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Review: NVIDIA GeForce 7800 GS AGP shootout

by James Smith on 26 July 2006, 08:21


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GeForce 7800 GS AGP

NVIDIA G70 GPU Properties for 7800 GS AGP
Process and Fabricator 110nm @ TSMC
Die Size 18.65mm x 17.9mm (334mm²)
Transistor Count 302 million
DirectX Shader Model Shader Model 3.0
Basic Configuration (VP/FP/ROP) 8/24/16
Set Configuration (VP/FP/ROP) 6/16/8
Vertex Shader Info VS3.0
5D FP32, co-issue MADD, branch, tex
Fragment Processor Info PS3.0
4D FP32, dual and co-issue MADD/MADD, branch, tex
ROP Info 4x FX8/FX16 MSAA (2 subsamples/cycle)
2x Z-only rate, 2x colour-only rate
FP/FX blender (inc. FP16)
Texture processing 24 FP32 address units, 24 samplers
Bi/Tri/Aniso (128-tap), FP16 filtering
Memory Interface 256-bit, 4 memory channels
GPU Interface PCI Express 16X
Display output 2x dual-link DVI TMDS transmitters, NVIDIA PureVidio

The G70 is paired with their BR02 PEG-to-AGP IC at clocks of 375/600, giving the following theoretical rates versus GeForce 6800 Ultra.

Theoretical Rates

Theoretical Rates for GeForce 7800 GS AGP and GeForce 6800 Ultra AGP
NVIDIA GeForce 7800 GS NVIDIA GeForce 6800 Ultra
Core Clock 375MHz 400MHz
Memory Clock 600MHz 550MHz
Pixel fillrate 3.00G pixels/sec 6.40G pixels/sec
Texture sampling rate 12.0G samples/sec 12.8G samples/sec
Z-only fillrate 6.00G samples/sec 12.8G samples/sec
Vertex transform rate 0.56G tris/sec 0.60G tris/sec
VP MADD issue rate 2.25G instr/sec 2.40G instr/sec
FP MADD issue rate 12.0G instr/sec 6.40G instr/sec
Memory bandwidth 38.40 GB/sec 35.20 GB/sec

You can see that 7800 GS bests 6800 Ultra in one crucial area, due to using G70 rather than NV40. While it's deficient elsewhere, the double MADD issue per-cycle per-unit in G70's fragment shader core helps 7800 GS to a pixel shading advantage over the still-impressive GeForce 6800 Ultra.

On top of that GeForce 7800 GS AGP gets G70's better texture filtering performance and better AA image quality (gamma corrected, transparency), compared to what's available on GeForce 6-series hardware. Being AGP there's no support for SLI, that technology requiring the user to make the leap to PCI Express for their graphics bus.

So it's a new SKU designed to motor through the latest shader-heavy games titles faster than the previous generation of high-end NVIDIA graphics products on AGP, whilst looking better to boot. Let's look at the retail examples we had for testing.