Overclocking The EAH5870
For our next set of performance metrics, we spent some time overclocking the Asus EAH5870 using the Overdrive utility built into ATI's Catalyst drivers and using Asus' SmartDoctor utility, which gives users the ability to tweak not only clock speeds, but the GPU voltage as well.
Without any voltage modifications, we were able to overclock the Asus EAH5870 to a respectable and fully stable 900MHz / 1.29GHz. That was basically the upper limits of what Overdrive could do, before Asus sent over an update for the card's BIOS. With the card flashed to the shipping BIOS and using SmartDoctor to alter the GPU voltage, however, we were able to take the card much higher. With a bump in GPU voltage to 1.35v, we took the Asus EAH5870 all the way up to a 1GHz GPU clock with 1.3GHz memory.
While we had the card overclocked, we re-ran a couple of benchmarks and realized a marked improvement in performance. ET:QW showed the larger gain, but L4D was mostly CPU limited, hence the smaller increase in performance.