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 6800 to 7800).
Aside from the improved manufacturing process which results
in a smaller core size, 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 Asus model is clocked at 520 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 (Asus clocks the memory at 1.44
GHz). 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 7900
series supports two Dual-link DVI connectors with a maximum resolution up to
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
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
|Number of Transistors
|Core Clocks (Vertex, Core in
|Memory Clock (MHz / data
|Vertex Shaders (#)
|Pixel Shaders (#)
|Frame Buffer Size
|Memory Bandwidth (GB/s)
|Texture Fill Rate (# Pixels
pipes x clk) in Billions/sec
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. Now, what's all this
about XHD Gaming?