Waco wrote:Perhaps, but even with limited TDP a full-fat leaky 2600K/3770K/4770K is going to use more power than the S or T variants at similar performance levels.
This is at least only the case when the -S/-T chip is a dual core, as those chips are cooler.
Intel chips really have four modes of operation in this regard:
1) Guaranteed speed - traditional mode where the OS asks the CPU for a specific speed and the chip gives you that speed (3770K = 3.5GHz)
2) Turbo speed, frequency limited - no clock speed guarantee to OS, but we are below the power limit and at the max ratio limit
3) Turbo speed, power limited - no clock speed guarantee to OS, but we are at the power limit and must run below the max ratio limit. Note that the CPU frequency will never drop below the guaranteed speed, even if this results in TDP violations (ie. via power virus)
4) Power limit with clamping enabled - this is nonstandard operation. Enabling the clamping bit allows the CPU to go below the guaranteed frequency to hit power targets. This is nonstandard, I think, because power states no longer have any meaning for the OS (ie. no longer a guaranteed frequency).
Adjusting the max non-turbo ratio is the way the S/T chips do it, as they have very low guaranteed frequencies which essentially cannot exceed the specified TDP even under power virus conditions. The way S/T chips are implemented can be simulated via programming the max non-turbo ratio (it's a CPU MSR) to a specific low value, and using turbo mode to control power consumption. Not sure you need a K-series chip but it may be necessary.
I've done this (setting the max non-turbo ratio to 12x) on my 3720QM before to try going below 36W, but it didn't work.