How do you upgrade the RAM in the original Mac Pro? How much RAM of what type does it support?

Please note that all systems mentioned in this Q&A have been discontinued. The original Mac Pro models were replaced on January 8, 2008 by the "Early 2008" Mac Pro models.

Installing RAM in the original Mac Pro is easy, but it is important to be sure that you purchase the exact memory needed by the system for optimum performance.

In basic terms, the original Mac Pro requires "667 MHz DDR2 ECC fully-buffered DIMM (FB-DIMM) memory", but more precisely, the memory must meet these specifications:

• 667 MHz, FB-DIMMs
• 72-bit wide, 240-pin modules
• 36 devices maximum per DIMM
• Error-correcting code (ECC)

Each FB-DIMM has its own chip called an "Advanced Memory Buffer" (AMB) and "heatsinks on either side". Some less expensive versions of FB-DIMM memory do not have heatsinks that meet Apple's minimum standards for use in the Mac Pro. According to Apple, the "Clovertown Eight Core" Mac Pro is even more strict regarding memory standards.

Apple also reports that "DIMMs must be installed in pairs of equal size from the same vendor". There are eight FB-DIMM slots in total on two "riser cards" (four slots per card) that can offically hold 16 GB of RAM. However, third-parties, such as site sponsor Other World Computing have been able to expand the memory in the original Mac Pro models to 32 GB using eight 4 GB modules.

As is printed on the inside of the door of the Mac Pro, FB-DIMMs must be installed in a particular order as well. The default configuration shipped with a pair of 512 MB FB-DIMMs installed in the first and second slots (towards the "gold fingers" in the top riser card), which leaves six slots free. The next pair of FB-DIMMs must be installed in the first and second slots of the bottom riser card, the next pair in the remaining slots of the top riser card (slots three and four), and finally the last pair in the last two slots (three and four) of the bottom riser card.

The quick installation instructions are:

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 1 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.

Photo Credit: Site sponsor PowerMax. PowerMax also provides a number of other photos that you may find helpful when upgrading the memory or other internal components.

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.

Should you choose to purchase memory for your Mac Pro from a supplier other than Apple to save money, the always excellent XLR8YourMac has posted a page of "Mac Pro Owner Reports on Third-Party FB-DIMMs" that you also may find to be helpful.

To purchase quality memory that is guaranteed to work with the Mac Pro models, please visit site sponsor Other World Computing.