The Radeon HD 2900 XT Card

Chances are you’ve probably seen some of the shots of the Radeon HD 2900 XT by now, the first images of prototype engineering sample boards leaked on the web late last year. As you can see, the final retail board design looks identical to those prototype boards, with AMD utilizing a large dual-slot cooler for keeping the graphics core, memory, and many board-level components cool.

There were rumors swirling of multiple Radeon HD 2900 SKUs in development: a Radeon HD 2900 XT like the card you see today, a 9.5” Radeon HD 2900 XTX card intended for the retail market, and a OEM variant of the XTX which featured a 11.5” PCB and slightly different cooler. Ultimately though only one SKU is being released today – the Radeon HD 2900 XT.

AMD won’t confirm if they have any plans to eventually release an XTX model; assuming an XTX model was in the works for release early this summer we prodded multiple representatives from ATI on this issue and we consistently got a negative response, suggesting that if AMD does plan to eventually reveal a Radeon HD 2900 XTX SKU with faster clocks it isn’t due for release in the immediate future. Our guess is we won’t see an ultra high-end $500+ SKU until R600 transitions to TSMC’s smaller, less power-hungry 65-nm manufacturing process.

Power delivery

Another aspect that’s been discussed repeatedly on numerous forums across the web relates to the Radeon HD 2900 XT’s power draw. These rumors were fueled largely because of the card’s unique 8-pin power connector. Located in the upper right corner you’ll immediately spot the 6-pin PCI Express power connector that’s become standard fare on most high-end graphics cards, however sitting alongside it is a larger 8-pin power connector.

This second, 8-pin power connector is required in order for the card to operate, but fortunately it’s backward-compatible with today’s existing power supplies, many of which only have 6-pin PCIe connectors. You can see how it’s been designed to operate in the following image:


Now you’re probably wondering why AMD integrated an 8-pin power connector on the Radeon HD 2900 XT if the card can run off all of today’s existing power supplies, many of which only have 6-pin PCIe connectors. The 8-pin power connector is only required for overclocking.

You see, the Radeon HD 2900 XT’s maximum TDP at stock speeds is 215 watts (in comparison, the max TDP for GeForce 8800 GTX is 185 watts). Each auxiliary 6-pin PCIe power connector can run up to 75W, and the PCIe interface itself maxes out at 75W. With all three connections, that’s 225 watts – just enough power to get by at stock speeds. That’s not enough power for someone who may be overclocking their card however. This is where the 8-pin power connector comes in.

The 8-pin power connector alone can carry up to 150 watts. When combined with the 75W from the PCIe interface and the 75 watts from the 6-pin PCIe power connector, up to 300W can be fed to the Radeon HD 2900 XT. We conducted power consumption tests later in this article that you’ll want to check out, but to make a long story short, you won’t need a PSU with an 8-pin power connector unless you want to overclock the graphics card.

In order to overclock the card, you must plug in the 8-pin power connector and the 6-pin power connector, otherwise the driver automatically disables all overclocking.

In terms of power supply guidelines, AMD recommends a minimum of a 550W power supply for single card Radeon HD 2900 XT configurations, and a 750W PSU if you plan on running CrossFire.