Q: 2x of 512 MB, or just 1x 1GB?
A: Hi, If the 512MB chips have the same specifications as the 1GB chip and they do not support dual-channel architecture, then they will run at equal speeds. But, if the 512MB chips DO support dual-channel architecture, then you will see a performance boost over the 1 x 1GB chip. Personally, I believe the best ram setup is 2 x 1GB dual-channel (if your motherboard supports it of course). Cheers!