With version 10.0 of Microsoft's DirectX programming interface arriving early next year, we can't expect graphics card manufacturers to make radical revisions just now. It's unsurprising, therefore, that ATI's Radeon X1950 XTX chip has a large number of similarities to its predecessor, the X1900 XTX. However, ATI has also found room for a few novel features and specifications you won't have seen before - and we reckon these make it the best-value true high-performance card on the market.

Arguably the most notable of these is the presence of GDDR4 (graphics double data rate, fourth generation) RAM. ATI was instrumental in bringing GDDR3 to the market, and it's played a similar role here.

The new GDDR4 RAM combines a lower voltage requirement with a fixed burst length that's twice as high as that of GDDR3. In essence, this means the memory needs much less power to run at the same clock speed, and can therefore be run faster.

Whereas the Radeon X1900 XTX had a memory core speed of 775MHz (1.55GHz with DDR RAM), the X1950 XTX can run its memory at a massive 1GHz (2GHz with DDR RAM). As a consequence, the memory bandwidth jumps from 49.6GBps (gigabytes per second) to 64GBps. Not only is this a huge step forward from the older Radeon X1900 XTX, but it's also significantly ahead of the 51.2GBps of nVidia's GeForce 7900 GTX, giving the Radeon X1950 a clear advantage over its main competitors.

In other respects, though, the X1950 XTX differs very little from the X1900 XTX. Generally this is no bad thing, because that card's 48 pixel-shader processors already significantly outnumbered those in the nVidia cards. Should games programmers ever start to write their code to take full advantage of pixel shader processors, the X1950 XTX will find itself in the driving seat.

The core clock speed is identical to the X1900 XTX, and both cards are built using the same manufacturing process. The cooling solution has been revamped from previous ATI designs, however, and the X1950 XTX is incredibly quiet considering its astonishing power, at least by enthusiast gamer's standards.

In terms of performance, the X1950 XTX falls behind the GeForce 7950 GX2. However, that card has two graphics chips rather than one, and costs almost half as much again as the X1950 XTX. The XTX should come in at a similar price to the GeForce 7900 GTX, which is bad news for the nVidia chip, since the Radeon proved to be faster - particularly at higher resolutions (1600x1200) and with full detail bolted on.

At 1280x1024, the cards are fairly similar. Even so, given the potential of the pixel shaders, we'd say the X1950 XTX was the better deal overall.