Manufacturer:Sapphire UK Price (as reviewed): £900+ (inc. VAT) MSRP US Price (as reviewed): $1099 (exc.Tax) MSRP
Pre-overclocked graphics cards have been around for years and, while not for everyone, can offer that extra sliver of performance if you’re willing to foot the bill. What we regularly ask though is why manufacturers hold back so much? If our own experiences, many graphics cards yield decent amounts of overclocking headroom, yet pre-overclocked cards often settle for tiny overclocks of 3-5 per cent. Even watercooled pre-overclocked cards rarely stray beyond overclocks of 15 per cent.
Part of the reason is the availability and quality of individual GPUs and their ability to handle higher clock speeds, but Sapphire has taken note, and decided to really push the boat out with its new Radeon HD 5970 Toxic. Not only do both GPUs ship with a massive 24 per cent overclock, but the card comes fitted with twice the GDDR5 memory of the stock model, and a massively upgraded cooler too. Make no mistake, this is a pre-overclocked partner card done to the limits of what’s possible, to the point that the production run will be extremely limited; Sapphire tell us that less than one thousand units will be produced.
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Underneath the pomp, ceremony and huge cooler (more on that in a bit) though, this is still a Radeon HD 5970 card, already the most powerful graphics card on the planet even before Sapphire started tinkering. The Toxic is still 31cm (12.2in) long and is still built around two full-fat Cypress GPUs (codenamed Hemlock XT).
After Sapphire’s tweaking and the addition of the massive cooler, these GPUs run at 900MHz, up from the 725MHz of a stock-speed HD 5970. This theoretically makes the Toxic comfortably faster than two HD 5870s (which share the same GPU and are clocked at 850MHz) in CrossFire. To achieve these clock speeds, Sapphire has had to increase the GPU’s voltage, and this has necessitated the two 8-pin PCI-E power connectors used to fuel this beast. Sapphire recommends an 850W PSU for any PC that includes the Toxic.
The doubling of memory from 2GB on the stock HD 5970 to 4GB also requires extra power. This is doubly true, as Sapphire has chosen to use twice the number of DRAM chips, rather than use higher density 256MB modules, with 16 chips on either side of the PCB. This has required a slight PCB reshuffle, as well as extra power phases compared to the typical HD 5970, but the stock HD 5970’s PCB is roomy enough to allow for the extra memory without issue. The memory has also been overclocked, from 1GHz (4GHz effective) to HD 5870 speeds of 1.2GHz (4.8GHz effective).
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With the extra power coursing through its circuitry, not to mention the noise that a stock HD 5970 makes under load, replacing ATI’s stock cooler was a mandatory requirement for the Toxic – this is a likely reason why we’ve not seen many attempts at a pre-overclocked HD 5970 yet. Sapphire’s cooler is a monster fit for this purpose though; it’s a modified Arctic Cooling Accelero Xtreme H5970 triple-slot construction of heatpipes, aluminium fins and three slim-line 92mm cooling fans. We’d recommend leaving another slots-worth of space beyond this to allow the fans to work efficiently.
Each GPU is fitted with a copper contact plate through which run four nickel-plated copper heatpipes. These two sets of bi-directional heatpipes dump their heat into the cooling fins of the cooler, with the cooling fans blowing directly down through the fins and onto the PCB. The card also uses a backplate to cool the 2GB of GDDR5 memory mounted there. Due to the upped power demands of the card, there’s also a separate VRM heatsink that sits above the card’s power delivery circuitry, and which is secured by both thermally conductive tape, and screw-through bolts.
At the rear of the card are the usual pair of DVI ports and the mini-DisplayPort output, and the card supports three-screen Eyefinity. The Toxic is certainly a very impressive card on paper – superior to two HD 5870, with the advantage of having the two GPUs closer and fed by a PCI-E bridge chip, plus the significantly upgraded cooling. We were understandably eager to see how this monster of a graphics card performed.
Graphics processor 2 x ATI Radeon HD 5970, 900MHz
Pipeline 2 x 1,600 stream processors (900MHz), 2 x 32 ROPs
Memory 2 x 2GB GDDR5, 4.8GHz effective
Bandwidth 2 x 153.6GB/sec, 256-bit interface
Compatibility DirectX 11, OpenGL 3.1
Outputs/Inputs 2 x DVI, 1 x mini-DisplayPort, 1 x CrossFire