GTL voltages are the singaling voltages for the type of FSB Intel uses. 65nm chips tend to like this voltage to be around 67% of the vcore, while the 45nm chips prefer 61-63%. there is a good bit of variation so playing around with settings near that can be helpful.
61% was noticeably better on both of my E8400s than 63%.
Originally Posted by RussianGrimmReaper
Intel states that anything over 1.45v(through the CPU, not in BIOS) will damage it. 1.365v is normal operating voltage.
1.45v is the absolute limit, and voltages between 1.3625v and 1.45v (at least at common temperatures) are very likely to damage the chip, according to Intel.
If you set you voltage to 1.45v in the bios, surges when coming off loads are sure to reach, or exceed this voltage slightly, even with a working vdroop.
If you remove vdroop, you can shoot way past the absolute limit, even if you have the voltage set around ~1.4v.