I run all my cards at 300mhz memory. If I go lower it affects my hashrate and stability.
I discovered this recently - was trying to OC to 950 on a 5870 at 150 memory, and the machine kept freezing, even though the temps were fine etc. When I put the memory back to 300, it got nice and stable again.
aye, I agree on the memory thing. it is possible to go too low. On
my 5830's clocked at 1020GPU they seem most stable at ~345 mem. This seems to vary a bit based on which card models, mem bandwidth, gpu OC and the work size being used.
It's been a while since I was testing any of that but it seemed to somewhat coincide with what the total memory % being used on the cards were. I.e., at too low mem Mhz the memory usage would get up clost to 50% and the issue seemed to start at about that point. Though, other than just casual observation of it I've no way to know if it was the actual cause or not.
cheers
TL;DR start at ~600mem and work your way down 50 at a time until you find it unstable. Then bump it back up by 10 or so at a time until you find your sweet spot.