The GeForce 7900GT name should indicate to users that the difference between it and the preceding GeForce 7800GT/GTX is minimal (unlike the jump from GeForce 6800 to GeForce 7800).

Aside from the improved manufacturing process which results in a smaller core size, and lower cost, there are really no architectural differences between the 'G70' and 'G71' GPUs.

If you recall, nVIDIA chose to stick with 0.11 micron manufacturing process for the 'G70' and instead experimented with newer manufacturing techniques on its lower end products. Now that TSMC has the 0.09 micron manufacturing process down pat, nVIDIA has given its 'G70' core a refresh and so the 'G71' is born.

The new nVIDIA GeForce 7900GT core contains a hefty 278 million transistors (which take up an area of 196 square millimeters vs. 352 square millimeters for the ATi X1900 core), which is less than the 7800GTX's 302 million. The 7900GT GPU is normally clocked at 450 MHz but the MSI NX7900GT-VT2D256E-HD GPU is clocked at 500 MHz. Its pixel pipeline has remained the same at 24, and the vertex pipeline at 8.

The GeForce 7900GT core continues on with Intellisample 4.0 technology, CineFX 4.0 engine and supports DirectX 9.0C and OpenGL 2.0.

The memory controller remains at 256-bits, and the GDDR3 memory has a default clock speed of 1.3 GHz. Once again the MSI NX7900GT-VT2D256E-HD has its memory clocked higer, up 210MHz to 1530 MHz. The dual 400 MHz RAMDACs will support dual monitors with a maximum resolution of 2048x1536 at a staggering 85 Hz. Anyone with a large 16:9 widescreen LCD will like the fact that GeForce 7900GT series supports two Dual-link DVI connectors with a maximum resolution up to 2560x1600.

Dual-Link DVI doubles the power of transmissions and provides an increase in speed and signal quality. This is necessary for extremely high resolutions as single-link DVI connectors do not support enough bandwidth. For instance, a single-link DVI at 60 Hz can only display a resolution of 1920x1080, while a DVI dual-link display can go as high as 2560x1600.

Two new GPUs in the Geforce 7900 Series

Here is a break down of the two new GPUs introduced by nVIDIA as compared to the current Geforce 7800s. You can see there are a few minor changes between the classes, but essentially the features are the same.

GeForce 7900GT/GTX VS 7800GTX Specifications 7900GTX 7900GT 7800GTX-512 7800GTX Manufacturing Process 90nm 90nm 110nm 110nm Number of Transistors 278M 278M 302M 302M Core Clocks (Vertex, Core in MHz) 700/650 470/450 550/550 470/430 Memory Clock (MHz / data rate) 800/1600 660/1320 850/1700 600/1200 Vertex Shaders (#) 8 8 8 8 Pixel Shaders (#) 24 24 24 24 Memory Interface 256-bit 256-bit 256-bit 256-bit Frame Buffer Size 512MB 256MB 512MB 256MB Memory Bandwidth (GB/s) 51.2 42.2 54.4 38.4 Verticies/Seconds (million) 1400 940 1100 940 Texture Fill Rate (# Pixels pipes x clk) in Billions/sec 15.6 10.8 13.2 10.32 Bus Technology PCI Express PCI Express PCI Express PCI Express

Despite the die shrink, the power requirements for the GeForce 7900GT have increased from what the Geforce 7800GT consumes. In a single 7900GT videocard situation, nVIDIA recommends at least a 400W power supply with 22 Amps on the 12V rail. Two GeForce 7900GT videocards running in SLI will obviously draw more power, and for this nVIDIA recommends power supplies in the range of 500-600W with 30 Amps on the 12V rail.

In any case, users contemplating a spiffy new GeForce 7900GT videocard should check out nVIDIA's list of approved power supplies first.