With the Sapphire ATI Radeon HD 4850 Toxic Edition, Sapphire delivers an enhanced ATI 4850 graphics card with a boosted clock speed and effective Zalman cooler.

We got a chance to ttest Sapphire's Radeon HD 4870 card a few weeks ago and we were pretty impressed. Both its performance and graphics quality levels were incredibly competitive for the price and the 4870 was a clear winner. Our admiration for ATI's latest graphics chipset has only grown since then as it leads the pricier nVidia GeForce GTX 260.

This month, we've turned our attention to the 4850 card – a still cheaper version of the ATI 4800 range. Indeed, Sapphire's HD 4850 is such good value it is able to squeeze itself into the £150-and-below graphics card chart.

Nor is this an ordinary rendition of the 4850 chip. Sapphire routinely offers special Toxic Editions of its best cards that ramp up the clock speeds or memory, or come with an enhanced cooling system. With the Sapphire ATI Radeon HD 4850 Toxic Edition, Sapphire delivers in two of those three areas.

The Sapphire ATI Radeon HD 4850 Toxic Edition's memory is a standard 512MB of GDDR3 - a major difference between the 4870 and the 4850 is that the latter comes without the 4870's GDDR5 RAM. However, the memory clock speed is ratcheted up from 993MHz (1,986MHz DDR effective) to 1.1GHz (2.2GHz DDR effective).

Similarly, there's a standard 256bit memory interface, but the Sapphire ATI Radeon HD 4850 Toxic Edition's basic memory bandwidth of 63.6GBps is raised to a more palatable 70.4GBps. The core clock speed has also been upped from 625MHz to 675MHz.

For many users, the most interesting aspect of the Sapphire ATI Radeon HD 4850 Toxic Edition will be the Zalman cooler. It's considerably more effective than those typically found on graphics cards and we found the Toxic extremely quiet and efficient.

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