Nvidia GeForce 7800 GTX

Far Cry is tested in three settings groups, across a set of standard resolutions. The first settings group has no IQ enhancements applied.

With no IQ enhancements applied, there's no benefit to running the 7800 GTX either on its own against a single 6800 Ultra, or as a pair against SLI 6800 Ultras. You need to make the cards work harder to see any gains with G70.

SLi beats a single board, obviously, but otherwise there's no advantage to using the 7800 GTX. Far Cry has a HDR rendering mode tailored to NV40 and G70, though.

The r_HDRrendering rendering variable is set to 7 for this test. Where 6800 Ultra shows no gains with SLI, a single 7800 GTX is not only faster than 6800 Ultra SLI, but SLI then shows large gains to be had with HDR rendering enabled. On average, SLI 7800 GTX is 30 per cent faster than a single board and it's the first time that Far Cry's HDR rendering has been accelerated to any kind of degree by either a single board or two in SLI.

Other settings for r_HDRrendering show even larger gains. G70's ROP hardware is responsible for the OpenEXR FP buffer compositing that Far Cry uses to apply HDR lighting to a frame. Combined with the new texture filtering performance for FP textures and you can see where G70 is getting its gains

Verdict

Nvidia's focus on fragment ALU improvements, from allowing sub-unit one to do a vec4 MADD in a single cycle and from increasing the number of full fragment ALUs from 16 to 24, are where the vast majority of the speed improvements in G70, compared to NV40, are to be found. Tweaks to the fragment rasteriser, the ROP hardware and the addition of two more vertex units are where you'll find the rest. It's a modest improvement which TSMC's 110nm process afforded Nvidia without too much work, the company looking like it's saving large-scale feature and performance enhancements for a product to come in nine months to a one year's time.

The improvements in performance where FP filtering and blending were concerned (see the last few shader tests in ShaderMark 2.1, along with the HDR tests in Far Cry) are impressive. Nvidia's changes in the texture filter hardware and ROPs combine to explain the new found FP performance, making the G70 attractive if that's the kind of rendering you're looking forward to in upcoming games. If only the hardware could multi-sample float buffers for new speed and image quality.

It's also nice to see an improvement to anti-aliasing quality with G70. Alpha-to-mask AA, for multi or supersampling alpha textures that are used to paint pixels, gives a boost in image quality that's been missing for some years, and gamma correct AA, where the final colour of the pixel is modulated to match your monitor's usual gamma, is welcomed on consumer Nvidia hardware. That the performance hit is acceptable is the icing on that cake.

SLi performance seems to be higher at first glance, although another article is likely needed to investigate further. Finally, the question of CPU limitation rears its head yet again. With hardware so powerful, you waste it to some degree without a CPU and memory subsystem to keep it fed. Finding cash for an FX-57-alike isn't easy. In that respect, it's nice to see this generation of new 3D hardware releases slow down somewhat. ATI is still a little while away from releasing R520 and Nvidia hasn't rolled out the 7-series range-topper yet.

Only lacklustre video support (especially with my recent acquisition of a Sony PSP and a big desire to playback MPEG-4 AVC video on my PC) spoils it for me somewhat. Single-slot cooling and dual-link DVI support (even from just one of the outputs) makes me a happy hardware reviewer.

All-in, a solid improvement to an excellent architecture. Nvidia balances ALU increases with ROP considerations to create a formidable pixel pusher that currently has no equal. 7800 GTX boards can be bought from today for a UK retail price of £369. That's only some £70 more than a 6800 Ultra - ie. spend 15 per cent moe for a 40 per cent increase in performance.

Nvidia remains in the Shader Model 3.0 driving seat with an all-powerful new chip that looks forward to WGF 1.0, 90nm and even better pixel output silicon. The fastest graphics card money can buy, unsurprisingly. And I would be even less surprised if the entire initial UK allocation of boards is sold by the end of the day, such is its power and ability.

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