Sapphire HD 4870 Toxic

Verdict: A vapour chamber cooler but the results are disappointing.

As is the case with most new GPUs, when the ATI Radeon HD 4870 first hit the shelves, no matter which manufacturer's name was on the packaging, the card, cooler and clock frequencies were all identical. Now manufacturers are producing variants on the reference design, with custom coolers and higher frequencies. The Sapphire HD 4870 Toxic is one such card, shipping with a factory overclock and using a vapour chamber cooling system to drastically lower the GPU temperature.

The innovative Vapor-X cooler is Sapphire's own design, and an update of the cooler used on the Sapphire Atomic HD 3870. The new design is a totally sealed unit that relies on the evaporation and condensation of water via a series of wicks. Water is held in a transportation wick on the hottest side of the vapour chamber, nearest the GPU. The heat causes the liquid to vaporise, and then rise through the vaporisation wick into the condensation wick. The liquid cools and condenses here, then soaks back into the transportation wick, ready for the cycle to be repeated. The air pressure in the chamber is lowered to reduce the boiling point of the liquid, increasing cooling efficiency.

The Vapor-X cooler makes a significant difference to the GPU temperature. The HD 4870 Toxic ran at 65?C when folding, a full 19?C less than the temperature produced when running the same work on an HD 4870 card overclocked to the same level as the Toxic and using the reference cooler.

The Toxic ships with slightly higher clock frequencies than those of a standard HD 4870. The GPU clock has increased from 750MHz to 780MHz, while the 512MB of GDDR5 memory runs at 1GHz (4GHz effective), rather than the 900MHz of a standard card. This means that while the standard HD 4870 has 115GB/sec of memory bandwidth, the HD 4870 Toxic has 128GB/sec.

With the Toxic running at its stock speed, we saw some performance improvement over a £170 standard HD 4870. At 1,920 x 1,200, the Toxic achieved an average frame rate of 82fps in Race Driver: GRID compared to the 78fps average of the reference HD 4870. The minimum frame rate was 68fps compared to 63fps on a stock card.

Call of Duty 4 at 1,920 x 1,200 ran similarly to GRID, with the Toxic averaging 64fps compared to 61fps with a stock HD 4870. The minimum frame rate was 39fps, compared to 37fps with a stock card.

However, considering that the Toxic costs around £210, its closest rival on price is a stock-speed 216-stream processor GeForce GTX 260 card, with Zotac's GeForce GTX 2602 costing £210.32 inc VAT from Novatech. This card is more than a match for the Toxic in Crysis, with a minimum of 24fps at 1,680 x 1,050 compared to the Zotac's 28fps minimum. The Toxic was faster in our other two test games, however, with a minimum of 39fps in CoD4 at 1,920 x 1,200 compared to the Zotac's 35fps, and a minimum of 68fps in GRID as opposed to 53fps.

With the Toxic running the Canyon Flight test of 3DMark06, our test system's power draw peaked at 361W. While running the Folding@home GPU client, it drew up to 267W, and produced 3,533ppd from project p4743 with little noise.

With the superior cooling of the Vapor-X technology, we were keen to see how far we could push the Toxic. To start with, we used the ATI AutoTune function in the Catalyst Control Center, which raised the GPU clock to 810MHz and a memory frequency to 1.16GHz (4.64GHz effective). Our standalone overclocking tools couldn't raise these frequencies any higher while retaining stability. A higher GPU core clock speed caused the system to lock up completely, while a higher memory frequency resulted in artefacts.

Crysis benefited a little from the extra speed: we saw an increase of 1fps in the minimum frame rate at both 1,280 x 1,024 and 1,680 x 1,050, from 28fps to 29fps, and 24fps to 25fps respectively.

Conclusion

If you run the Sapphire HD 4870 Toxic at its default speeds, it doesn't offer enough performance improvement to justify its considerable price hike over a standard Radeon HD 4870. You could buy a stock HD 4870 for £170 and overclock it yourself, although it won't have the excellent Vapor-X cooler, so it will run hotter and noisier than the Toxic. Only if you value cool-running components and low noise levels is the Toxic is worth considering.