Q: I have an older Apple PowerMac G5, the dual 2GHz model. I want to install more RAM, but I can't remember the order that chips should be put in the slots - and I can't find the computer's user guide. Can you help?

A: PowerMac G5 computers have either four or eight RAM slots, supporting up to 4, 8, or 16GB of total memory, depending on the model. The slots are arranged into two banks of two or four slots. DIMM sticks should be installed in matched pairs, with one stick going into each bank, working outward from the inner-most (lowest numbered) slots in each bank. The slots are arranged as in this diagram...

slot 4

slot 3

slot 2

slot 1

slot 1

slot 2

slot 3

slot 4

...and a pair of RAM chips should be installed in slots 1 of each bank first, then slots 2, then slots 3, and finally, slots 4 should be filled.

Be sure you get the correct type of RAM chips; which DIMMs will work depends on your particular computer. Some models support DIMMs up to 1GB in size, others support up to 2GB chips, and the last-generation G5s supported up to 4GB chips. Some require 184-pin, 400MHz PC3200 chips, while others need 240-pin, 533MHz PC4200 DDR2 chips.

PDF manuals for all the PowerMac G5 models can be downloaded from the Apple Support site. Technical specifications are also available at the site.