[Jeremy Allen] “does that mean I can’t use a 667MHz stick, or will it just be a bit slower?”
you can use the older 667mhz ram in a new macpro, but it will lower the whole bus to 667mhz, so any 800mhz ram you have will operate at 667mhz too…
also note that you should add ram to each riser that the matches the size of the ram in the respective slot on the other riser…. did that make sense..??
here are your slots and risers:
riser a: slot 1
riser a: slot 2
riser a: slot 3
riser a: slot 4
riser b: slot 1
riser b: slot 2
riser b: slot 3
riser b: slot 4
the ram sticks in a1 & a2 (or a3 & a4, or b1 & b2, etc.) need to be matched pairs (they will need to denote this when purchasing). but if you add ram to your mac, to get the best performance, you want to add the same size ram sticks to b1 & b2.
so if the system came with 2x1gb sticks in a1 & a2 you would want to add 2x1gb sticks to b1 & b2 to get the performance benefits of interleaving. now say you want to get more ram and bigger sticks but don’t want to toss your original ram. you could add 4x2gb sticks to a1, a2, b1 and b2, then bump your original 2x1gb sticks to slots a3 & a4.
if you really wanted to get the best performance from your mac, filling all slots is advisable (you can check out benchmarks at barefeats.com), but there is nothing wrong with installing in smaller increments as long as you keep the above upgrading system in mind.
KCPQ, KMYQ & KRCW