well, i have 2GB CL2 DDR RAM in my linux workstation running native 64bit gentoo
due to memory failure i had to run the box at times with both 512MB and 1GB
512 is far from usable, 1GB was way slower.
This might be because what linux does is taking all the memory it can get and use it as buffer for low speed IO operations.
so my whole memory is used up after using the box for an hour or two.
and since i'm using gentoo, i bought that computer with exactly this in mind.
dualcore x2 4400+ with 2gb ram and a raid mirrored pair of sata raptors
if it comes down to compiling, this box is awesome
ram alone wont help you in all cases, you have to match the other hardware too