What affects hashrate? Core Clock or Mem Clock?

I have a XFX 290X and a Ref XFX 290 both hashing at ~60-65 H/s using Claymore 3.1 miner. I would like to overclock these cards and I tried playing with the Core Clock and Memory Clock settings but I didn't notice a change. I am using MSI AF and running Crimson 15.12 drivers.

Am I doing something wrong?

Thanks for your help!

mem clock does for my 380

I've noticed that if I push my cards past a certain point, the hashrate decreases.

Currently I have them both running at 1150 CC / 1100 Mem and my hashrate is 125-130 H/s

UPDATE: just started using Claymore v4, now I'm starting to see the difference in hashrate between the cards (maybe due to 290x is 8gb while ref 290 is 4gb?) but the 290x is now 90 H/s while the 290 is at 80-85 h/s giving me a total of 170-175 H/s

bump (20 characters..................................)

I want to know this too to decide what card to get cuz there is a lot of cards and viriants

470 8g
Or 480 4g or 480 8g