EIST and C1E sure appear to be the same thing, but they are not.

EIST handles the FID (Frequency ID) of the CPU, which means it's responsible for lowering and increasing the CPU frequency on-demand or by software request. Also, keep in mind that you EIST might still be enabled when you select a FID on the BIOS. You might just be selecting the MAXIMUM FID available for the CPU, not locking it.

CxE handles the VID (Voltage ID) of the CPU, which means it's responsible for controlling the CPU voltage, especially if the CPU enters idle mode. Also, CxE handles the enhanced power savings modes of the CPU. It may just be lowering the VID when the CPU is idle and at minimum FID (C1E) on desktop CPUs, all the way to lowering the FSB and voltage, along with an enhanced CPU power-down (Hard C4E), on some T7x00 and Penryn mobile CPUs.

The TM Function does in fact handle the CPU throttling (and shut down) when it's overheating (though you can force those states through software, too). If I remember correctly, TM1 is embedded on all socket 775 CPUs and can't be disabled; TM2 (enhanced version, which not only forces throttling but also a CPU VID and FID) can be disabled, though it's usually enabled. Since they are preventive measures, and don't kick in unless REALLY necessary, I'd advise you not to mess with TM, unless if you want to set a lower default VID/FID for TM2, which could be beneficial.

As for PEG Link, I never had any problems with that, even on fast settings, other than an occasional system hang. I've also not seen any noticeable performance boosts when using it, though...

Cheers.

Miguel