Hard on the heels of its super-fast, 1GHz cored Atomic Edition version of the ATI HD4890 comes Sapphire's HD4890 Toxic, again overclocked from the factory, this time with the core running at 960MHz.

Why produce two overclocked cards with the same GPU? You may well ask. The answer is that finding cores that ran stably at 1GHz was a time-consuming task and it turns out that not many were capable of running at such a high speed, so yields were low. Many more were found to be capable of running at slightly lower clock speeds than 1GHz, hence the HD4890 Toxic Edition.

The reference HD4890 core (or RV790 if you prefer) is built on a 55mn process and manages to cram 956M transistors onto a 282mm² die and as standard is clocked at 850MHz, backed by 1GB of GDDR5 memory running through a 256-bit bus at 975MHz. This, because of the way GDDR5 memory works, adds up to an effective memory speed of 3.6GHz and a huge bandwidth of 124.8GB/s.

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For the Toxic HD4890, Sapphire has tweaked the core to run at 960MHz: not as spectacular as the 1GHz Atomic, perhaps, but still a hefty 110MHz over the standard speed. As with its faster sibling, the memory speed has been increased by a mere 8 percent to get a clock speed of 1,050MHz (4.2GHz effective) which should help keep frame rates up when playing memory-hungry games at high resolutions.

To help keep the overclocked core and memory running stably, Sapphire has replaced one of the two 6-pin PCI-E power connectors on the card with an 8-pin power connector, but if your power supply doesn't have one of these 8-pin connectors, fear not; Sapphire bundles one 8-pin-to-Molex connector with the card, along with a 6-pin one.

Not only has Sapphire overclocked everything, it has also pulled off the neat trick of making it quieter than the standard card at the same time, thanks to the fitting of a Vapor-X cooler. The Vapor-X was first seen on Sapphire's special 1GB and 2GB versions of the HD4870, although the one used on this card is a variant of the one that Sapphire used on its HD4870 1GB Toxic.

The cooler uses a large aluminium base plate that covers not only the GPU but also the Qimonda IDGV1G-05A1F1C-40X memory modules. The copper GPU contact plate has three copper heatpipes (nickel plated) which run through the cooling fin stack, at the centre of which is 90mm fan keeping everything cool. It is a neat, compact and above all quiet cooling solution. To keep the power components cool there is a separate aluminium heatsink covering the PWR chips.

So what's the performance like? In a word, stunning, especially when you consider its price point. When benchmarked with Futuremark's latest 3DMark Vantage test using the High test (1,680 x 1,050 pixels) the Toxic eclipsed the standard version, scoring 7,725 as opposed to the standard card's 6,931.

In real world gaming it's a similar picture. When tested with Far Cry 2 at a 1,680 by 1,050-pixel resolution and with 2x Anti Aliasing switched on, the standard card gives a score of 61fps while the Toxic gives 66fps; and drops just 2fps when the resolution is increased to 1,920 by 1,200 pixels. Even with Crysis Warhead it produces playable frame rates at the same 1,680 by 1,050 resolution, scoring 38fps compared to the standard version's 31fps.

Bundled in the box is everything you need to get the Toxic set up. Besides the previously mentioned power adaptors you get a CrossFire bridge, TV out cable and adaptor, DVI to VGA and DVI to HDMI adaptors. On the software side there is CyberLink's PowerDVD and DVD Suite and a benchmarking disc. Sapphire backs the card with a two-year warranty.

Sapphire is well known for producing special cards and the Toxic version of the HD4890 is another to add to that list. Stunning performance for the price, with the neat trick of not only being much faster than the standard card, but also much quieter thanks to that Vapor-X cooler.