I've got a Mac Pro that I use for gaming (Windows) and design (Mac). I've got 4 gigs of RAM in it now, but I'm wondering if the inclusion of another 4 gigs would be a useful addition.
It completely depends on what kind of "design" apps and/or games you run, how many you run.
Does anyone know how well Windows 7 would manage this extra RAM?
Win7 (and Vista) have awesome memory managers, 7 especially. 7 will manage everything for you and adjust according to how you use your machine (this is just one of many reasons why it's so much better than XP). The more you add in the more it'll use it (it's called SuperFetch,
read here to understand more). However, games are only going to need/use so much. Honestly 4 GB is a solid amount.
Would I see a speed boost for loading gamings/booting/multi-tasking?
By adding more RAM on top of your 4 GB? Probably, but nothing insane. The more RAM you add the more you'll be able to do at once though. It's cheap so why not? 8 GB is a good solid amount that you won't find yourself need more of, so I'd go for that amount.
Also, I know I'd have to use the 64bit version would this be problematic running certain games if they aren't optimised for 64bit?
No, not at all. Windows (Vista and 7) have something called WOW64. It let's 32-bit apps/games run natively on it, no emulation involved. I've personally never encountered anything that doesn't run, but apparently they exist. Honestly though, if an app doesn't run it's usually because it's very poorly developed in the first place. You won't have any slow downs. If anything, you'll notice more speed ups.
On the mac side, the work I do isn't very RAM intensive but would in notice a general boost?
OS X loves RAM. More so than Windows. You probably won't notice any difference with already having 4 GBs, but what exactly do you do? Again, RAM is dirt cheap and getting an extra 4 GB (for a total of 8) will definitely future proof yourself. I'd be surprised if you managed to hit that 8 GB ceiling.
