That can't be your problem. Both of mine say 63 cores in the log. I never checked this day one but I am running 796 clock and hashing at about 4.45 or so per stick.
jstefanop, 0-63 = 64 cores? You sure you did not mean to say 63 not 64 for the log output? Hard to believe both mine are exactly 63 cores in the log?
Everything is answered in this thread
Yes the printout is 63, it counts from 0. The normal hashrate = 5.66*clockspeed (page 1), meaning that 796Mhz gives ca 4.5Mh/s, which is what you get and there is no miracle in it.
Much lower than expected hashrates, very often somewhere between 2-2.5Mh/s can in many cases be traced back to power-supply issues. jstephanop has some theories on exactly what happens in the ASIC (somewhere in this thread). Out of personal experience, I would say that from 800Mhz and up you just have to try and play play with the hub and pot settings and temperature to find a good and above all
stable setup. As I wrote earlier, I have a whole bunch running at 924Mhz and some others at 856Mhz or something like it, but it took me while to get it exactly there. 796 was a piece of cake.