Hi all, I have a question about something that is puzzling me with my system, and I wonder if any of you can help me with it. I have searched out and read a number of older threads but they didn't really help me (I did try though). Also, sorry to be so wordy, but I can't see holding back information and then we just have to go back and forth while you pry it out of me bit by bit This is my 4-month old MBP 13", with 2.4ghz C2D, 4GB RAM, and 250gb HD. I'm running 10.6.4. I'm a pretty light user EXCEPT I'm a major "tab hog" in Firefox I just love tabs! So, I notice that as I build up my tabs, my "Memory pie" starts to look a bit odd. I'll have almost no free RAM (say 30mb), about 2GB of active RAM, and then over 1 GB of "inactive RAM." But when the free RAM gets down that low, FF gets really unresponsive and starts beachballing. From my reading, it seemed that the system would "know" to just make use of that "inactive" RAM if it needed it, but this almost makes it seem like it's not doing that. Another thing is that, for example, right now I have 2.8 GB of Page Ins, but relatively whopping almost 7 GB of Page Outs. Again, from my reading it sounds like having a lot more page outs than page ins means you need more RAM. But that seems odd with 25% of my total RAM "inactive." Here is a shot of my Activity Monitor now; this is the behavior I mean: FF is using around 40-50% of my CPU, and everything else is at like .8% or less, so although FF is using a lot, everything else is nearly nothing. Also, I use FlashBlocker on FF, so even though I have a lot of tabs open, there is not rampant flash usage on them. Okay, now I also read that "inactive" RAM comes from programs you recently closed, in case you open them again. Okay, that makes sense. Except, to experiment, after I read about that, I closed all my programs except FF and Mail for a long time, and still I had the extremely small amount of free RAM, and the huge amount of inactive RAM, at which point FF would start to beachball. At the same time the computer begins to get much hotter. Not that it's too hot, but just this seems to go along with the overall behavior. It will go from its usual 45ºC up to 60ºC or so. Again, not a worry in and of itself, but it coincides with the "no" free RAM and the beachballing FF. If anyone can shed any light on this, I would much appreciate it. I did read Apple's page on memory and how it works, but they were a bit vague on a few things. Thank you! Miss Terri PS: I do have 8GB of RAM ready to install, but I still want to understand this, because.... am I then going to have the same thing but just with MORE inactive RAM? I want to understand it.