The secret of the AMD 6900’s second switch

Forget NDA’s, we never liked them anyway

ATI Radeon logoAT SEMIACCURATE WE never met an NDA we did like and most sites seem to ignore them on a whim to whore views, so now seems as good a time as any to violate a few about the AMD 6900 series. We don’t want to feel like loners. Some of the card’s secrets have leaked by now, but the biggest one, the second switch, hasn’t even made the speculation circuit yet.

Our excuse for violating the NDA is simple, I had Thai food for dinner, and it didn’t agree with me. Between that and running out of ice cream, I was downright peeved, so fsck the man! Here is the NDA busting secret of the second switch on the 6900 series GPUs.

As everyone out there knows, the first switch changes the color of the LEDs in the fan. You can set it to a single color or have it cycle through 7 colors. You just need to toggle the color or colors with that switch within 25 seconds of power up. Colors are input in binary RGB-32 format.

The second switch itself is cleverly hidden on the back of the card, and you can see it is tiny and almost unnoticeable. It measures a mere 2.5 inches in length by just over an inch in height, and it is cleverly camouflaged against the black back plate. Most people missed it in the pictures, but if you know what to look for, you can spot it quite easily.

6900 second switch

Look closely, you can see it to the left of the GPU

What does it do? Easy enough, it swaps the shader count. The ‘normal’ count is 1920 for a 205W 6970 card, and the switch opens up the full force of all 2520 shaders. The reason this switch is set to ‘low’ is that between the clock speed advances, 730MHz/1920 shaders to 920MHz/2520 shaders, it blows the card through the 300W cap for PCIe cards.

This switch is an elegant way of going from sub-GTX570 performance to way way way over GTX580 performance, and still getting PCIe certification. Very slick guys, well done. If you don’t have the right drivers though, the switch does basically nothing, which is why those who bough the card retail haven’t seen the results they think they should get.

One last bit of NDA bursting, our tester Max Cowgill was asked about what flavor the card was. From his ice fortress, basically the snowbank where his VW Rabbit pickup got stuck in the weekend’s blizzard, replied, “Cherry with licorice stripes”. We concur, as do our ‘reliable’ sources.S|A

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Update: Typ0 – 5970 -> 6970

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Charlie Demerjian

Roving engine of chaos and snide remarks at SemiAccurate
Charlie Demerjian is the founder of Stone Arch Networking Services and is a technology news site; addressing hardware design, software selection, customization, securing and maintenance, with over one million views per month. He is a technologist and analyst specializing in semiconductors, system and network architecture. As head writer of, he regularly advises writers, analysts, and industry executives on technical matters and long lead industry trends. Charlie is also available through Guidepoint and Mosaic. FullyAccurate