I have found that W7 Aero desktop does suck around 100khs on a 2560x1600 resolution with a dual link DVI. This system has 2x7970s and the GPU having monitor connected to is doing only ~600khs while the other GPU does +700khs.
My completely headless miner does 740khs on all cards. Gigabyte Windforce 3 OC 7970 (GV-R797OC-3GD) rev 2.1 volt locked cards here @ 1060/1460.
cgminer 2.11.4 --scrypt --lookup-gap 2 -I 13 -w 256 -g 2 --thread-concurrency 8192
Catalyst 13.1
Thanks to your post BBQKorv, I adjusted my settings a bit (added lookup-gap 2 and bumped core up to 1060) and now getting a bit closer to your results, ~ 725khs.
Do you think going from the 12.1 driver to the 13.1 will get me the other 15khs? Anyone else have trouble with buggy installation of the 13.1's like I did?
Thanks
cgminer version 2.11.4 - Started: [2013-04-14 08:40:42]
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(5s):724.9K (avg):724.2Kh/s | A:1272 R:4 HW:0 U:5.1/m WU:690.5/m
ST: 5 SS: 0 NB: 111 LW: 2322 GF: 0 RF: 0
Connected to us.wemineltc.com diff 209 with stratum as user XXXXX
Block: 9146cb525115b6d7... Diff:19.2M Started: [12:47:19] Best share: 262K
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[P]ool management [G]PU management [ S]ettings [D]isplay options [Q]uit
GPU 0: 72.0C 3346RPM | 726.8K/724.2Kh/s | A:1272 R:4 HW:0 U: 5.07/m I:13
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Also for the last poster, the reason I went for the 7970 over the 7950 is I will occasionally use it for gaming. I do not have a dedicated mining rig, yet.