This one is a little weird. I've been searching for answers for a while but haven't had any luck. I have a MacBook Pro with 8GB of RAM and Snow Leopard. I've noticed that applications get slow when they surpass 1GB of RAM usage, regardless of how much total RAM is available. I notice it most frequently with Firefox. Everything is fast, then suddenly a page will stutter when I scroll. I'll look at the "Real Mem" in the Activity Monitor, and it'll be within a few MB of 1GB. I'm convinced this is not entirely a Firefox thing, though, but it's most noticeable there. I see it with VirtualBox as well and various Java processes that have more than 1GB allocated to the JVM. Oddly, it causes a CPU spike, not a disk usage spike as I'd expect with virtual memory churn. Thoughts? Is there some memory parameter I can set? Has anyone else seen this?