Radeon HD 6850 & 6870 review

Overclocking the R6870

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 to 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 tools for overclocking NVIDIA and ATI videocards is our own Rivatuner. If you own an ATI or NVIDIA graphics card then the manufacturer actually has some 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 really recommend it, 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, to not 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 we left the fan RPM control at default in all circumstances. We reached a very decent overclock guaranteeing better results. Voltage tweaking is not yet an option. With AfterBurner (download here) our stable end result was roughly 950 MHz on the core and 4344 MHz on the memory.

Here we have the card with  Call of Duty: Modern Warfare 2, maxed out image quality settings as before with 4xAA 16xAF, keep in mind that the light orange line represent baseline 6870 performance and the dark red one the overclocked performance. It's another 10% perf totally for free.

As you can see the increased clock did not offer that much extra performance, we see this quite a bit with high-end ATI products.