Server Requirements (Beta)
16 Players: Haven't benchmarked this yet, but we don't expect it will take much CPU to run this
32 Players: CPU usage - 1 Core of a 2.6 GHZ Core I7 or equivalent (i.e. the server process will take most of 1 core, with a few smaller threads on other cores). We also tested on an Intel Core2 Quad Q8400 @ 2.66GHz and that could handle 32 players but I wouldn't try and do 32 players with a machine much slower than that.
64 Players: Goal CPU usage - 1 Core of a Intel Xeon E3-1270 3.4 GHZ (3.8 GHZ actually with Turbo enabled) or equivalent (i.e. the server process will take most of 1 core, with a few smaller threads on other cores).
A note on performance:
64 players was pushing the test machine (Intel Xeon E3-1270 3.4 GHZ (3.8 GHZ actually with Turbo enabled) pretty hard on certain maps, but did handle 64 players. Likewise 32 players pushed the Intel Core2 Quad Q8400 @ 2.66GHz pretty hard at 32 players, but did handle it. We're working on some final optimizations that might get the performance a little better, but there won't be any drastic changes from these specs.
Likewise the number of players the server can handle (i.e. how much performance is needed) varies from map to map, and gametype to game type. Smaller maps and countdown tend to perform better than larger maps in territory or firefight. So if you run smaller maps only on your server, you might be able to push the slots higher. Just watch your CPU usage, and more importantly the ping of players connected. Ping will climb a bit as the server gets under load and as CPU usage goes up, this is to be expected. But watch the ping, if it is a server near you and the ping starts to go above 100ms consistently, then you are likely pushing your server too hard and need to reduce the number of slots.
What I have found is that it looks like an Intel Xeon E31270 @ 3.4 GHZ (3.8 GHZ actually with Turbo enabled) can just handle 64 players now, and is being pushed pretty hard. We've got a last batch of optimizations that we're going to try over the weekend that might bet it down a bit lower so the CPU isn't pushed quite as hard (possibly getting things down by about 5%). We tested on an Intel Core2 Quad Q8400 @ 2.66GHz and that could handle 32 players but I wouldn't try and do 32 players with a machine much slower than that. As mentioned before, the final optimizations might push this down a little, but nothing drastic.