I'm currently running 2 Gigabyte Radeon HD 7950's and I have an issue with temperature in the upper tier card. The lower card can run at max speed (about 630 MH/s) and never touch 80°C but the upper card will blast over 80° (and even 90° if I let it) at much lower settings.
I've tried various cgminer configs and have my memclock down as low as it will go in MSI (though I haven't managed to get it to reduce lower by closing and re-opening MSI as some have suggested). The only way I've found to keep the upper card stable and around 80°C is to set the Power Limit % to -15 on that card. That seems to do the trick, but of course runs the card at ~300 MH/s.
My questions is: Until I get a better cooling system for the upper card (which is on order), am I doing any damage to the card by running it at -15% power? Insticntively it seems like that should be okay, but I thought I'd run it by your folks in case I'm missing something.
All the card is doing is clocking itself down - the 300Mhash isn't due to reduced power - its the reduced clocks. Run at lower speeds where you can keep it below 85.
Personally I run at 1085/1500 and -20 power, doesn't seem to affect me, still 88 degrees though! :S