Sapphire Radeon HD6990 4GB reviewed -

Here's a question for you. What's huge, blisteringly fast, very loud, needs its own power station and is not made by Nvidia? The answer is AMD's latest incarnation of the Northern Island range of GPUs, the Antilles, or to give it its marketing name, the Radeon HD6990. Oh, and incidentally, it's currently the fastest single card on the planet.

When the HD6*** series was launched, AMD caught everyone on the hop by tinkering about with the product numbering system so that the two original launch cards the HD6870 and HD6850 weren't direct replacements for the HD5870 and HD5850 - but because of the changes in the core architecture it allowed AMD to have cards with the same level of performance but at a much better price point.

Thankfully the HD6990 isn't about wishy washy stuff like trying to get the right amount of bang for your buck, especially when you see the price of the thing, no - this card is all about AMD trying to regain the king of the hill title for the fastest graphics card back from Nvidia, well, for a single card at least.

To get its frame crunching performance the HD6690 uses two, yes, two slightly down tuned high-end Cayman XT cores as found in the HD6790 cards. Both the core and memory clocks have been turned down in the HD6990, or at least out of the box as standard they have, but more on that later. The core and the 3072 stream processors fly along at 830MHz, down from 880MHz while the 4G of GDDR5 memory is clocked at 1,250MHz (5GHz effective) instead of the Cayman XT's normal 1,375MHz (5.5GHz effective).

The reason for its huge size - it measures a whopping 305mm (12in) in length, about the same as the previous generation's 5970 - is mainly down to trying to keep the two cores cool and for this it uses not one, but two Vapor Chamber heatsinks. One over each core separated by a very loud central fan.

To deliver power to the GPU and memory more effectively than its predecessor, the cores are moved further apart on the HD6990 than the HD5970 with the gap between them filled with power regulators and the PCI-E 2.0 bridging chip.

On top of the card there are two 8-pin PCI-E power connectors so you know that this baby consumes a fair amount of power. That's a bit of an understatement, as the HD6990 has been designed from the ground up to run at 450Watts. Out of the box it still needs 375Watts to get it going, the higher figure comes into play should you decide to ignore the warranty warning sticker.

What's this about a warranty warning sticker then? One of the features of the more recent Northern Island based cards is the fitting of a two way BIOS switch on the top of the PCB, which is handy if you like to tinker with the graphics card BIOS to make it run faster and muck things up badly, at least you have an option to get the card back to running normally.

With the HD6990 however, things are a bit different as the switch allows you to either run the card at the stock 830MHz of the HD6990 or at the normal speed of the Cayman XT core, that is to say 880MHz, which necessitates an increase in the voltage being fed to the chip.

So we have a factory fitted overclocking option, great, but hold on, what's this yellow warning sticker on the switch? It's a warning about voiding the warranty of the card by overclocking. It turns out we have a factory overclocked card that shouldn't be overclocked as chances are it will void the warranty – go figure.

As you might expect for one of the first cards to see the light of day, Sapphire's HD6990 is a reference design but with a new sticker on the cooler, but there has been some thought given about the cable bundle that comes with the card as it has an unusual arrangement of ports on the back panel.

There's single DVI and four mini-DisplayPorts, so Sapphire bundles in all you need to get going with a multi panel EyeFinity setup; a DVI to VGA adaptor, passive miniDP to DP, miniDP to SL-DVI and miniDP to HDMI dongles and an active DP to SL-DVI dongle. In Eyefinity mode, the HD6990 can currently support up to five screens, but when the DisplayPort 1.2 drivers eventually surface you will be able to daisy chain additional DisplayPort 1.2 monitors to each DP output.

To test, we're using an Intel Core i7 Extreme 965 3.2GHz processor and 6GB of Crucial PC3-10600 DDR3 which sits in an MSI X58 Pro motherboard, together with a Western Digital WD1500ADFD Raptor hard drive with Windows 7 Ultimate 64-bit installed and a Be Quiet 850 power supply.

To test the DirectX 11 capablilites of the card we used the DiRT2 game and Futuremark's latest 3DMark benchmark, 3DMark11, while the other two 3DMark Vantage and FarCry2 are DirectX10 only.

Benchmarks
3DMark Vantage

Far Cry 2

Far Cry 2 frames per second in Sapphire Radeon HD6990 4GB

3DMark 11

3DMark 11 overall score with the Sapphire Radeon HD6990 4GB

DiRT2

DiRT2 framerate tested with the Sapphire Radeon HD6990 4GB

Performance-wise the HD6990 is a monster, it kicks sand in every other single card's face and makes a decent fist of moving into dual card territory even at the default clock settings out of the box.

Building two of these beasties into a Crossfire set-up should lead to some awe-inspiring frame rates, that is if you've got over a grand to spend, have a huge full tower case and have a local power station to plug into.