One feature of the GeForce 6800 Ultra catches the eye immediately: there are two power connectors. We saw something like that in the Volari Duo V8 Ultra and had expected to see that here: 220 million transistors and memory working at 1100MHz call for an appropriate power supply. It is another fact that really left us flabbergasted – NVIDIA recommends that you use a 480W and higher Power Supply Unit (PSU) to ensure stable work of the new GeForces! You don’t often find such a PSU even in hardcore overclockers’ systems; they don’t definitely come in mainstream system cases. Thus, the potential owner of a GeForce 6800 Ultra has to shell out about $100-150 for a proper PSU like those from Thermaltake – I don’t think this will add popularity to the new GPUs. Fortunately, our testbed had a 550W PSU inside so we had no power-related problems running our tests.
Quiet Cooler for a Powerful Card
The card itself looks less imposing than its predecessors (GeForce FX 5950 Ultra and GeForce FX 5900 Ultra). The major reason for that is NVIDIA’s decision to use a smaller more compact single-slot cooling system on heat pipes. To be precise, the system occupies one slot and a half rather than two slots, but anyway takes less space than previous cooling systems from NVIDIA. In any case, the PCI slot located right next to the AGP will be occupied with the cooling systems.
A centrifugal blower is still used for creating the air circulation. Considering the number of transistors (220 million) and the frequencies (starting at 400MHz), we have little hope for a noiseless cooling, notwithstanding the heat pipes. The fan still can’t automatically adjust its rotation speed. It is connected to the PCB with two wires, which signifies the absence of a tachometer.
The cooler design deserves a separate mention in our review, since it is pretty outstanding I should say. The heat is taken off the die via a thin-rib aluminum heatsink stuck to the chip with a thin layer of high-quality thermal paste. In our case the heatsink is a monolith one, i.e. the ribs and the footing are a solid piece of metal, which ensures higher heat dissipation efficiency. The fan hidden inside a plastic housing blows the air through this heatsink and then through the memory cooling system, which is also designed in a very interesting way. The memory chips are covered with an aluminum plate of an unusual shape, which dissipates the heat. However, since the chips located at the upper edge of the PCB do not get cooled by the air stream generated by the fan, their heat is moved along a flat heat pipe within reach of the air flow. The heat pipe there is equipped with an additional thin-rib heatsink section, which serves to dissipate the heat generated by GDDR3 chips. The thermal interface between the memory chips and the heatsink is the same as in case of GeForce FX 5950 Ultra: special fibrous pads sodden with white thermal paste. They appeared to be very efficient.
The GDDR3 memory chips are made by Samsung and work at the nominal 600MHz (1200MHz DDR) with the 1.6ns access time. However, in case of our GeForce 6800 Ultra sample they worked at a slightly lower frequency of 550MHz (1100MHz DDR). Despite much higher working frequencies, Gddr3 memory generates considerably less heat than GDDR2: the memory heatsink of our GeForce 6800 Ultra was just a little bit warm at work, just like the reverse side of the PCB opposite these chips. Finally the high-end graphics adapters got rid of this eternal GDDR2 spell: tremendous heat generation. Since GDDR3 is a much more convenient memory type than GDDR2, its share in contemporary graphics accelerators will only grow.
I was surprised to find out that the new cooling system is rather quiet. To be more exact, it generates quite a bit of noise when you start your computer and reboot it. In a little while the fan rotation speed management system calms down, as the temperature remains low enough and reduces the fan rotation speed, which makes the level of generated noise much lower, though you can still hear this fan. When you start 3D applications the fan doesn’t speed up to the utmost of its power like we saw with GeForce FX 5950 Ultra, so playing games with the new GeForce 6800 Ultra promises to be quite a pleasant occupation. I assume the fan speeds up only if the core temperature grows up to a certain threshold.