2600 MHz? Did you checked for memory errors? I am sure there will be plenty.
I have been running stable @ 2300 memory as well as 1425 on core mining ETH, ZEC as well as XMR over a 24+ hour period. I haven't tested for memory errors but remain convinced I haven't encountered any given I haven't been submitting an excessive number of stale/invalid/incorrect shares. I'm simply waiting for another member to confirm it is indeed safe to go beyond that threshold.