HIS ATi Radeon X1900 XTX

It's barely three months since ATi launched its new range of X1000 graphics cards, but there's already a new addition at the top of the range. What's more, the X1900 is based on an entirely new piece of silicon, codenamed R580. The X1900 XTX has no fewer than 48 pixel pipelines, up from the 16 of the X1800. The core clock is running at 650MHz, 25MHz more than the X1800 XT's clock of 625MHz. The X1900 XT runs at 625MHz, with its RAM also running 50MHz slower.

While the frequency difference may seem small, ATi claims the X1900 does so much work per clock that actual performance drops significantly with clock speed. It's also worth remembering that the CrossFire Edition master card is an XT and so will throttle an XTX back to its speeds when in CrossFire configuration. The XTX is for single-card systems only.

The huge increase in pixel shaders is a gamble for ATi. On the one hand, the increased transistor count leads to more chance of defects in any given chip and therefore potentially lower yields. On the other, the extra pixel pipelines provide more power for higher resolution gaming today and the ability to run the high-detail games of tomorrow. These games will include ever more pixel shader-intensive rendering techniques such as parallax occlusion mapping, which gives a better impression of rough, bumpy, non-flat surfaces than bump mapping can.

Predictably, the X1900 XTX raced savagely through tests. Half-Life 2 at our standard 1,280 x 1,024 with 4x AA and 8x AF ran at a stomach-turning 109fps, while Far Cry sped along at 63fps. Upping the resolution to 1,600 x 1,200 saw the same score in Far Cry (testament to the extra pixel rendering power) and an insignificant drop to 94fps in Half-Life 2.

Even Call of Duty 2, with all its settings turned to maximum, posed little problem for the X1900 XTX. At 1,280 x 1,024, we saw 47fps, and 38fps at 1,600 x 1,200. This is our toughest test, and the X1900 XTX outperforms the GeForce 7800 GTX 512 - nVidia's top-end hardware - by about 20 per cent at both resolutions: the Asus Extreme N7800GTX 512MB scored 39fps and 32fps at 1,280 x 1,024 and 1,600 x 1,200 respectively.

There's a high price to pay for this massive performance, though, and it's only worth it if you have a monitor capable of 1,600 x 1,200. For top performance at 1,280 x 1,024, try the £250 Sapphire X1800XT from www.micro direct.co.uk, which is still capable of around 60fps in most games at 1,280 x 1,024.

Also beware that nVidia will announce its new GPU in the next month or so. While we wouldn't normally recommend holding off for a few weeks - if so, when would you ever buy, after all - the lure of nVidia's next-generation silicon makes it worth waiting to see who will finish with the title of fastest card available.

Author: Clive Webster