View Single Post
Old 07-17-08, 07:43 PM   #33
Neospy
Registered User
 
Join Date: Apr 2006
Posts: 7
Default Re: SLI issues/concerns and stuttering (GTX 200, 8, and 9 Series)

Quote:
Originally Posted by grimreefer View Post
all these unanswered questions!
I'll try to answer...
Quote:
Originally Posted by grimreefer View Post
im fascinated by this stuttering thing.
could it be caused by lack of bandwith on the pci express slots on the cheaper mobo's and would overclocking the pci express clock lessen it?
No
Quote:
Originally Posted by grimreefer View Post
does it happen on both vista 64 and vista 32,
Yes
Quote:
Originally Posted by grimreefer View Post
and is it lessened by having 4 gigs of ram or more on a 64 bit os?
No

The stuttering is caused by non-uniform frame times. Example:
1. GPU1 gets available.
2. The game prepares frame for GPU1.
3. it takes 5ms for CPU to prepare a frame
4. GPU2 gets available.
5. The game thinks it takes (5ms) to render a frame, it updates the scene for 5ms interval.
6. The game prepares frame for GPU2.
7. it takes 50ms to render frame on GPU1.
8. GPU1 gets available.
9. The game thinks it takes (50ms) to render a frame, it updates the scene for 50ms interval.
....
As a result, you will get 2 almost identical images with little delay between them, then long delay, then another 2 almost identical images and so on.

The slower your CPU, the longer it takes to prepare a frame -> less stuttering.

So, there are 3 options to reduce stuttering:
1. Buy very very slow CPU
2. Disable AA, AF, shadows etc to make the game CPU limited
3. Enable Vsync (which doesnt work well in SLI because of lack of Triple Buffering, performance is about the same as with single card+TB)
Neospy is offline   Reply With Quote