Alright. Main post has been updated, with new regulations limiting core clock to 100 MHz or 20%, whichever is lower, above reference stock. That seemed a fair way to limit clocks that could be applied to any card, wouldn't allow insane overclocks, and requires no judgement on my part. As always, suggestions, corrections, etc. are always welcome.
The smaller of +100Mhz or +20% is +100Mhz in
all cases, you would need core clock under 500MHz for the 20% rule to take effect. "Running stable for 24 hrs" etc doesn't matter because these are easy overclocks, you just want to run the miner until it has results at least xxx.xMhash/s stable accuracy.
Note that running a lower GPU core overclock for benchmarking will also affect the "sweet spot" for memory underclock on 2.1-2.5 SDKs. My own research shows that changing a 5770 from 1000->850MHz will change the best memory speed from 295MHz to 270Mhz. This is important to note both for this competition, and for trying these results on your own miner when you want to go back to maximum overclock.
Here are the official AMD stock core clocks of common mining GPUs, and their "competition" overclock of +100Mhz (which is significantly lower than typically attainable, but should be achievable by all [except perhaps 7970 @ 1025MHz]):
Model | Shaders | Stock MHz | Overclock |
5770 | 800 | 850 | 950 |
5830 | 1120 | 800 | 900 |
5850 | 1440 | 725 | 825 |
5870 | 1600 | 850 | 950 |
5970 | 3200 | 725 | 825 |
|
Model | Shaders | Stock | Overclock |
6850 | 960 | 775 | 875 |
6870 | 1120 | 900 | 1000 |
6950 | 1408 | 800 | 900 |
6970 | 1536 | 880 | 980 |
6990 | 3072 | 830 | 930 |
|
Model | Shaders | Stock | Overclock |
7950 | 1792 | 800 | 900 |
7970 | 2048 | 925 | 1025 |
(Note the table above highlights the numbering sham that is the 6xxx series; a 5830 gets about the same hashrate as a 6870 when pushed to the similar max overclock, as they have the same number of vertex shader cores.)