So basically in April last year I got a PC with:
AMD FX4100 @ 4.0ghz
ATI Radeon 6770
8gb RAM (1333 methinks)
M5A78L-M LX V2 Motherboard
And, a couple of months ago I bought Borderlands 2, and had to update my BIOS to get it to work. I noticed after I was done that my processor went down to 3.6ghz, and I want to know THE VERY SIMPLEST way of overlcoking it to 3.9/4.0ghz again.
First off, im no pro to this but this is how i increased my Frequency about 300Mhz.
And sorry if this is not simple enough but as i say i dont know any other method as of now.
I'm not sure exactly but, I have a similar motherboard to you and the multiplier is locked so you have to do it by increasing the FSB. However it may be the CPU that doesnt allow the multiplier change not the mobo, im not too sure.
But anyway, if the multiplier is locked then you should get some programs such as CPU-Z, HW Monitor and Prime 95.
Check CPU-Z to see what your voltage (Vcore) is and make sure that you dont go too high over that so your CPU doesnt become too unstable.
Then change your FSB up a few notches in your BIOS nothing too drastic in case your voltage shoots up, if your voltage does jump up too high then change the setting in the BIOS from auto to something near your Stock voltage. Check in CPU-Z what your Core clock is now and it might be what you want 3.9Ghz-ish or it may be below, even if it is still abit low run some tests in Prime-95 and see what you core temperatures reach in HW Monitor to check its stability.
If all is stable then increase the FSB in BIOS again if you still not happy with the fequency, and then check stability and temps again.
A few things to note is make sure that your Memory Frequency doesn't get too high (check CPU-Z) it shouldnt get too high above stock value, if it does just bring it down in BIOS, also you dont want your HT-link (also check CPU-Z) to get too high above stock, again if it does bring it down in your BIOS.
Hope this helps, sorry again if its not what you were after.