Overclocking tests
OverclockingThe usual disclaimer first. Samples' overclocks aren't necessarily indicative of retail models. Overclocking was conducted on each card by raising the core 10MHz at a time until instability set in. The same procedure was used for memory overclocking. A single 120mm fan was aimed directly at the cards when raising speeds and fan speed, if adjustable, was raised to maximum. The XFX GeForce 7800 GT was successfuly overclocked from its default (although overclocked when compared to standard 'GTs) 450/1050MHz speeds to 502MHz core and 1160MHz RAM. That represents a core overclock of around 11% and a memory headroom of around 10%.
The SAPPHIRE RADEON X1800 XL frequencies were adjusted using ATI's in-built Overdrive utility; no third-party tweakers worked correctly. From the default 500/990MHz we were able to raise speeds to 574MHz core (the maximum permitted by the application) and, somewhat surprisingly, only 1060MHz RAM before corruption set in. DOOM 3 and Far Cry were re-run with the overclocked settings on both cards.
A case of each benchmark suited either card. What's interesting is how the XFX GeForce 7800 GT, once overclocked, beats out a GeForce 7800 GTX in both tests. Food for thought.
