Page 13 - NVIDIA SLI & overclock performance charted
Skulltrail doin' SLI
What's interesting is that Skulltrail motherboard supports NVIDIA's SLI technology through the use of a couple of MCP chips, and the rich number of PCIe lanes allow for possible quad-SLI action. I smell some interesting GeForce 9800 GX2 reviews in the future :)
For those of you who don't know what SLI is allow me to explain it a bit; we take verbs like Crossfire & SLI for granted these days. Just like AMD's Crossfire NVIDIA's SLI is a situation where you add a second similar generation graphics card to the one you already have in your PC and effectively try to double or even quadruple your raw rendering / gaming performance.
The idea is not new at all though .. if you are familiar with the hardware developments over the past couple of years you'll remember that 3dfx had a very familiar concept with the Voodoo 2 graphics cards series. There are multiple ways to manage two cards rendering one frame, think of Supertiling, it's a popular form of rendering. Alternate frame Rendering, each card will render a frame (even/uneven) or Split Frame rendering, simply one GPU renders the upper or the lower part of the frame. So you see there are many methods where two or more GPUs can be utilized to bring you a gain in performance.
Now initially Guru3D tried to bring you guys a review based on CrossfireX, meaning two Radeon 3870 X2 cards combined (thus four GPUs active). Unfortunately the driver has not been finished; we had a chat with the ATI driver team last week and they can't get us even a beta to try out. Hopefully in march something more consistent will be released.
We therefore made the switch towards NVIDIA GeForce cards, two GeForce 8800 GTX 768MB graphics cards to be precise; which do not suck either. Once we add the second graphics card, we reinstall the NVIDIA ForceWare driver (we used 169.28 for the SLI test) and enable SLI in the NVIDIA control panel:
It's really fun to see an Intel based mainboard have SLI support all of the sudden. Anyway time for some results. We again measured Call of Duty 4 and did some testing with the very CPU dependant 3DMark06.
Now briefly I want to state that some websites will measure performance at 640x480 or whatever creepy resolutions just to show you the performance differential. I think that theory is utter BS; you do not spend so much dough on a system to check how fast the CPUs are at dwarf resolutions. We only settle for the real-word experience; whether you like such results or not is up to you.
Call of Duty 4
The reality is extremely harsh as yes, even in SLI we run into a graphics card bottleneck. You can notice that bottleneck at the flat-line in the charts. The first two results to the right are single card results, the first one the baseline performance from our main test-system. The second that same videocard yet on the Skulltrail system. Mind you that we do nearly double up performance with SLI enabled.
Then in the last three results to the right we scale CPU performance (with the SLI cards inserted) with steps of 400 MHz towards 4 GHz over the eight logical scores. It's pathetic ... the graphics cards seriously bottleneck the overall performance and therefore the results stay the same. This is the reality today in pretty much any game to date. You are either GPU limited and when you can use that CPU the game is usually programmed single-threaded.
Let's try 3DMark06 from who we know it loves multi-core CPU's and CPU scaling.
Again to the left the baseline test system (nForce 680i + 8800 GTX), then the GTX on the Skulltrail system (we immediately gain 1300 points).Then at the third result (middle) we add another VGA card and test in SLI, and go upwards to 16480 points instantly.
Now one step further to the right we overclock the system in steps of 400 MHz. The17924 Score is actually at 3.6 GHz; I did not label that correctly in the chart. Finally, to the right, we push the eight cores towards an astounding 4 GHz and then we end at 19155 points. Mind you that the two 8800 GTX graphics cards are running at default reference speeds here; these are not overclocked or tweaked at all.
I so wish that games would scale this well with faster CPUs and multiple logical CPU cores. Ah well, don't be afraid .. the future is near.