AMD Radeon HD 6990 4GB Review

Written by Harry Butler

March 8, 2011 | 07:57

Tags: #12in #6990 #directx-11 #dual-gpu #eyefinity #hd-6990 #overclocking #radeon-hd-6990

Companies: #amd #ati

Radeon HD 6990 4GB Specifications

With two full-fat Caymen XT GPUs, the total number of stream processors inside this 12in-long card is a staggering 3,072. However, these run at 830MHz rather than the 880MHz of a single-GPU HD 6970 2GB. This has resulted in a horrifically high maximum power draw for the card of 375W – you’ll need a hefty PSU to handle this power-hungry card and still be able to run the rest of your PC.

As the GPUs are just the same as the Caymen XT GPUs used in the HD 6970 2GB, each has a 256-bit memory interface and the same 32 ROPs, two tessellation units and two rasterisers. As the memory of the HD 6990 4GB runs slightly slower than that of the HD 6970 2GB, however, the memory bandwidth for each GPU is slightly less at 160GB/sec rather than 176GB/sec.

However, the HD 6990 4GB has a dastardly trick up its sleeve in the form of the Antilles Unlocking Switch, which overclocks each GPU by 50MHz and overvolts them to keep this stable. While this overclock is a standard feature of all HD 6990 4GB cards, it will void your warranty and also boost the power consumption of the card to an incredible 450W. As such, you should only use this switch if you have a high-wattage, high-quality PSU – the card alone will nom through 31.25A of current.

AMD Radeon HD 6990 4GB Review Radeon HD 6990 4GB Specifications
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Aside from its extreme power consumption and AMD's efforts to tame the heat - using a vapour chamber cooler for each GPU as well as some exotic TIM - the HD 6990 4GB also boasts a super-sized selection of connections. As well as solitary CrossFire connector enabling four-GPU CrossFire craziness, the card also offers a dual-link DVI port and four mini-DisplayPort 1.2 ports.

Worry not though, Eyefinity users, because AMD is shipping a passive connector to convert one mini-DP output into a single-link DVI connection, plus an active alternative and a passive mini-DP to HDMI convertor. That should ensure Eyefinity support for any screen setup. It’s certainly good to see that easy Eyefinity support is high on AMD’s priority list with this graphics card, as triple-screen gaming can be excellent.

 AMD Radeon HD 6990 4GBAMD Radeon HD 6970 2GBAMD Radeon HD 6950 2GBNvidia GeForce GTX 570 1.5GBNvidia GeForce GTX 570 1.3GB
CodenameAntillesCayman XTCayman ProGF110GF110
Stream Processors2 x 1,536 (830MHz)1,536 (880MHz)1,408 (800MHz)512 (1,544MHz)480 (1,464MHz)
Layout2 x 24 SIMD Engines24 SIMD Engines22 SIMD Engines16 SMs, 4 GPCs15 SMs, 4 GPCs
Rasterisers2 x 22244
Tesselation Units2 x 2221615
Texture Units2 x 9696886060
ROPs2 x 3232324840
Transistors2 x 2.6bn3.6bn2.6bn3bn3bn
Size2 x 389mm²389mm²389mm²520mm²520mm²
Frequency1.25GHz (5GHz effective)1.375GHz (5.5GHz effective)1.25GHz (5GHz effective)1.02GHz (4.08GHz effective)950MHz (3.8GHz effective)
Bandwidth2 x 160GB/sec176GB/sec160GB/sec192.4GB/sec152GB/sec
Card Specifications
Power Connectors2 x 8-pin PCI-E1 x 6-pin, 1 x 8-pin2 x 6-pin PCI-E1 x 6-pin, 1 x 8-pin PCI-E2 x 6-pin PCI-E
Maximum Power Draw375W250W225W244W219W
Idle Power Draw37WNot SpecifiedNot SpecifiedNot SpecifiedNot Specified
Recommended PSUNot SpecifiedNot SpecifiedNot Specified550W550W
Typical Street Price£530-£550£270£220£400£300

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