A fan is fastened above the heatsinks – a thin aluminum plate directs the air stream along their ribs:

Again, the card is based on the NVIDIA GeForce 6800 GT graphics processor (NV40 core) that is normally clocked at 350MHz:

Like the GeForce 6800 Ultra, the GT model has 256MB of GDDR3 memory, but its frequency is reduced to 1000MHz. The reference card uses 2ns GDDR3 chips from Samsung:

The card did well at overclocking: the maximum stable frequencies were 420MHz GPU and 1150MHz memory. That’s really a nice performance bonus – the card exceeded the clock rates of the GeForce 6800 Ultra!

I reached those clock rates using the standard cooling system and without any other tricks. Let’s now check the card with a water-cooling system by installing the Aquarius II from Thermaltake:

The stable frequencies are 450/1150MHz now.

The GPU frequency only grew up by 30MHz: this 420-450MHz range may be the overclockability peak for this particular sample of the NV40 without voltage adjustments or extreme cooling solutions. Anyway, those 450 megahertz – 28.5% above the nominal frequency – are good by themselves.

The maximum frequency of the graphics memory didn’t change with the installation of the water-cooling system on the GPU – that’s natural. 1150MHz is not too much for graphics memory chips that are normally clocked at 1000MHz. However, we deal with GDDR3 here, and this memory remains a kind of stranger – we haven’t yet explored its potential fully. Maybe those 1150MHz (or 15% above the nominal frequency) are a good result after all.

So, the frequencies of the GeForce 6800 GT easily exceeded the regular clock rates of the GeForce 6800 Ultra at overclocking.