my e6750 is stable on my gigabyte ds3 at 3.4 @ 1.44 volts, max temp hits 65c under prime95 (but never above 60 during normal games). i have tried several times to get to 3.5. to do this i have to up the vcore to 1.49 (max is 1.5 for my core 2 duo 65nm). i ran 3.5 stable for 6 hours under prime95 at this vcore, temp his 68c one time after about 3 hours, but otherwise it stayed 64-65c.
well it IS stable, but the vcore is awfully high, and 68c, while it would never get that hot during normal operation), is still pretty hot even if it hits it for one second. so my question is whether or not that's a safe OC, or if the more manageable and mentally relieving 3.4 @ 1.44 is better to stick with?
honestly the changes i saw were from a 14,600 3dmark06 score to a 14,800 score, so not a huge change for a 100mhz OC, especially if i am getting to that point where it might be stable but just too close to being TOO hot or given TOO much juice to run for everyday 24/7 applications.
As you pointed out, 100MHz isn't worth the extra voltage/heat. Your better off staying at 3.4. I'd start to look at the ram next. You might be able to tweak things so that you get a bit more performance out of it that way. From what I know 3.4GHz is normal for the 65nm C2D. If you had one of the 45nm C2D (8x00) then you should be able to get to around 4GHz.