Specifications
| Mars/2DI/4GD3 | GeForce GTX 295 | GeForce GTX 285 | GeForce GTX 275 |
Chip | 2 x G200 | G200 | G200 | G200 |
Process | 55 nm | 55 nm | 55 nm | 55 nm |
Transistors | ca. 2.8 Mrd | 2 x 1.4 Mrd. | ca.1.4 Mrd. | ca.1.4 Mrd. |
GPU clock | 648 MHz | 576 MHz | 648 MHz | 633 MHz |
Shader (MADD) | 2 x 240 unified | 2 x 240 unified | 240 unified | 240 unified |
Shader clock | 1476 MHz | 1242 MHz | 1476 MHz | 1404 MHz |
Memory | 2 x 2 GByte GDDR3 | 2 x 896 MB | 1024 MB GDDR3 | 896 MB GDDR3 |
Memory clock | 1200 MHz | 999 MHz | 1142 MHz | 1134 MHz |
Memory interface | 2 x 512 Bit | 2 x 448 Bit | 512 Bit | 448 Bit |
Memory bandwidth | 2 x 158'976 MB/s | 223'800 MB/s | 158'976 MB/s | 127'008 MB/s |
ROPs | 2 x 32 | 2 x 32 | 32 | 28 |
TMUs | 2 x 80 | 2 x 80 | 80 | 80 |
TAUs | 2 x 80 | 2 x 80 | 80 | 80 |
Shader model | SM4 | SM4 | SM 4 | SM 4 |
Max TDP | > 250 Watt | 289 Watt | 183 Watt | 219 Watt |
Cooling
Designing a card which is based on two GTX 285 GPUs, but only comes with one cooling block, one of the biggest problems you'll end up with, is an adequate cooling solution. Compared to the GTX 295 ASUS overworked the GTX 295 cooler completely. Now you get eight heatpipes. Two copper base plates transport the dissipation power directly to the heatpipes from where it goes to the numerous fins. Paired up with a powerful radial fan ASUS obviously seems to be able to cope with the immense TDP of those two GTX 285 GPUs.
Dissipation power
If we look at the dissipation power these times we can only speculate. If ASUS really put two GTX 285 GPUs into one PCI-E slot their cooler has to be able to transport more than 350 Watts of heat to the environment. Probably ASUS also found different ways to reduce the TDP (Thermal Dissipation Power) of the whole card. What would have been relatively easy is reducing the shader clock. Therefore you would have gotten two adavantages: the card is more generous with temperatures and the dissipation power can be reduced. But ASUS really set the target to put two fully fledged GTX 285 GPUs into one PCI-E slot.
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