

Which Video Cards Will Work?

If the card fits into the slot, 99% of the time it will work.  With VGA slot cards there is a potential for trouble mating older video cards to newer motherboards.  Very early VGA slot cards used a higher signaling voltage than newer cards do.  There are notches on the video card connector that correspond to these voltages and you would think it is not possible to put a card into a board that will not support it, but it does happen..