Gorf runs like ass...no matter what processor you have. It runs as crappy on my Opteron 165 as it does on my XP2100+. It is just a really crappy running game. For some reason I don't remember Gorf having these speed issues...but I've read somewhere that they, it, in fact, did?!
The only verticals that really slow my machine down are the newer HIGH VOLUME shooters where there is a ton of stuff on-screen all blowing up or shooting, or what not...and even then, I experience a minor slow down and then it's all good...
That is on an XP2100+ (overclocked to 2.0ghz).