Dual 512MB cards for SLI
GeForce 7900 GT SLI
While rumors were rampant that the G71 GPU used in the GeForce 7900 GTX and 7900 GT would contain as many as 32 pixel pipelines, G71’s architecture is fundamentally very similar to G70. The following chart summarizes the key differences between the two GPUs:
|GeForce 7900 vs GeForce 7800 Specs|
|GeForce 7900 GTX||GeForce 7900 GT||GeForce 7800 GTX 512MB||GeForce 7800 GTX||GeForce 7800 GT||GeForce 7800 GS AGP|
|Core Clock Speed (Vertex, Core)||700/650||470/450||550/550||470/430||440/400||375/375|
|Memory Clock Speed||800||660||850||600||500||600|
|Number of Vertex Shaders||8||8||8||8||7||6|
|Memory Bandwidth (GB/sec)||51.2||42.2||54.4||38.4||32||38.4|
|Pixel Fill rate ||10400||7200||8800||6880||6400||3000|
|Texture Fill rate||15600||10800||13200||10320||8000||6000|
|Dual-link DVI?||Yes (2x)||Yes (2x)||Yes (1x)||Yes (1x)||Yes (1x)||No|
As you can see from looking over the above table, the GeForce 7900 GTX and 7900 GT shares the same basic architecture as the GeForce 7800’s that they replace. You’re still looking at a 24-pixel shader GPU with 8 vertex shaders and 16 ROPs, yet NVIDIA is adamant that G71 is more than just a die shrink of G70. NVIDIA wouldn’t get into specifics but they did mention that they’ve incorporated improvements into G71’s ROPs to make them more efficient at FP blending, while SuperAA performance has been improved. Finally, NVIDIA has also integrated two dual-link TMDS transmitters into the GPU, making it ready to drive two dual-link displays such as Dell’s new 30” LCD the 3007WFP at resolutions as high as 2560x1600 (the native res of the Dell panel).
It’s also important to note that NVIDIA manages to pull all this off with fewer transistors than those that were required for the GeForce 7800’s G70 GPU, 278 million transistors in G71 versus 302 million for G70. NVIDIA is also quick to point out G71’s diminutive (for a high-end GPU) die size of 196mm2. This compares favorably to R580, which boasts a die size nearly twice as large at 352 mm2 and G70 at 334 mm2. With a considerably smaller die, G71 should be even cheaper for NVIDIA to produce than G70, assuming equal yields.
NVIDIA’s PureVideo technology carries over unchanged from previous GeForce GPUs, with three separate video engines allowing 720p, 1080i, and 1080p high definition output and support for a wide range of DVD/video playback features as well as H.264 acceleration.
Like the original GeForce 7800 GTX 256MB, NVIDIA clocks the graphics core and vertex engine independently of each other on the GeForce 7900 GTX and 7900 GT, with the vertex engine running 50MHz faster than the graphics core on the 7900 GTX card, and 20MHz higher than the rest of the graphics core on the GeForce 7900 GT. These margins also remain the same when overclocking via Coolbits or RivaTuner.
In terms of pricing, based on our conversations with NVIDIA’s board partners, we expect prices on the GeForce 7900 GT to start at about $299, with 7900 GTX boards retailing for $499. XFX and EVGA gave us even more specifics:
|GeForce 7900 GTX Board Pricing|
|EVGA e-GeForce 7900GTX KO SUPERCLOCKED||$TBA|
|EVGA e-GeForce 7900GTX SUPERCLOCKED||$519.99|
|EVGA e-GeForce 7900GTX||$499.99|
|EVGA e-GeForce 7900GT CO SUPERCLOCKED||$339.99|
|EVGA e-GeForce 7900GT CO||$319.99|
|EVGA e-GeForce 7900GT||$299.99|
|XFX GeForce 7900 GTX XXX (700MHz) 512MB||$599.99 |
|XFX GeForce 7900 GTX EXTREME (690MHz) 512MB||$549.99 |
|XFX GeForce 7900 GTX EXTREME (675MHz) 512MB||$524.99 |
|XFX GeForce 7900 GTX (665MHz) 512MB||$509.99 |
|XFX GeForce 7900 GTX 512MB||$499.99 |
|XFX GeForce 7900 GT XXX (560MHz) 256MB||$349.99 |
|XFX GeForce 7900 GT EXTREME (550MHz) 256MB ||$329.99 |
|XFX GeForce 7900 GT EXTREME (520MHz) 256MB ||$309.99 |
|XFX GeForce 7900 GT (470MHz) 256MB ||$299.99|
As you can see, both EVGA and XFX have planned to produce “stock” 7900 GT and 7900 GTX boards that follow NVIDIA’s reference speeds to the letter, and a line of factory overclocked cards that sell for a slight premium. While we don’t have the final clocks for EVGA’s boards, we do know that XFX is shooting for very high clock speeds with their highest-end GeForce 7900 GTX board, the XFX GeForce 7900 GTX XXX Edition 512MB board, with a core clock speed of 700MHz while the memory runs at 900MHz. For $50 less you can get the XFX GeForce 7900 GTX EXTREME 512MB which runs at 690MHz core/875MHz memory and at $525 the XFX GeForce 7900 GTX EXTREME 512MB
runs at 675MHz core/850MHz memory.
Among the GeForce 7900 GT boards, XFX’s most ambitious card is the XFX GeForce 7900 GT XXX (560MHz) 256MB, this card ships with a 560MHz graphics core and 825MHz memory for $350. Two 7900 GT Extreme boards are planned, one running at 550MHz core/815MHz memory, and a second SKU with a 520MHz core and 750MHz memory.