Nvidia 8800 Ultra doesn't like copulation

[Alpine]

SLI SLOdown


AS I WAS testing the un-announced Socket LGA775 CPU from Intel, on my reference Striker Extreme Nforce platform, I tried to put in a pair of GeForce 8800 Ultra reference design cards to check the performance numbers - one was a loaner from Nvidia.


No, The INQ is not on its love list, so no proper test kits there for us, the other came from Asus.

I equipped the system well: full custom air cooling for the heat pipes, Corsair Nautilus 500 high-power water cooler for the CPU, extra fans for the hidden pockets around the CPU socket, and Corsair Dominator DDR2-800 CL3 memory with its own triple-fan cooler. All this was fed by a high-grade CoolerMaster 850W power supply, with plenty of native 6-pin (but, interestingly, no 8-pin!) GPU power feeds.

The ForceWare was the newest one, too, version 158.22 for WinXP.
On its own, each card showed the expected performance, maxing out at around 645 MHz GPU / 1120x2 MHz memory speeds. By itself, that's quite good, but proper water cooling blocks like those from Thermaltake or Aquacomputer would surely bring this north of 700 MHz GPU / 1150x2 memory, as some of our fellow reviewers proved recently. 3DMark was completed, I got around 12,890 3DMark06 at UXGA 1600x1200 resolution with either card.

Interestingly, the "Optimal GPU speed" utility in Ntune application, found ~670 MHz GPU and 1260x2 MHz memory to be the choice, yet neither card could even start the first 3DMark test with it. So much for the Ntune, it's still better to do this stuff manually.
Anyway, I was itching with expectation, to see if I could come close to 20,000 3DMark06 UXGA.

But, what a disappointment - when I put both cards together and set them into the SLI mode, ensuring of course that all the power feeds are in place and connections are right, 3DMark crashed in the middle of the first test bench even at the default card speed of 612 MHz GPU / 1080x2 MHz memory! A repeat showed the same result.

Then I again ran that "optimistic" optimal GPU speed tool in Ntune. This time, it recommended 581 MHz GPU / 1080x2 memory, a setting barely better than the original 8800GTX! This is strange, two identical 8800 Ultra cards, both working fine on their own at overclocked 645 / 1120 speed, can't get together even at the default setting. Again, the drivers were the newest, the platform one of the best boards around, and no penny pinching on any of the components - what do you think is wrong here?

The INQuirer