Noise, overclocking

Let’s see what the noise level is like by using a sonometer placed 5 cm from the fans of each card.

For once, logic prevails and the ranking stays the same as that of the power consumption at peak! If the HD 3870 X2 manages to be silent in idle (inaudible once in the casing), its fan accelerates very quickly (usually when the game’s menu appears). Fortunately, we are far from the level reached by the same fan on the HD 2900 XT and the noise is decreasing despite almost unchanged power consumption. On the other hand, contrary to what the sonometer seems to indicate, the difference with the discrete GeForce 8800 Ultra remains pronounced.

Overclocking

As for the HD 2900 XT, the HD 3870 X2 drivers’ Overdrive section is only available if a PCI Express 8 pin connector is plugged. It’s also the only way to overclock the card today, all the other software failing to be up to date in the mean time.

The reference card given by AMD hasn’t been able to gain a single megahertz GPU wise, but the memory has managed to reach the maximum allowed by the drivers, meaning 955 MHz. The Powercolor card (based on the standard design) managed to push the GPU to reach 855 MHz and 955 MHz for the GDDR3 chips. Our Italian and German teams were able to push the GPU up to 878 MHz and also get 955 MHz for the memory.

The margin is quite narrow when it comes to computational throughput, with a 4 to 6% gain. Memorywise, it’s impossible to tell as we’re obviously limited by the drivers and the majority of HD 3870 X2s seem to be able to go beyond 955 MHz (but how far beyond?). This isn’t surprising however given the presence of chips certified to work at 1 GHz.