PCIe 1 - 60 fps; PCIe 2 - 25 fps

[rainman]

So, I was trying to see how another card would fit in my system and I came across an interesting find.

If I run my 8800GTX in PCIe 1, I get about 60 fps out of Real-Time HDR IBL. In PCIe 2, I get about 25 fps. Both slots are PCIe 2.0 x16. I wonder if there's some small architecture difference between slot 1 and 2. I shall have to go look.

The card also runs 15 C hotter in the #2 slot, just because the case limits the airflow into the fan on the HR-03. But that is to be expected.

 

[ring.of.steel]

The only thing i can think of is that the other slot is running at some kind of 8x or 4x mode for some unknown reason...

 

[bbf]

What OS are you running?

With my P35 Mobo with PCIe 1.0 x16 and x4 slots and ATI HD3870's.
In Windows XP 32bit the 3dmark06 values are about 10% less in the secondary slot
However in Windows Vista x64, 3dmark06 values are about 33% less in the secondary slot.

 

[ring.of.steel]

Hmm there seems to be somthing strange about that...

 

[Matrices]

I believe the documentation for the 650i SLI advises owners use slot 1 first and not slot 2. So at least in that chipset the manufacturers are aware of a performance difference.