what is the cause of my frame drops in bioshock?

gomilly

Honorable
Oct 1, 2012
315
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10,790
playing bioshock infinite recently at low settings and i get these big frame drops down to 35 or 45 and its worse than it sounds because i get terrible stuttering when it does this too.
i monitored my hardware usage with task manager and gpu-z during gameplay and during these spikes my cpu spikes to sbout 90% max.
my ram usage doesnt move the whole time im playing it stays below 55% and my gpu doesnt go over 70%.
my pc specs are:
q6700 @ 2.66
3.3gb ddr2 800
hd 6850 1 gb.
60% of the time the frame rate is locked at 60 and dips to 55 but in busy scenes or even not busy scenes the frame rate dips and the game stutters. it doesnt make sense to me because i thought my ram would be my bottleneck not my cpu. does anyone know what could fix this without buying an entire new pc?
 

gomilly

Honorable
Oct 1, 2012
315
0
10,790
Looks like it is possibly my psu actually. When i run prime95 and kumbostor my gpu usage drops to 60-70% which it should not do because kumbostor is meant to push my card to 97-100% right?