Sapphire ATI Radeon HD 4850 TOXIC

Overclocking

Before we start talking about overclocking, it's worth mentioning the simply astonishing difference between the Sapphire HD 4850 TOXIC's and the stock HD 4850's cooling solutions. The stock HD 4850 idles at around 80-85°C (in an ambient room temperature of 23°C), although this is in part due to ATI forcing the cards fan to a low speed setting to avoid it becoming a hairdryer. In comparison, the Zalman VF900 cooled HD 4850 idles at a mere 45°C in the same ambient temperature, and at its stock speeds it never exceeded over 50°C!

This is even more impressive when you consider that at load the VF900 Zalman cooler is noticeably quieter than the stock ATI cooler, although at idle it is perhaps a little noisier than the lower RPM, but much, much hotter stock cooler, due to the VF900's fan not having a variable fan speed.

With the enormous extra cooling overhead of the Zalman VF900 we really hoped to push this card much further than its out of the box overclock, and certainly weren't disappointed. We started out using ATI's Overdrive facility in the Catalyst driver, and easily pushed the HD 4850 TOXIC to 700MHz core and 1,200MHz memory clocks - the absolute maximum offered by the software. This achieved a result of 28.25 FPS in Crysis running at 1680x1050, high detail, 0xAA, 0xAF.

As these were the highest settings possible while using AMD/ATI's driver we had to look elsewhere to further improve performance, finally finding a separate AMD GPU Clock tool which allowed us to manually set the clocks to whatever we liked, without running the risk of bricking the card with a BIOS flash to unlock extra headroom.


With this tool it was simple to further increase the core and memory clocks, although we soon encountered stability issues at speeds in excess of 700MHz on the core. The highest stable clock we were able to secure was 725MHz core and 1,200MHz (2,400MHz effective) on the memory, producing a result in the same Crysis test of 31.45 FPS, an astonishing eleven percent improvement in performance!

It's clear that the vastly improved cooling supplied by the VF900 unlocks a lot of performance potential from this card, and we're sure with enough tweaking it could be moved even closer to the HD 4870 in many benchmarks. We've heard it's quite possible to achieve stable core speeds nearing 800 MHz thanks to this cooler and a volt-mod. However fun this might be, you risk some serious damage going down this avenue.

Value and Final Thoughts

On the face of things the Sapphire Radeon HD 4850 TOXIC looks like a pretty poor choice for those looking to grab a budget graphics card. It finds itself in the no-man's land of being a good £30 more expensive than the cheapest HD 4850 cards on the market, and only £35 less than the cheapest HD 4870, which it trails by a good few FPS in most tests.

However, the cooling advantage brought by the Zalman VF900, which sells for £15 separately, (and that's before you void your warranty by fitting it), is certainly worth the price of admission, as are the performance improvements brought by Sapphire's decent pre-overclock, and the perfectly stable 700 MHz/1,200 MHz core and memory overclocks available in the ATI overdrive settings that are all made possible by the improved cooling setup. It's certainly been nice to be able to remove a Radeon HD 4850 from our test setup post-benchmark and not need oven gloves.

Overall, the Sapphire is a welcome addition to the ever growing field of Radeon HD 4850s and is certainly a reasonably attractive prospect priced as it is between the budget 4850s and 4870s. You might pay a premium in comparison to the entry level versions of the card, but in exchange you get a solid bundle, a fantastic third party cooling solution that knocks nearly 40°C off the core temps at load and a whole lot of overclocking headroom.

With performance that can almost rival that of a Radeon HD 4870 if you overclock it to its full potential, the Sapphire Radeon HD 4850 TOXIC is a great choice for those of us that are happy to tweak our hardware to maximise performance. However, if you're just looking to buy a card, and drop it into your system without overclocking it further, the price premium doesn't make as much sense, and a stock card for £30 less might be a better alternative.

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