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

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.

Apple provides a PDF version of the instructions as well, which absolutely should be read before installing memory, but perhaps even better, Apple Specialist TDCurran has provided a step-by-step video of the process:

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 for the original Mac Pro.

Site sponsor Other World Computing sells quality memory that is guaranteed to work with the Mac Pro models at affordable prices.