Well, I have a few friends with the Phenom II x4 965, and 1 of them got theirs stable at 4.2ghz, other can't get to 4ghz (Probably because its not C3) I seen a few people get to 4.4ghz on the 965, so it depends on the chip. the 965 should do at the vary least 4ghz, it might do lil higher.
And you would need a decent aftermarket cooler to get it there as well.
I've got a question about how much can you overclock the Phenom II X4 965 3.4 ghz Black Edition with Asus Sabertooth 990FX and the cpu heatsink is the
Coolermaster Vortex Plus.
I want to know how much i can overclock the Phenom II X4 965 with these components.
With the CPU cooler you are using probably 4ghz, that coolers limitations are the 4 heat pipes and the wide aluminum gap directly over the CPU Die, underneath the heat spreader, IMO cooler Master would had been better to have run 5 heat pipes so one would be directly over the center or a solid block contact.
Nevertheless since that is the cooling you are running load temperature will probably be your limiting factor since in my own testing I reached 4.3ghz stable on air cooling using a Xigmatek S1283 HDT cooler running 110cfm cooling fans.
Your thread title of How to overclock the Phenom II X4 965 and since it is a Black Edition CPU running an unlocked multiplier this should help you overclock it.