So I finally figured out how to change the bios so that you can decrease the lower bound of memory clock that aticonfig sees. By default, 58xx cards will only go down to 900Mhz. Here's how:
(Yes, you'll need windows to do this. Deal.)
1. Fire up
RBE and load up your stock bios. (I use
GPU-Z to copy it out of my cards)
2. Go to the Clock Settings tab.
3. In the Powerplay states struct list, click and hold on state 1.
4. 3 of the clock info settings will highlight in different colors, red, yellow and green. The yellow one is the one we want. 99% of the time it will be clock info 02, but this step is just to make sure.
5. Change the RAM setting from 900 to 300.
6. If you want to increase the upper bound for Core speed, go to the Additional features tab, and in the "Increase overdrive limit" section, choose method 2, and set the Upper limit GPU to whatever you want. For 5850s, I set mine to 950, just to give some headroom. WARNING: THIS MAY NOT WORK FOR YOUR CARD. For those of you with multigpu setups, flash a card that isn't your primary first to make sure it comes up okay.
7. reboot into linux and check your ranges with "aticonfig --odgc --adapter=all" ....you should see that you can underclock to 300.
8. Enjoy lower temps without decreasing your hashrate!
