Overclocking the two cards setup in SLI
Overclocking the two cards setup in SLI
As most of you know, with most videocards you can apply a simple series of tricks to boost the overall performance a little. You can do this at two levels, namely tweaking by enabling registry or BIOS hacks, or very simply tamper with Image Quality. And then there is overclocking, which will give you the best possible results by far.
What do we need?One of the best tool for overclocking NVIDIA and ATI videocards is our own Rivatuner that you can download here. If you own an ATI or NVIDIA graphics card then the manufacturer actually has very nice built in options for you that can be found in the display driver properties. Based on Rivatuner you can alternatively use MSI AfterBurner which will work with 90% of the graphics cards out there. We can recommend it very much, download here.
Where should we go?
Overclocking: By increasing the frequency of the videocard's memory and GPU, we can make the videocard increase its calculation clock cycles per second. It sounds hard, but it really can be done in less than a few minutes. I always tend to recommend to novice users and beginners, not to increase the frequency any higher than 5% on the core and memory clock. Example: If your card runs at 600 MHz (which is pretty common these days) then I suggest that you don't increase the frequency any higher than 30 to 50 MHz.
More advanced users push the frequency often way higher. Usually when your 3D graphics start to show artifacts such as white dots ("snow"), you should back down 10-15 MHz and leave it at that. Usually when you are overclocking too hard, it'll start to show artifacts, empty polygons or it will even freeze. Carefully find that limit and then back down at least 20 MHz from the moment you notice an artifact. Look carefully and observe well. I really wouldn't know why you need to overclock today's tested card anyway, but we'll still show it.
All in all... do it at your own risk.
Now this was not really surprising, but as you can see, the card can overclock much MUCH higher and that has a very positive effect on overall performance. At default you'll easily lift the card over 800 MHz on the core.
Since we feel that 800 MHz and the memory at 4000 MHz (effective) is something anyone can and probably will achieve we'll take that as an example for this overclock session.
| Original | This sample | Overclocked |
| Core Clock: 675MHz | Core Clock: 675MHz | Core Clock: 800MHz |
| Shader Clock: 1350Hz | Shader Clock:1350Hz | Shader Clock: 1600MHz |
| Memory Clock: 3600MHz | Memory Clock: 3600MHz | Memory Clock: 4000MHz |
Now we left fan RPM control at default in all circumstances. And even with two cards in SLI, the system remains under 40 DBa, perfectly silent. Temps did go up to 75 Degrees C on the GPU though, but that is still perfectly fine. So let's have a look at some examples while overclcoked.
COD: Modern Warfare 2, maxed out quality settings as before with 4xAA 16xAF
All the way down a single GTX 460 768MB, then two setup in SLI mode, and the red bar is the SLI setup overclocked on both GPUs to 800 MHz core 4000 (effective datarate) memory.
Anno 1404, maxed out quality settings, same as before with 4xAA 16xAF
If you look at 1280x1024 you'll notice that the SLI results and overclocked results are the same .. that's the CPU being bottlenecked and thus it can not feed the two processors enough data fast enough. After that resolution the GPU overclock starts to show again.
And yes 3DMark Vantage benefits as well. We reach a 24k GPU score and the same for the overall P score, quite nice.
