that's something I've been wallowing in for a while now... can't seem to really get to understand it fully - what's the big difference between 2k and 4k refresh rate memory modules in regard of performance in a 68k Macintosh? I'd like to upgrade the memory in my mac and I've read about those two types of mem but don't really seem to get which one's superior, if at all. Is there actually a noticeable difference between those modules or does it not really play a huge role in an, well, "aged" mac? Which one would be good on an LC575? Hope there's someone that could help me out with that, cheers!