AMD Radeon HD 6790 Review - PAGE 2

Visually the reference HD 6790 is identical to its older sibling the HD 6870, as both use same dual-bay heatsink shroud that measures 9.5 inches in length. They also both utilize the same black and red color scheme and include a large blower style fan at the end of the PCB. However, where the two cards differ are the internal specifications of the Barts based graphics processor. Additionally, even though the reference board resembles the HD 6870, AMD's AIB partners are going to be releasing their own custom designs, so its unlikely that the boards on the market will look like our sample.

The HD 6790 uses the new Barts LE GPU, which like is predecessor is built on a 40nm process that packs in 1.7 billion transistors and has a die size of 255 mm². Also since the core is Barts based it uses AMD's VLIW 5 Shader architecture. The GPU comes clocked at 840MHz and includes 800 Stream processors and 96 texture units, giving it a total compute power of 1.34 TFLOPs. In addition, the HD 6790 also includes a 1GB GDDR5 frame buffer that comes clocked at 1050MHz (4.2Gb/sec effective) and runs on a 256-bit interface.With these specifications the HD 6970 is positioned between the HD 5770 and HD 6850 in terms of performance.

The back panel of the HD 6790 is also identical to the HD 6870. From this angle you can see that the HD 6790 includes dual 6-pin power connectors, is equipped with eight memory chips that surround the GPU in a L shape, and that there is only a single CrossFire connection. As with the HD 6870, you can see that the VRM on the HD 6790 is located in front of the GPU, which puts it closer to the exhaust port. This can help reduce the GPU temperature by reducing the hot air that is pushed through the GPU as it is exhausted out of the card.

The HD 6790 includes a single CrossFire connection point, so this card will include 2-way CrossFire support. The nice thing here is that the HD 6790 can be linked with any other Barts based graphics card, so you can essentially CrossFire the HD 6790 with either a HD 6850 or HD 6870 for improved gaming performance. Of course there will be some reduced performance as we are scaling a lower-end card with a higher-end model, but there should still be a boost in performance compared to a single card setup.

The specification that surprised us the most was the HD 6970's TDP of 150W. That is high for an entry-level graphics card, as most graphics cards in this performance range tend to have a TDP under 150W, requiring only a single 6-pin connection for power. The HD 6790, however, has needs dual 75W 6-pin PCIe power connectors and also requires a power supply with a minimum rating of 500W. The idle power rating, however, is quite good as the board only consumes 19W of power at times of low use.

Also, AMD has brought to our attention that their AIB partners will use custom designed PCB, power connectors, cooler designs. The keyword here is power connectors. According to AMD, the power connection configuration is entirely up to the board partners, so there should be models hitting the market that may only use a single 6-pin power connector.

The rear video outputs on the HD 6790 are the same as those found on other Barts and Cayman based graphics cards. These includes a single HDMI 1.4a port, two Mini DisplayPorts, one SingleLink-DVI port, and a DL-DVI port. Like the other cards in the series, the Mini-DisplayPorts use the 1.2 standard, giving them a higher bandwidth and refresh rate, allowing each port to support Stereoscopic 3D, A/V and even multiple displays through a single port. The HDMI port is also updated to support the latest technologies, as the 1.4a connection now adds support for stereophonic 3D with AMD's HD3D Technology.

The Sapphire graphics card we are also looking at in this review shares the same video outputs as the reference model. However, AMD's AIB partners are able to configure their graphics cards output configurations, so there will be various options available at launch.