Not sure about this. I just picked one up. I was running an E2140 OC'd @2.66 MHz. I am hoping to hit high 3 or low 4 with this chip.
I had an E2180 before this, and I overclocked it to 2.2 GHz with stock voltages. I have already boosted this to 3.7 on stock voltages, but I stopped because I was happy with it. I'm sure I can get to at least 4, but my cooling likely isn't adequate for that.