I see. Then maybe it's something specifically related to the quake 2 code? You could try looking for other Q2-based games (such as Warsow) and see if they do the same.
I'm having this same problem we are discussing in a thread above.
The variable is the equipment. The less equipment the better. Any more than three rows of equipment and it gets super laggy.
Then when you go to a map, you bring items/equipment. When adding those items/equipment to the items already on that map, you reach a certain number where framerates plummet.
I have Invidia Go Force 7700, using fresh driver from Asus web site. 2 gigs ram, dual core. Nothing else lags it.
MY BAD: Research shows that turning off dual core function with this game fixes this problem. alt-taB OUT, contr/alt/del, right-click on process, set affinity, uncheck one core, either one. Fixed. Must be a multithread problem with doom2 game engine.