This info came directly off of
Firing Squad. I didn't write it, they did.
"As of right now, there are two methods of benchmarking in Jedi Knight II. One option is to create a shortcut to the multiplayer executable file for Jedi Knight II and add ?+set sv_cheats 1? to the target field of the shortcut. Therefore, the target field would read:
"C:\\Program Files\\LucasArts\\Star Wars JK II Jedi Outcast\\GameData\\jk2mp.exe" +set sv_cheats 1
Next, you drop the console by pressing the shift and tilde keys, and enter ?timedemo 1?, press the return key, and then type ?demo jk2ffa?. Once the timedemo is complete lower the console and press the Page Up key until you see your frame rate.
Another option (officially sanctioned by Raven Software) involves running the multiplayer executable and typing the following in the console:
devmap ffa_bespin
timedemo 1
disconnect
demo jk2ffa
Once the demo is complete scroll up to see your frame rate."