Verdict: Zotac has applied a big overclock to an already fast GPU.
GeForce 8800 GTs only started rolling out of the Nvidia factory last month, but Zotac hasn't wasted any time in overclocking them. As we saw last month, a reference 512MB 8800 GT card is capable of outperforming a 640MB 8800 GTS, so overclocking isn't necessary to obtain decent performance from these new Nvidia cards. Extra speed, however, is never a bad thing.
Unlike the Asus EN8800GT we looked at last month, the Zotac 8800GT AMP! Edition doesn't include a bundled game. In fact, the only external feature that suggests this is a premium card is the presence of LEDs that make the fan of the standard single-slot Nvidia cooler glow orange. Underneath this fan is where matters become more interesting: Zotac has overclocked everything: the RAM, core GPU speed and stream processor frequency.
Arguably, the most important overclock is that of the stream processors. An 8800GT has 112 stream processors (16 more than an 8800GTS), which usually run at 1.5GHz. Zotac has added an extra 200MHz for a 1.7GHz overall speed.
The rest of the GPU has been clocked higher to match - a sensible move, as this means the hungry bank of stream processors will be fed more quickly with data, while any results from them will be output to your screen faster. The 8800 GT usually has a core speed of 600MHz, but Zotac has upped this to 700MHz. This may not sound much, but we could only raise the GPU on the Asus to 660MHz, and achieved a pleasing frame rate increase from this modest overclock.
The speed of the Zotac's RAM has also been upped from 900MHz (1.8GHz effective) to a hefty 1GHz (2GHz effective), increasing the memory bandwidth of the card from 57.6GB/sec to 64GB/sec. Increasing memory bandwidth allows a card to transfer more data from the on-board memory to the GPU and back, which helps when using high-detail textures, high resolutions or applying AA. Our test system drew 256W from the mains with the Zotac running flat out.
As you'd expect from a pre-overclocked card, the Zotac performed faster than a standard 8800 GT in every game we threw at it. All three standard test games were easily playable at 1,920 x 1,200 with high levels of AA and AF, which is impressive for a card costing less than £200. In the higher-resolution tests, the minimum frame rates with the Zotac were around 5fps better than those returned by the Asus at stock speeds, which is a decent if not spectacular boost.
Switching to Vista, and our DirectX 10 games, performance was altogether less impressive. The Zotac, like the rest of its 8800 brethren, couldn't handle Crysis with the settings ramped up. Setting the resolution to 1,680 x 1,050 with Very High detail settings resulted in a minimum frame rate of only 6fps and an average of 9fps. However, this score compares well with the performance of a standard £330 GeForce 8800 GTX, which scores a minimum of 8fps and average of 13fps in the same benchmark. Unreal Tournament 3, on the other hand, was a doddle for the Zotac, achieving a smooth minimum frame rate of 49fps at 1,680 x 1,050, only 3fps short of an 8800 GTX.
The clock speeds of the Zotac are already pretty high compared with basic 8800 GT cards and, when it came to overclocking, we immediately ran into problems. The core speed wouldn't budge an inch. The online benchmarkers are also stuck exactly at the 700MHz mark, so we suspect that there's some trickery going on in the BIOS of 8800 GT cards to prevent further overclocking - that, or Nvidia has already pushed the GPU as far as it will go. As overclocking the stream processors of a GeForce 8-series card is still a matter of using a graphics card BIOS editor, we were disinclined to attempt to overclock them. The card also started to return errors after negligible increases in memory speed. Clearly, Zotac has pushed this card to within an inch of its life.
Conclusion
As ATI is targetting a cheaper price point, the 8800 GT remains the best value high-performance card around. However, standard 8800 GTs can cost as little as £160 (such as the Zotac on www.play.com) and offer similar performance. A DIY overclock would further reduce the gap. As impressive as it is that Zotac released a heavily pre-overclocked card so quickly, £200 is steep.
