unfortunately it is a 512 x 72 , and compatible ram has to be 256x8. I am not a memory expert either, but i have contacted several people who are (tech support at memory suppliers) and they say it is pretty much limited to one part, which is discontinued. Unigen is going to supply areca with the neccesary chips, but there is a bit of a wait for them to get to market (eta:unknown). I will just live with the 2gb, even though there are tons of 667mhz chips which would work i just really insist upon 800mhz! I am semi-content to wait...