So I just bought my first Mac (an iMac with Ati 4850) and coming from the PC side I'm obviously a bit of a RAM whore in the sense that I'm always checking my available ram since I like to run a lot of things simultaneously and I'll also close things down that are a bit unnecessary if it's eating up a decent portion. Something I'm trying to figure out about the Mac is that it seems to handle RAM a bit different. Here's my situation (or what I've noticed at least): Lets say you turn on the iMac. From the start you have rougly 3.3-3.5gb of the 4gb available. I decide to do a little Photoshop work and listen to some music via iTunes and I've also got Adium and a Safari or FireFox open. On average, I notice this drops me down to about 1.8gb of ram (still a good amount) with Photoshop taking up the biggest chunk. Now, on Windows if you quit/shut down Photoshop, your memory was pretty much restored. However, on the Mac that doesn't seem to be the case - at least not in full. Say Adobe is eating 1gb (figuratively) and I shut it down. It will only restore a quarter of that to my available system ram. At first, I assumed the mac was sort of caching memory for applications that I've originally opened so that if I decided to open that app again it wouldn't use another 1gb since the 1gb was all ready being cached. However, that also isn't the complete case. If I re-open Photoshop later it doesn't use another 1gb, but still seems to be using an additional 25-50% of the original 1gb that it took when opening it the first time. Over the course of a day I sort of that I get incredibly close to that zero ram because I've been opening/closing applications and each time it takes a little more ram. From what I figure, it seems to be best to just leave an application always open once you open it on a Mac because you're not going to get your full ram back regardless. Is this common or is there something else I need to be doing?