IIRC, once AMD became aware of this issue, they started releasing a new BIOS that made the whole 4th core thing impossible. For stability reasons I guess. That's why changing ACC to auto isn't doing anything for you.
Why don't you PMing anyone who's managed to do it on the original thread?
From my understanding, unlocking a 4th core was only achieved on the 790GX chipset, not the 790X. Interesting you managed to do it. But, is it stable???
Only difference between the GX and X chipset is the lack of onboard video so I doubt the HD3300 would affect enabling the 4th core.
Bad news is that the 4th core is not stable with the F2B bios on this AM3 motherboard. I don't know what's wrong really. My previous AM2+ Asrock AOD790GX/128M motherboard ran perfectly fine with the 4th core enabled. I was able to push the 4x cores to a staggering 3.5ghz with just 1.40v. I suspect an immature "beta" bios but I'm not sure.
I that sucks. I think the only AM3 board that can unlock the phenom 2s is the ASRock M3A790GXH/128M. I searched and searched all over the net for an am3 board that would and that was the only verified board i could find. I ordered one myself but it wont be here till wednesday to check my 720. I may be wrong but I dont think your board is ever gonna support it as AMD has told all their motherboard manufactures to not allow this anymore. They are making these boards under AMD licenses and to specs so its not likely they would want to go against their call. So there are still older bios versions that are available that allow this. The am2+ have many more board options that can do it. As for am3, which came right as AMD was pushing the stop button, there isnt much if any. But i did find that AM3 asrock above menchioned still can unlock with the original released bios which is still available for download at their site. Its probably not gonna be installed on any board that has left asrock in the last 2 months but you can flash it. Here is the 2nd page from what evongugg post. It also verifies the asrock am3 http://www.tomshardware.com/reviews/unlock-phenom-ii,22...
So I couldnt find any other am3 board verified posted or reported anywhere on the net. And i looked for hours. So if you or anyone else can verify another am3 board that will unlock phenom2s then please do let me know