1. You could run the server on Windows 2008, with "srcdsfpsboost.exe" running in the background, and enable HPET under the "advanced options" section of the "Server control" page in your control panel. This is the easiest solution.
2. You could run the server on our Gentoo Linux install, using the kernel we provide. (The CentOS install's kernel won't work as well.) To achieve a stable 950 to 1000fps, start your HL1 server with a command line that looks like this:
chrt -r 20 ./hlds_run -game xxxxx +ip xxx.xxx.xxx.xxx +maxplayers xx -pingboost 2
Or your Source/Orangebox server with a command line like this:
chrt -r 20 ./srcds_run -game xxxxx -ip xxx.xxx.xxx.xxx +maxplayers xx
The "chrt" bit of this tells the kernel to run the process as "real-time", and removes the slack on its timers, allowing for a higher sustained FPS (the numerical RT priority that you use does not make a noticeable difference here).
Whichever method you use, make sure to check the FPS remotely with "rcon stats", rather than typing it directly into the server's console. Typed directly there, "stats" gives erroneous output.
Additionally, make sure that your "server.cfg" file specifies:
- A sys_ticrate of 0 (unlimited) or 2000+, for HL1-based games
- A fps_max of 0 (unlimited) or or 2000+, if you're running a Source or Orangebox-based game