HIS Radeon HD 6990 Crossfire review

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The Specifications


The Specifications

So then, it is based on two Cayman GPUs, now we can describe the product very easily. Take a Radeon 6970 and multiply everything by two. And that is roughly the R6990 in a nutshell, features and specification wise, yet now it's one card.

Now before I show you the final specifications of the Radeon HD 6990, you need to understand that the card has two modes, normal and unlocked.

The AMD Radeon HD 6990 graphics card features dual-BIOS capabilities. This feature is controlled by an Unlocking Switch sitting closely next to the CrossFireX connector on your board. The switch toggles between the factory-supported Performance BIOS of 375W TDP (BIOS1), and a more extreme Performance BIOS (BIOS2) that unlocks higher clock speeds and up to 450W TDP of performance.

For end users to enable this higher performance BIOS, they will have to remove a label covering the dual BIOS switch and set the BIOS switch to the desired position outlined below:

  • Position 1 Extreme Performance BIOS (BIOS2).
  • Position 2 (default shipping position) factory-supported Performance BIOS (BIOS1).

Let's place that in a table:

  Radeon HD 6950 Radeon 6970 Radeon 6990 Radeon 6990 Unlocked
Fab Process 40nm 40nm 40nm 40nm
Die Size 389 mm2 389 mm2 389 mm2 x2 389 mm2 x2
Transistors 2.64 Billion 2.64 Billion 5.28 Billion 5.28 Billion
Core Clock / MHz 800 880 830 880
Memory Clock / MHz 5000 5500 5000 5000
Memory Bandwith 160 GBps 176 GBPs 320 GB/s 320 GB/s
Memory type GDDR5 GDDR5 GDDR5 GDDR5
Shader processors 1408 1536 3072 3072
Compute performance 2.25 TFLOPS 2.7 TFLOPS 5.10 TFLOPS 5.40 TFLOPS
Color ROPs 32 32 64 64
z/Stencil ROPs 128 128 256 256
TDP Gaming 140 W 190 W 350 W 415 W
Idle power 20 W 20 W 37 W 37 W

The Radeon HD 6990 comes armed with an astonishing 3072 shader processors, thus 48 SIMD based shader clusters, split up in a twofold engine per GPU. The domain and shader clock is locked in at 830 or 880 MHz. The card comes paired with 4 GB of memory clocked at (effective) 5000 MHz (2GB per GPU). The TDP of this product is 350W in default mode, and in unlocked mode the card can consume 415W with a hefty game. There's room left for overclocking in the unlocked design though, you may take the card up-to roughly 450W.

Now, since we have all this knowledge let's just compare this product with some others. Let's have a quick comparative overview of some of the specifications representing a certain scope of other performance parts, you'll notice that the differences are just HUGE, I've inserted the "default" performance mode in there, not the unlocked one:

Specifications Radeon HD 5770 Radeon HD 5850 Radeon HD 6850 Radeon HD 6870 Radeon HD 6950 Radeon HD 6970 Radeon HD 6990
GPU Juniper XT Cypress Pro Barts Pro Barts XT Cayman Pro Cayman XT Cayman XT
Manufact. tech. 40nm 40 nm 40nm 40nm 40nm 40nm 40nm
GPU frequency 850 MHz 725 MHz 775 MHz 900 MHz 800 MHz 880 MHz 830 MHz
Stream processors 800 1440 960 1120 1408 1536 3072
Memory Datarate 4800 MHz 4000 MHz 4000 MHz 4200 MHz 5000 MHz 5500 MHz 5000 MHz
Memory bus  128-bit 256-bit 256-bit 256-bit 256-bit 256-bit 256-bit x2
Memory buffer
Power consumption
108W 151W 127W  150W 150W 190W 350W
Idle Power
- - 19W 19W 20W 20W 37W

Impressive stuff... huh? The card of course is an up-to-date DX11 class product with a couple of new features. Features wise, the graphics cards will be very similar to the last generation products and is merely an advanced, updated model. However some features like one DVI and four DisplayPort 1.2 monitor connectors are present for a full Eyefinity experience up-to five cards with just one R6990.

Now before you get concerned about the four DP connectors, the card will ship with 3 adapters to enable Eyefinity gaming out of the box for all users. The product will ship with:

  • 1x mini DisplayPort to passive single-link DVI adapter
  • 1x mini DisplayPort to active single-link DVI adapter
  • 1x mini DisplayPort to passive HDMI adapter

The adapter configuration will enable 3x1 gaming out of the box with DVI panels but with additional display adapters or Display Port displays you will be able to drive up to 5 displays in portrait Eyefinity (5x1 Portrait mode) for the rather grand gaming experience.

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