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Radeon HD 6950 Board in Detail
Like its bigger brother, the Radeon HD 6950 still measures 27cm long (10.6 in), the typical length for today's high-end graphics cards. For example, the old Radeon HD 4870 X2 graphics card measures 28cm long, as does the more recent Radeon HD 5870. The Radeon HD 6950 is also the same length as the more expensive GeForce GTX 580 graphics card.
Just as its predecessor, the Radeon HD 6950 GPU has been fabricated using the 40nm process, yet AMD has squeezed in 486 million more transistors resulting in a die increase of 16%.
The GPU core is clocked at 800MHz, 9% lower than the Radeon HD 6970, while the GDDR5 memory also operates 9% slower at 1250MHz. Pairing that frequency with a 256-bit wide memory bus gives the Radeon HD 6950 a theoretical bandwidth of 160GB/s which, as you may have guessed, is 9% less than the HD 6970.
The Radeon HD 6950 also differs from the more expensive HD 6970 in its core configuration. Whereas the Radeon HD 6970 featured 1536 SPUs, 96 TAUs and 32 ROPs, the cut down HD 6950 packs 1408 SPUs, 88 TAUs, and the same 32 ROPs (8% less SPUs and TAUs).
Cooling the "Cayman Pro" GPU is a fairly large aluminum vapor chamber heatsink made up of 39 fins measuring 13.5cm long, 6.5cm wide, and 2.5cm tall. The vapor chamber design was first implemented in the Radeon HD 5970 and has recently also been adopted by Nvidia with their GeForce GTX 580 and GTX 570 graphics cards. Cooling the heatsink is a 75x20mm blower fan that draws air in from the case and pushes it out through the back.
For the most part, this fan operates very quietly, helped by the impressively low 20 watt idle consumption of the Radeon HD 6950. When gaming the fan will spin up as the card can consume up to 200 watts under load. This is ~6% more than the Radeon HD 5870, but even with the increased thermal stress, the fan didn't scream at intolerable levels.
The heatsink and fan have been enclosed within a custom-built housing that conceals the entire graphics card, a common practice for AMD when designing their most elite cards. We actually like this setup, as it helps protect the product very well. Nvidia has also done this in the past with their most prized graphics cards, such as the GeForce GTX 295 (dual GPU), though they have not used this design for their most recent flagship product, the GeForce GTX 580.
In order to feed the card enough power, AMD includes dual 6-pin PCI Express power connectors. This is the same setup used on the Radeon HD 5870, HD 6870 and GeForce GTX 580, GTX 570 graphics cards, so it's a configuration usually employed by high-end graphics cards.
Naturally, the Radeon HD 6950 supports Crossfire, so it has a pair of connectors to bridge two or more cards together. The only other connectors are on the I/O panel. Our AMD reference sample featured two dual DL-DVI connectors, a single HDMI 1.4a port, and two mini-DisplayPort 1.2 sockets.
It's worth noting that all Radeon HD 6950 graphics cards can support a max resolution of 2560x1600 on up to three monitors. With a multi-stream hub using the mini-DisplayPort 1.2 sockets, the card can power up to six monitors.