Enable Speed Step, but disable Turbo Boost?

[wamatt]

Adam, was wondering if it's possible to prevent the processor from going above it's native clock, ...but still allow it to go below, (using speed step), when it's not doing heavy work.

For example. I have an i7 2760QM that's natively clocked at 2.4ghz. It will boost to around 3.6 and go down to 0.8 depending on the load. However if I run DisableTurboBoost, then Speed Step is also removed and the clock is locked to 2.4ghz.

[nanoant]

@wamatt I don't think I can do much about it. TurboBoost is single bit in MSR register (according to Intel docs), so if it disables Speed Step too you cannot have one without the another.

All I can recommend you is using Fan Control. I use it on my MBP (but older one) and it does very good job cooling it down, since on default settings it just runs too hot.

[wamatt]

thanks for the suggestiong @nanoant. yeah I use the Apple smc from the command line to control fans. eg,

$ smc -k F0Mx -w 3800 && smc -k F1Mx -w 3800)

works nicely (since Fan Control itself seemed buggy on the new MBP with ML). So while SMC in addition to CoolBook (http://www.coolbook.se/) worked well on my old MBP core duo, however on the i5/i7 undervolting (aka software regulated voltage changes) are not possible. Which is a real pity, since undervolting works really well to bring down wattage.

Now moving on... if I use the Power Gadget tool from Intel, http://software.intel.com/en-us/articles/intel-power-gadget-20, it does a decent job reporting on the current frequency.

Now the thing is, when I'm using the laptop normally Speed Step works fine and browsing etc usually means the CPU is around 1.5-2ghz clock. However, closing the lid and plugging in an external Thunderbolt display, causes the CPU to kick into constant Turbo Boost mode, IOW it runs the CPU between 3-3.6GHZ

This in turn causes the total wattage to increase and temperatures, which in turns spins fans louder. So the overall effect of all this is, it's not actually possible to limit the fans to <3500 whilst in clamshell mode. If I do, then a runaway thermal process occurs, and the OS then does a forced throttle for 1minute down to 0.8GHZ, making everything painful to use.

Not sure, if you can add anything, just had to get that out there. So even with disabling turbo-boost the situation is better in clamshell (since it doesnt go up to 3.6ghz constantly or whatever), but it doesn't drop down below 2.4ghz either.

[jameswald]

Perhaps another service could monitor the processor load and temperatures and enable DisableTurboBoost only when needed. This might allow speed stepping to continue to save energy while the CPU is mostly idle.