Overclocking, Power, and HeatOverclocking
I was quite eager to push this particular card, and in a way it did impress. I did not achieve the 1 GHz overclock that I may have been hoping for, but I did see a nice jump from the standard 810 MHz. The board would run for a while at 940 MHz core, but would eventually freeze up. 930 MHz turned out to be quite stable. I was able to clock the memory to 1400 MHz without any real problem. GDDR-5 does have error correcting ability, so pushing memory speed too high will actually make it slower rather than exhibit rendering errors.
Voltage adjustments are not included with this particular card, and are certainly not available in the standard AMD Overdrive control panel. Afterburner does have a slider that controls voltage, but it is not enabled for this particular card. Perhaps another card in the near future? At 932 core and 1400 memory, the HD 6950 did surpass the GTX 480 in nearly every benchmark, and had an overall increase in performance around 8% to 10%, depending on the application.
Power and Heat
I do not have a reference HD 6950 for testing, but from all appearances it seems that the MSI Twin Frozr is about 6C cooler overall than the reference design. I also wanted to see how temperature compared across the board for these three cards.
The GTX 480 runs hot. You can really hear it too. The HD 6950 does very well, considering it is running nearly as fast as the HD 5870, and has a chip with a significantly higher transistor count. Even overclocked the MSI card does not get significantly hotter than at stock speeds. Now let us see how power works.
The AMD cards all clock down quite nicely at idle, and the GTX 480 is not all that far behind. Once any kind of strenuous rendering is enabled though, we see some real separation here. The GTX 480 is way higher when it comes to power draw, while the two AMD cards at stock clocks are right next to each other. Again, with being a much larger chip, the HD 6950 does very well in the power department. Once we overclock the card though, we see a nice little jump in power consumption.