This Litecoin mining is less a Science at this point than it seems to be Sorcery.
I had to completely and radically change the cgminer settings to get the same performance from this card on a riser in the 3rd slot.
Why on earth would two identical cards require wildly different settings in different slots on the same motherboard but in the end perform the same? I think there is a LOT better performance that could be had from GPUs in scrypt mining - this inconsistency shows unoptimized and possibly buggy software imho. (at least on RADEON 79XX).
I agree, there are sweet spots that you can find though.
For instance at 950 core I get the same performance on a 7970 at mem speed 1225 and 1425. If scrypt is all about memory speed then that makes no damn sense. Everywhere between 1225 and 1425 mhz is very bad KHs.
I think the 7 series cards might have a lot of power hidden in the. But then if someone writes a better miner why would they release it?