Macbook CPU never throttles down to 1 GHz in OSX

[nermal0]

According to CoreDuoTemp, my Macbook 1.83 GHz Core Duo CPU runs either at 1.83 GHz (load) or 1.5 GHz (idle). Windows and Linux are able to throttle the CPU down to 1 GHz when idle, saving battery power and reducing the enormous heat.

Why doesn't OSX do that? Is CoreDuoTemp accurate? How can I make OSX throttle it to 1 GHz?

 

[DannySmurf]

According to CoreDuoTemp, my Macbook 1.83 GHz Core Duo CPU runs either at 1.83 GHz (load) or 1.5 GHz (idle). Windows and Linux are able to throttle the CPU down to 1 GHz when idle, saving battery power and reducing the enormous heat.

Why doesn't OSX do that? Is CoreDuoTemp accurate? How can I make OSX throttle it to 1 GHz?

How/how far the processor gets throttled is a function of the operating system's power management subsystem. The only way for you to "make" OSX do that is to hack some kernel files.

Out of curiosity, did you install any non-WindowsUpdate updates for Windows XP? My copy of XP runs MUCH hotter on my MBP, and I only get about 2/3 the battery life in Windows that I do in OSX.

 

[nermal0]

How/how far the processor gets throttled is a function of the operating system's power management subsystem. The only way for you to "make" OSX do that is to hack some kernel files.

I can't believe they "forgot" that feature... this is a major flaw in OSX. CPU throttling is one of the best and striking features of todays mobile CPUs, but that technology is useless when the OS doesn't enabled it...

Out of curiosity, did you install any non-WindowsUpdate updates for Windows XP? My copy of XP runs MUCH hotter on my MBP, and I only get about 2/3 the battery life in Windows that I do in OSX.

Windows is correctly throttling the CPU, so it consumes less power in XP. Maybe some other components draw more power in Windows? It could be HD spindown, screen brightness control, wireless and BT power management etc. that's missing there.

 

[thegreatluke]

I know this isn't the issue, but due to a manufacturing defect some MacBooks have been shipping with a thin film that blocks the vents on the inside of the hinge.

If you feel around for a little film, and you have it and pull it off, the vents will be open and your heat will decrease significantly.

 

[DannySmurf]

I can't believe they "forgot" that feature... this is a major flaw in OSX. CPU throttling is one of the best and striking features of todays mobile CPUs, but that technology is useless when the OS doesn't enabled it...

Does your CPU not throttle at all in OSX? Mine does, but it only goes down to 1.5GHz, not 1GHz.

I'm sure Apple did not "forget" to throttle the CPU all the way down to 1GHz; it was obviously an intentional decision. But they may have had a reason for only going as far down as 1.5. The OS may need it not to be any lower than 1.5. I personally can't think of any reason for that, but then I know nothing about OSX's internals.

 

[Cocoi]

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Windows is correctly throttling the CPU, so it consumes less power in XP. Maybe some other components draw more power in Windows? It could be HD spindown, screen brightness control, wireless and BT power management etc. that's missing there.

Well, maybe? The permanent optical audio enabled, the wireless fuction is often on only-on mode, bluetooth is rather tough to get rid of, the HD is more active (in my machine) and I guess it just has a lot of systems turned on. I am quite sure the Macbook runs down it's battery so fast because there are still some things to iron out before it's getting optimal performance in all fields on the MB - MBP.

 

[nermal0]

Does your CPU not throttle at all in OSX? Mine does, but it only goes down to 1.5GHz, not 1GHz.

Same here. I doesn't throttle down to the possible minimum. Bummer!

I'm sure Apple did not "forget" to throttle the CPU all the way down to 1GHz; it was obviously an intentional decision. But they may have had a reason for only going as far down as 1.5. The OS may need it not to be any lower than 1.5. I personally can't think of any reason for that, but then I know nothing about OSX's internals.

I also cannot think of any reason why they would intentionally do that. It works great for Windows and Linux, so why not for OSX? If they had implemented it, they could have bragged with even more battery life on the Macbook and they would receive less complaints about heat. I'm starting to miss my Linux... there all I did was: enable feature in kernel config -> recompile modules -> load modules -> works.

 

[Rovman]

I must admit, windows CPU throttling works far better than OSX's. It actually throttles right down to 1ghz with resonable increments upto the max of 1.83. OSX hoever sets it at 1.5 when not doing anything or 1.83 under load. Theres no stepping or inbetweens its, either 1.5 or max.

When i'm just browsing forums, 1ghz would be more than adequate. Hopefully Speedit will fix this (assuming apple doesn't decide to properly implement speedstep)

 

[zakatov]

When i'm just browsing forums, 1ghz would be more than adequate. Hopefully Speedit will fix this (assuming apple doesn't decide to properly implement speedstep)

I don't think 1ghz is enough even for web browsing. Not to diss Safari or any other OSX browsers, but they're not particularly efficient, especially with flash or java stuff. On my MBP the CPU goes from 1.5-2.17 Ghz in about .11Ghz incriments, so it's all good.

 

[DannySmurf]

especially with flash or java stuff

Well, that shouldn't be an issue. Flash or Java should kick the processor back up if it's needed. They're not static content, like an HTML page.

 

[thejadedmonkey]

1ghz min? Ha! I've seen my laptop drop down to 75mhz while it just sits there. Yes, that's <.1ghz. If XP can do it, I'm sure OS X can...I just think Apple has some bugs to iron out...

P.S. Generally it sits at 247mhz though, unless I'm making it think (ie more than word or internet)

 

[gekko513]

Does anyone know how much difference there is in power consumption between running at 1.5GHz and 1GHz for the Core Duo? Maybe it doesn't really make much difference and that's why OS X doesn't throttle it further down.

If Windows gets shorter battery life, then OS X clearly does a better job of managing the power, so it doesn't seem like much advantage of going down to 1GHz as Windows seems to do.

 

[brbubba]

OSX hoever sets it at 1.5 when not doing anything or 1.83 under load. Theres no stepping or inbetweens its, either 1.5 or max.

Me too except its either 1.5 or 2.0. Once in a while it hits 1.83 briefly. ANd I have seen it do 1.33 twice, and both times it was for one second.

 

[nermal0]

Maybe it doesn't really make much difference and that's why OS X doesn't throttle it further down.

Even if it would just make a tiny difference of one or two watts in power consumption or 10 minutes in battery life, there is really no reason I can see for Apple not to implement it.
The fans on my Macbook kick in very late, usually when the temperature is already above 70°C. What happens is that the CPU heats up fast, but the late fans can't catch up in time, so the CPU reaches more than 80°C and starts throttling to prevent itself from overheating. This protection mechanism sometimes sets my clock speed to 1.33 GHz for a second. This never happens when idling. Thanks to the late fans and the 1.5 GHz in idle mode, my CPU never cools down below 60°C. I could fry eggs on the Macbooks bottom side.