Overclocking

As the Asus HD 5870 ships set to the card's standard clock speeds, performance out of the box is identical to that of any other HD 5870 1GB currently on the market. The big difference then is how much of a difference the voltage tweak software can have when overclocking - we've previously pushed a stock HD 5870 to 925MHz on the core and 1,300MHz (5,200MHz effective) on the memory, improvements of nine per cent and eight per cent respectively.

While the voltage tweak software isn't the most intuitive application to overclock with, it certainly did the business when it came to overclocking the card's core and with a bump of 0.1v from 1.15v to 1.25v the card happily clocked up to 980MHz core! We weren't done yet though as with a further increase in the Vcore up to 1.3v we were finally able to crack the famed 1GHz core clock, settling on 1,005MHz - an eighteen per cent improvement of 155MHz over the card's stock speed. Memory overclocking was unaffected by the increase in Vcore of course, so our previous best stable setting of 1,300MHz (5,200MHz effective) still stands.

Thermal Performance

Putting realistic, repeatable load on a GPU to get a decent idea of its real world thermal output has long been something we've experimented here at bit-tech. We've found that Synthetic benchmarks such as FurMark thrash the GPU constantly, which simply isn't reflective of how GPU will be used when gaming. It's such a hardcore test that any GPU under test is almost guaranteed to hit its thermal limit, the mark at which the card's firmware will kick in, speeding up the fan to keep the GPU within safe temperature limits.

Conversely, simply leaving a game like Crysis running at a certain point also isn't reflective of real world use. There's no guarantee that the GPU is being pushed as hard as other titles might do, and the load will vary from play through to play through.

Eventually then, we've decided to use 3DMark06's Canyon Flight test as a real world representative, repeatable graphics test. It's a ferociously demanding test, pushing graphics cards to their limit, but also containing peaks and troughs in performance that match real world game play.

As the test is so demanding and GPU limited, we've set 3DMark to run the test at 1,280 x 1,024 with 0xAA and 16xAF (enabled in the driver), constantly looping the test for thirty minutes and recording the maximum GPU Delta T (the difference between the temperature of the GPU and the ambient temperature in our labs).



For analysis of these and all other results, please read the Results Analysis page.