UPDATE: It's quite possible that disabling Speedstep is overkill. I'm having success re-enabling Speedstep and disabling CORE PARKING.
After putting in some hours last night, I'm fairly confident that the problem with Skyrim rebooting my system is solved by disabling Intel Speedstep. No issues whatsoever running Skyrim. Naturally, since the idea behind Speedstep is to lower the power consumption, it stands to reason that increased power consumption and increased heat would be a concern. I can't do anything about the power consumption, but I should really worry about the heat. To that end, here are some charts I put together that hopefully will help add to the discussion regarding Skyrim reboots and the effects of disabling Speedstep.
To disable Speedstep, go into your BIOS and disable the following "Advanced CPU" Core Features:
CPU Enhanced Halt (C1E)
C3/C6 State Support
CPU EIST Function
The following charts demonstrate the effect on CPU frequency and voltage when Speedstep is enabled and disabled:
|CPU Frequency and Voltage under load with Speedstep ENABLED|
|CPU Frequency and Voltage under load with Speedstep DISABLED|
|CPU/GPU Temperatures under load with Speedstep ENABLED|
|CPU/GPU Temperatures under load with Speedstep DISABLED|
The data show that with Speedstep enabled, we get slightly lower CPU temperatures in the cores never going beyond 60C and possibly slightly lower CPU loads (this probably needs a more controlled test to confirm). After Speedstep is disabled, we see core temperatures getting closer to 70C, still below the danger zones, although getting really close to it. It's still not clear what the temperature max is for the 2600K, but Intel's specs show a "TCase" of 72.6C, which probably doesn't mean as much as the TJMax, which, if I read the Core MSRs on my CPU properly, comes out to 01100010 or 0x62 or 98C:
MSR 0x000001A2 0x00000000 0x00621200
I'm looking at this as the temperature at which the CPU will call it quits. With a 20% buffer, I think I am comfortably outside the overheating temperature zone for this CPU.
Presumably the power consumption goes up with Speedstep disabled, but I have no measuring tools for that. HWInfo64 does report that the +12V at a steady 12.025V - 12.074V. Note: with my old no-name PSU, it varied between 11.436V and 11.976V.
So far so good. I hope this helps someone out there.