the core overclocks in 27mhz increments as well as far as i understand. also lots of you are comparing overclocks, but keep in mind that to claim that your overclock is stable you have to run things like furmark and atitool for quiete a long time (i would say an hour or 2, and if you're watercooling gpu and cpu in one loop run prime95 in parallel and check your temps then, otherwise you cant be sure your system is stable and can handle the heat when you actially run it).