Several Counter-Strike server administrators have reported seeing higher CPU
usage on their servers after updating to the latest version of
Counter-Strike (1.3). This increase in CPU usage is related to the fix for
the hitbox problems experienced in earlier versions of Counter-Strike.
The blending the server must do to accurately reflect each player's position
and hitboxes has been reworked to be more accurate than it was in previous
versions. The trade-off for more accurate hitboxes is that the server must
do more work blending the models, hence the higher CPU usage.
Eric Smith
Valve Software