I've noticed that Xcode 3 by default runs as a 32 bit app in Leopard, so I switched that option off and started it as a 64 bit app. Then I opened Activity Monitor to see if it would tell me that it's in 64 bit mode (which it did). While doing this, I noticed that Xcode used (or reserved) about 35GB of virtual memory (yes, gigabytes). So I put it back in 32 bit mode, and it only used 1GB of virtual memory. Not that I care much about this difference in practice, but I do wonder why there would be this big a difference between the two. Does anyone have any idea about this?