I am the owner of an ASUS G73J notebook equipped with a Mobility Radeon HD5870. I was very excited about the fact that the notebook has dedicated fan and cooling system for both the CPU and the GPU.
Since I never heard the GPU fans increase to a higher speed, I thought there must be some tuning potential inside the laptop, and as a first try I'd try to play around with OC. I had to find out that OC is on tilt by the VGA BIOS. I found a relatively easy way to update the VGA BIOS with a version that keeps all funcionality, but allows OC. (A modification of an official BIOS by a fan)
The results are great, it was posted on several places that reference 700/1000MHz (shader/memory) clocks can be OCed to a stable pair of 800/1100. (I tried to play around a little longer, but couldn't find other stable clock pairs) I ran some applications and heavy load games and my suspicion was true, there is room for great tuning potential. This 10-15% increase in clocks raised LuxMark score under Win 7 64-bit from 1550 to 2050. The machine is very stable and temperatures remain 'low'. Fans turn up at 76C and can push it down to 75C, no matter the load (FurMark). Unfortunately the fans slow down and it bounces between 75-76, which is more annoying than staying at high fan speed steadily.
I know that ASUS warranty most likely will not apply anymore to the VGA, still I found this to be good experience which might be of use elsewhere also. Anyhow, let me ask the expert overclockers: since this is a Juniper based product and the desktop variant (HD5770) has stable clocks of 850/1250, is there a chance that might work? I do not want to cranck up the clocks too high and fry the card. The fact that high fan speeds can turn heating around sometimes back to 74C might let me conclude that stable high fan speed could allow stable temperatures of 76-78 roughly.
What is your opinion?
Most important question however. I realized that OpenCL performance is a lot better under linux (and I develop there more often), but the same clocks resulted in the utterly quick and dreadful death of XServer. Why is that the same clocks cause to crash the driver under linux?
PS: BTW this is why I am very much surprised by MSI, who has an awesome housing for both GX680 and GX780 (just recently), and both housings have double air outlets, but one is kept closed and only one fan is inserted. The fact of having dedicated fans for CPU and GPU could allow for manufacturer OC, and this 15% increase in shader clocks resulted in 25% performance increase. That is HUGE! I don't know why they don't use their housings properly...