Sapphire Radeon HD 6990 CrossFire Graphics Card Review
The Sapphire Radeon HD 6990
Sapphire package their 6990 in a box which looks similar to many of their other products, the two models on this packaging signifying the dual GPUs we assume. Inside the bundle can be split into two sections, the standard items which include an invitation to Sapphires excellent Select Club and a CrossFire bridge. The second batch of items are DisplayPort converters which we will look at later.
6990 / 5970
6990 / 580 / 5970 / 6950
Shown above is the Sapphire 6990 with its heatsink artwork which differs from the reference design however the rest of the card is identical. In the centre is a single red cooling fan and this is a 12" card with a black, metal backplate on the rear which lets us see the location of the two GPUs as well as the single CrossFire connector which will allow us to join two cards together.
In terms of comparison with the 5970, single GPU 6900 and GTX 580, the 6990 is comparable in length with the card it is replacing and 0.75-1.0" longer than the single GPU models.
One of the first things that AMD/Sapphire were keen to tell reviewers was that the 6990 is designed not to be taken apart. The reason for this is that AMD are using a new thermal material between the GPUs and the vapor chamber heatsinks which sit on top of each. When warmed for the first time this new thermal material changes phase and should the cooler be removed it will never perform at the same level, instead we would need to re-apply different paste.
Shown above is the card in various states of undress and from those images we can see that AMD use copper plates on the GPU blocks and thermal pads for the memory and AMD branded PCIe 2.0bridge. The memory used on the reference card is Hynix branded and it also features large slave VDDC regulators which are designed to increase efficiency and lower power circuitry temperatures as well as reducing draw.
By placing these regulators at the centre of the card and moving the GPUs further apart when compared to the 5970 AMD state that they can deliver power to each GPU and its memory more effectively.
Speaking of power, this is a card rated for 375w (37w idle) and to meet this specification AMD have again included PowerTune technology. AMD PowerTune is a feature which has its roots in the theory that games use less power than application such as Furmark which are designed to stress components in a way that doesn’t reflect real world use. Through analysing the power use of a product when gaming AMD can create a power profile, limit a card to a particular TDP and dynamically adjust clocks so that we always get maximum performance from the card when gaming but when less demanding sections occur the card tailors its power use accordingly. The end result is a product which is much more flexible in terms of clock speeds available but AMD also realise that end users like to have full control of their products and so they have included user options within OverDrive.
For outputs on this card we have a layout which has more in common with custom 5970 Eyefinity designs than any previous AMD reference models. We have a single DVI connector and beside this are four mini-DisplayPorts. This choice of outputs has two impacts, firstly it allows Sapphire to bundle various connectors for DVI, full size DisplayPort and HDMI. Then secondly the main result is a wide range of connectivity options for Eyefinity which include 5×1 portrait layout. For power inputs the Sapphire 6990 has two eight pin connectors and hidden away, next to the Crossfire connector, in a similar way to the 6950/6970 is a small BIOS switch.
On those older products this switch was intended for recovery of bad flashes by enthusiasts. On the 6990 AMD and Sapphire have expanded on this, knowing that the card would be used by high end users. With the switch in position 2 we have a card which uses a BIOS clocked at 830MHz core (1250MHz memory) with the GPU receiving 1.12v. On position 1 the card is clocked at 880MHz core with 1250MHz memory and the GPU gets a bump to 1.175v to enhance overclocking potential with AMD’s press slides stating 990MHz+ as achievable.
In terms of other specifications we have a card with 3072 stream processors, 192 texture units, 64 ROPS and each GPU has access to 2GB of memory (256-bit bus) for a total of 4GB. The card fully supports PCIe 2.1, DirectX 11 and DirectCompute along with acceleration of high definition content and AMD’s latest image quality optimisations such as morphological anti-aliasing which we saw on the 6950/70 previously. Finally, the 6990 can output 7.1 audio over HDMI including DTS Master Audio and Dolby TrueHD.