You might not think that many crimes have been committed in the name of progress - if it was a question on 'Family Fortunes', progress as an answer would probably earn you the 'uh-er' sound - but there's one devious act that comes to mind: the assassination of AGP.
It wasn't until we reviewed the ASRock 939Dual-SATA2 - the first motherboard with AGP 8x and 16x PCI-E slots - that we realised something we'd long suspected: the replacement of AGP in the name of progress wasn't quite the act of benevolence that the IT industry presented it as. PCI-E was progress in that it offered new features such as SLI, but speed-wise, it wasn't essential.
The Athlon 64's ascendancy meant that Nvidia and ATi's chipset business thrived, so the two companies have a vested interest in supporting their new chipsets with the latest and greatest GPUs. Unfortunately, this left the significant number of gamers who own AGP-based motherboards with no real upgrade options. Nvidia, however, has finally succumbed to popular demand, and announced a new 7-series GeForce GPU for AGP: the GeForce 7800 GS.
Initially, the 7800 GS appears to have the same trimmings as those of the PCI-E GeForce 7-series GPUs, such as full Shader Model 3 support and 256MB of top-end GDDR3 memory. Our 'Extreme Edition' XFX review model is even pre-overclocked, with the GPU running at 440MHz, up from the Nvidia reference speed of 375MHz, and the memory running at 650MHz (1.3GHz effective), rather than 600MHz (1.2GHz effective).
It looks as though Nvidia is welcoming back AGP with open arms, but don't crack open the champagne just yet, because there are a few snags. Firstly, that XFX trim; we first saw the holographic HSF on a GeForce 7800 GT, but, according to numerous readers, it was very difficult to get hold of, and was soon swapped for something a bit duller. It's back and it still looks good, but we'd advise you to check before placing your order to make sure you get the exact model shown in our pictures. Secondly, pieces of the XFX logo on the metal side panel of our review sample came off very easily. Upgrading yourself with pieces of a razor-sharp metal 'X' isn't a fun experience.
There's also the fact that the 7800 GS GPU isn't a straightforward AGP port of the PCI-E 7800 GT. Like the GT, the GS has a decoupled pixel pipeline design, with a different number of shader processors to ROPs. This approach is generally employed in the name of efficiency. However, while the 7800 GT has 20 pixel processors and 16 ROPs, the GS has 16 pixel processors and just 8 ROPs, which will limit its performance at higher resolutions, despite the relatively high clock speed. That said, it still has 16 texture processors, which means that it shouldn't suffer unduly in games that rely more heavily on texturing than shading. One area in which the 7800 GS improves on the 7800 GT is the HSF design, which is surprisingly quiet, though not silent.
PERFORMANCE
The last time we tested an AGP graphics card was in the June 2005 issue, almost a year ago. Rather than dig out the old AGP test PC, we decided to make use of the excellent ASRock 939Dual-SATA2 motherboard and create a new test PC capable of running both PCI-E and AGP graphics cards. However, we kept the overclocked 2.8GHz Athlon 64 FX-55 CPU, 74GB Raptor and 2GB of Corsair RAM from the old rig, so the benchmark scores that you see in this review are comparable with all the PCI-E graphics card reviews from the last few issues.
What's immediately apparent is that the GeForce 7800 GS's performance is disappointing. This is a 7-series card, but it can't even handle Battlefield 2, the least demanding of our benchmarks, at 1,600 x 1,200 with 4x AA and high AF. Its average of 36fps, with a minimum of 21fps, is well short of what's necessary for a smooth experience. XFX's own overclocked GeForce 7800 GT is roughly 33 per cent quicker, with an average of 54fps at the same settings.
To prove how undernourished certain parts of the 7800 GS's pipeline are, if you drop the AA at 1,600 x 1,200, its frame rates perk up. At 1,600 x 1,200 with no AA and high AF, the 7800 GS averaged 54fps, with a minimum of 31fps.
XFX's GeForce 7800 GT can't handle F.E.A.R. at 1,600 x 1,200 with 4x AA and 8x AF, but it can provide a great experience at 1,280 x 960 with 2x AA and 2x AF, where it averages 53fps. The 7800 GS averages 39fps at this setting, which is more than 25 per cent slower than its PCI-E relative. The story is the same in Quake 4, with the 7800 GS's frame rates tailing off the moment you apply more than 2x AA.
Its name might be similar to that of the GeForce 7800 GT, but the 7800 GS's performance is far closer to that of the GeForce 6800 GT - a card that's not only more than two years old, but also a card that was originally available in AGP. I dug out our old AGP GeForce 6800 GT and put it through its paces - you can see the results in the graphs on the opposite page. Despite being older, less technically advanced and less flashy, the 6800 GT doesn't do the 7800 GS any favours. At low resolutions, in both Battlefield 2 and F.E.A.R., the higher clock speed of the 7800 GS enables it to put some real distance between itself and the 6800 GT. However, upping the resolution and the AA settings brings down the 7800 GS. In Battlefield 2, at 1,280 x 1,024 with 2x AA, its average is 14fps higher, but increase the AA to 4x, and that margin falls to 9fps. At 1,280 x 960 with 4x AA in F.E.A.R., the margin is practically invisible.
The GeForce 6800 GT has been replaced by the lower-cost GeForce 6800 GS. We've only reviewed PCI-E versions of this card, but as we've yet to see a performance difference between cards using the PCI-E and AGP interfaces, we can meaningfully compare the AGP 7800 GS with the PCI-E 6800 GS. The 6800 GS has 12 pixel processors, four less than the 7800 GS, but 12 ROPs, four more than the 7800 GS. The XFX 6800 GS averaged 51fps in Battlefield 2 at 1,280 x 1,024 with 4x AA - exactly the same as the 7800 GS. The 6800 GS and 7800 GS's scores were also all but indistinguishable in F.E.A.R. at 1,280 x 960 with 2x AA and in Quake 4 at 1,280 x 1,024 with 2x AA.
Overclocking doesn't help to improve the 7800 GS's standing either. We pushed the core to 480MHz and the RAM to 700MHz (1.4GHz effective), but the benefit in terms of extra frames per second was minimal.
CONCLUSION
Testing the GeForce 7800 GS was a strange and stressful experience, partly because bits of it integrated with my hand, but mainly because the GeForce 7800 GS offered surprisingly little in the way of straight-line speed. It was like climbing into a Porsche, pressing the accelerator and rolling slowly forward instead of tearing away. The GeForce 7800 GS just isn't as quick as it should be.
At the resolution and quality settings that a £235 graphics card should be able to handle, it's barely any quicker than the GeForce 6800 GT or 6800 GS. Judging the card purely on its performance results, it looks as though Nvidia is out to exploit the GeForce 7800 brand.
If you own an AGP motherboard, and already have a high-end GeForce 6-series card then you should avoid the 7800 GS. Even if you have an older graphics card, such as a GeForce FX-series model or Radeon 9800, you should still avoid this product. Because the 7800 GS performs poorly at high resolutions, you can simply save £60 and instead buy a GeForce 6800 GS, which offers virtually identical performance at medium resolutions.
Author: Alex Watson
XFX GeForce 7800 GS Extreme Edition