I may have asked that wrong, so here's what I mean. I have a mid-2010 iMac that came with 4GB of memory -- two 2GB chips. After doing a scan using Crucial's scanner, I found out that this thing has FOUR slots for RAM, not two as I thought. Each slot can hold up to a 4GB chip. So my thought was instead of my previous plan of upgrading to 8GB for $45, I could leave the other two in and have 12GB. But I know in the past, mostly back in my PC days, that computers would sometimes really get pissed at you if you mixed memory chips like that. I'm less inclined to think that since it would be pairs and Macs seem to be infinitely smarter at this than PCs, but I just don't know. So I would appreciate some advice on this. I've got some stuff I run that creates a "Web Process" that eats up memory like Pac-Man eats dots. Thanks!