With ClockTweak I'm seemingly able to underlock my Radeon HD 6990's memory all the way down to 1 MHz. Reading back, the same value comes out. I kind of doubt that the hardware actually supports running at 1 MHz Commodore 64 speed though... And I don't seem to get any noticeable temperature drop either. So how do I find out how much I can REALLY underclock. MSI Afterburner let me go to only ca. 100 to 120 MHz below core speed (exact number depended on core speed), below that the display would show the stock 1250 MHz again. Still I got no temperature drop to speak of... and I've seen other people talk about underclocking to 300 MHz or even to 159 MHz.
My System: Windows 7 SP1 64-bit (fairly fresh installation but with all Windows Updates applied), Core2Quad 2.83 GHz, one HD 6990, Catalyst 11.6, Phoenix miner (SVN version 103) running from source on 64-bit Python 2.7.2.
I guess this should really go into the ClockTweak thread... but for now I'm restricted to this Newbie section.
Thank you for any help!