How do you upgrade the RAM in the "Early 2008" (Harpertown/Penryn) Mac Pro? How much RAM of what type does it support? Is it backwards compatible with RAM from the original Mac Pro?

Just like the original Mac Pro, installing RAM in the "Early 2008" Mac Pro is easy, but it is important that the memory meet exacting standards to function as intended.

Officially, the "Early 2008" Mac Pro requires "800MHz DDR2 ECC fully buffered DIMM (FB-DIMM) memory", but more precisely, the memory must meet these specifications:

• 800 MHz, DDR2, FB-DIMMs
• 72-bit wide, 240-pin modules
• 36 memory ICs maximum per DIMM
• Error-correcting code (ECC)

However, the always excellent BareFeats also discovered that the "Early 2008" Mac Pro is capable of using 667 MHz FB-DIMMs that are compatible with the original Mac Pro, albeit at a "maximum penalty of 4% in speed".

Apple also reports that "DIMMs must be installed in matched pairs". There are eight FB-DIMM slots in total on two "riser cards" (four slots per card) that can hold 32 GB of RAM.

Detailed information is printed on the inside of the door of the Mac Pro, but these general instructions may be useful as well:

1. Backup all data on the Mac Pro and verify that the backup is successful.

2. Shut down the Mac Pro, unplug it, and disconnect any cords or cables.

3. Although it is probably most intuitive to just open the computer and pull the memory riser cards out the side, Apple recommends that service technicians "open the computer, and lay it on its side with the access side facing up".

4. Be sure to "wait [at least] 5-10 minutes for the computer to cool down".

5. Discharge static electricity by touching a metal surface (or better yet, use a grounding wrist strap).

6. Hold a riser card by the "two finger holes" (on the corners), "pull it out of the memory cage and place the card DIMM side up on a soft, clean cloth." Remember that if you are installing an additional 2 GB of memory, you will need to install the FB-DIMMs in the bottom riser card, but you may find it easier to remove the top riser card first and then the bottom one.

7. With the memory riser card(s) on a flat, stable surface, install the FB-DIMMs in the FB-DIMM slots.

8. Confirm that the memory is seated properly in the riser cards, and in turn, reinstall the memory riser cards in the Mac Pro.

To purchase quality memory that is guaranteed to work with the "Early 2008" Mac Pro, please visit site sponsor Other World Computing. OWC also provides helpful videos that cover the memory installation process.