Brian Hook van id Software heeft z'n .plan geupdate met wat info over QIII server stuff:
Two common questions I'm getting are "How much net bandwidth do I need for a server, per player?" and "How important is floating point performance for a server?"
General rule of thumb for now is that you need about 2-3K/sec of bandwidth per player for a server.
Floating point performance is still very important for a server. A safe assumption is that a Cyrix or K5 CPU will be able to support only about half the players of a comparable Intel CPU. K6 isn't nearly as bad as the K5 and Cyrix, however it's not as good as an Intel for regular floating point stuff, so figure (VERY rough) about 75% of an Intel processor. Obviously a LOT of this depends on the complexity of the underlying maps.
So, just pulling numbers out of thin air, you could say:
Intel PIII/500 - 40-50 players
Intel PII/300 - 25-30 players
AMD K6/300 - 18-23 players
Cyrix MII-300 - 12-15 players
While we do plan on supporting 3DNow, etc. we can't promise it out of the box just yet.