We all know it's a fact that you can't utilize more than 3.2~gb of ram on a windows 32 bit system. We all know that for more than 4GB y ou must have a 64 bit OS. for the longest time I played with 4GB on Vista32 without significant problems.

I would use about 2.6gb of ram out in the world and around 2.9gb in shattrah. Everything was fine and dandy for Team Doublemint, which was setup with the paladin as the leader with medium graphic settings (clip plane being the only one that really affects memory notably) and the other 4 being set very minimal (wall of fog vision).

I switched to playing 5 shaman primarily, using PIP and having setup the configuration to have no specified leader I quickly found that minimal graphics settings were a hindrance. I setup the 5 clients with 50% clip plane, all other settings the same as they were for the paladin. A relatively heavy UI (same as I used for the pally), etc.

Memory usage on Vista32: 2.8gb in the world, 3.2gb in shattrah... in Shattrah I would lag so bad I couldn't successfully traverse town if I tried running all 5 through... 4 was fine.

So I upgraded to Vista 64. Same system, same wow install, same UI, etc...

Now I'm using 3.2gb of ram out in the world, this is higher, and I'd assume this is due to the 32 bit application overhead in a 64 bit OS.
In shattrah I'm using about 3.6gb-3.8gb of ram, with a bit of room to spare the system runs fine. I ran through at prime time last night, it was by far the busiest I'd seen Shattrah in ages, and had no performance issues. I went ahead and bumped the clip plane out to max on all 5 clients, I started paging ram again from the extra overhead... that last 50% really makes wow look better, but since characters/npc models dont load in the last half, it's really just cosmetic.

To be on the safe side I'm upgrading to 8gb of ram, of course the only reason I'm going from 4gb to 8gb is I have 4x1gb sticks right now, and I prefer matched memory so I'm going to bump up to 4x2gb sticks...

All said and done I believe I should be able to run 5x clients with full clip planes once this is done.