high benchmark crap CZ performance

2 computers

1st one = amd64 3200+ with a 6800gt = 3700 on 3dmark05 and 99 fps constant in CZ

2nd one = p4 2.8ghz with the same 6800gt = 3800 on 3dmark05 BUT with crap fps on CZ - hovering between 40fps and 80fps

To test things out i threw an x800 and a 9600 into both machines and whilst they benchmarked similarly on each, they performed much better in CZ on the 1st computer than on the 2nd

what is the go? any help appreciated



ps both comps have similar specs, latest drivers, same in game settings etc

 

is it the mobo and cpu on the second pc?

maybe combined with low speed ram?