Extreme overclocking

Posted at: Tuesday 28th February 2006 by Ben Hardwidge

They destroy expensive components for fun, they dabble with liquid nitrogen and they even mod beer coolers into PC cooling systems. Ben Hardwidge speaks to the extreme overclockers

Meanwhile, Barry can't wait to try using liquid nitrogen at his forthcoming event, and he isn't fazed by the safety issues either. 'The safety issues are mostly common sense,' he says. 'You have to use gloves and eye protection, and that's about it.' He then explains how it works, explaining that 'the liquid nitrogen comes in a 25-litre flask, and you pour it into a copper tube with a heatsink at the bottom that attaches to the CPU. You get ridiculous temperatures from it, such as -196˚C'.

Back on earth

You don't have to set up a lab like that of Dr Frankenstein to compete with the big guys in benchmarks though. Take Andrew's comparatively modest system, for example, which uses readily available parts. The CPU is cooled by a Prometeia Mach II at -55˚C, while the rest of the system is cooled by an Exos 2 water-cooling rig with an AQZ050 pump. So how has he managed to build such a fast system with these parts?

Andrew explains, 'I had the Mach II re-gassed with r507, which helps to keep the CPU temperature cool, even when the system is fully overclocked. Also, the CPU mount has been sanded down to help improve contact with the CPU.' The system is also packed with fans, and the end result is an Athlon 64 X2 4800+ with each core running at 3.168GHz with a voltage of 1.68V.

Volt-modding

Applying a higher voltage to a CPU will often enable you to get a higher overclock if your cooling setup is up to the job, but extreme overclockers will also do the same to their graphics cards. In fact, it's even seen as an essential mod by these guys.

'You have to volt-mod the RAM and the core on the 7800 GTXs, and change the BIOS,' explains Barry. 'The GTXs are massively underclocked. My cards had a core clock of 430MHz, but I'm now running them at 675MHz and you can only overclock them that far by increasing the voltage. The core runs at 1.3V as standard, and I increased it to 1.7V, while the RAM has been overvolted from 1.9V to 2.4V.'

The way that you volt-mod a component varies between different models, but it's rarely an easy job. In fact, when it came to volt-modding his pair of 7800 GTXs, Andrew admits, 'I paid someone else I knew to do the mod and had the graphics cards volt-modded to supply an adjustable amount of volts to the core and the memory.' Interestingly, Andrew also said that 'BIOS flashing the graphics cards was key to overcoming an in-built cold issue with the 7800GTX 512MB, as the cards have problems running below 35˚C.

You can also make your CPU voltage more stable by modding your motherboard too. Andrew explains, 'I had an ASUS P4C800-E once, which was a great overclockers' board, but it had a problem holding a stable CPU voltage when it was overclocked to the max. I got around this by adding a resistor to the board, which made it stable.'

Tips and tricks

Before I say goodbye, I ask Andrew and Barry if they have any tips and tricks for new overclockers. Andrew's first tip is 'a quick fix to improve GPU bandwidth, which is to increase the PCI-E bus from 100MHz to 110MHz when you're using 7800 GTX cards. I benchmarked my system at 120MHz, but I wouldn't recommend doing that. RivaTuner (www.guru3d.com) has loads of features that help squeeze out a few more hundred 3D marks as well. I love tweaking the RAM too, as it can get you loads of extra performance'.