I have one running at 4.0 Ghz on the stock cooler, with a small increase in voltage (1.05 volts). I tried 4.0 Ghz at the stock voltage, but it was a little unstable. One tick up to 1.05V fixed it, and it has been rock solid since.
As a general guide to overclocking it:
http://www.anandtech.com/show/8232/...ary-edition-review-the-intel-pentium-g3258-ae
and from a post from another forum:
"batch number:341 8B990
at stock with auto settings it was running at just over 1v
i managed to get it up to 4ghz with the voltage manual set to 1v
4.2ghz needed 1.05v
4.4ghz needed 1.125v
4.6ghz needed 1.2v
4.8ghz needed 1.3v
4.911ghz needed 1.4v (which is what i am running it at normally)
5ghz isn't really bench stable on both cores but i can boot 5ghz on both cores ok and i can run super pi 1m@5.075ghz on 1.55v
my second pentium is not as good, i bought it about 10 days after the other one for £44 while it was on sale.
batch number: 341 9B312
at stock it was running on 1.086v, so i knew straight away that this wasn't going to be as good.
i manually set it to 1.2v and got 4.4ghz out of it.
4.5ghz needed 1.235v
it needs 1.3v to get to 4.6ghz which is 0.1v more than my other cpu which is a shame.
i got 4.7ghz bench stable at 1.4v and didn't bother going any higher because it wasn't as good as my other one. "
It is interesting that his 2 cpus ran at different stock voltages. I forget what my default voltage was, but I think it was 1.000 volts. So it looks like YMMV.