Why is there a base fan speed?

[poiihy]

The old ibooks etc had fans that only spun up when it get hot, but stayed off most of the time. Why do the new macs have fans that always run at a base speed, especially the portables? It would reduce battery life too. Why doesn't it just spin up when it needs to?

 

[aristobrat]

The old ibooks etc had fans that only spun up when it get hot, but stayed off most of the time. Why do the new macs have fans that always run at a base speed, especially the portables? It would reduce battery life too. Why doesn't it just spin up when it needs to?

Hmm, I'm not sure how far back you're talking about when you say "new Macs", but I remember using SMCFanControl (to bump up the base fan speed) on the first generation MacBook Pros and MacBooks, which came out 9 years ago.

Maybe the Intel processors make more heat than the old PowerPC processors that were used in the iBooks.

 

[poiihy]

Hmm, I'm not sure how far back you're talking about when you say "new Macs", but I remember using SMCFanControl (to bump up the base fan speed) on the first generation MacBook Pros and MacBooks, which came out 9 years ago.

Maybe the Intel processors make more heat than the old PowerPC processors that were used in the iBooks.

Even if they do make more heat then Intel processors, can't they follow their sensors rather than stay at the base speed?

Hmm..... maybe the fans can't run at such low speeds. But then how did PPC fans do it? maybe their fans were bigger

 

[freeskier93]

It's pretty simple really, those chips weren't near as powerful. Those PowerPC chips had TDPs under 20 watts. By comparison the C2D in my 2010 MPB has a 65 watt TDP. We're really only just getting back down to low TDPs. The i5 used in the MBA is 15 watts. Times are very different though, performance expectants are very different. Back then you could get away with throttling the CPU down to a point where the fan could turn off.

 

[simonsi]

The old ibooks etc had fans that only spun up when it get hot, but stayed off most of the time. Why do the new macs have fans that always run at a base speed, especially the portables? It would reduce battery life too. Why doesn't it just spin up when it needs to?

Probably because without the fans running there will be stagnant air and the sensors won't read accurately.

 

[dusk007]

A lot of windows notebooks turn off the fans completely when heat allows. Apple just has really quiet fans that are almost inaudible at 2000rpm so there is no real gain in turning them of. Some of the cheaper windows notebooks also have cheaper fans that show a significant difference when off.

An HDD is a lot louder than those 2000rpm fans and now with ssds you need a really quiet environment to make out the fans at all and even then they are far from annoyingly loud.

 

[ha1o2surfer]

It's pretty simple really, those chips weren't near as powerful. Those PowerPC chips had TDPs under 20 watts. By comparison the C2D in my 2010 MPB has a 65 watt TDP. We're really only just getting back down to low TDPs. The i5 used in the MBA is 15 watts. Times are very different though, performance expectants are very different. Back then you could get away with throttling the CPU down to a point where the fan could turn off.

There are no mobile CPU's that have a TDP of 65 watts. lol Unless it's overclocked.

 

[freeskier93]

Whoops, yeah 65 watts is desktop. Mobile is 35 watts. Point still stands though.

 

[poiihy]

It's pretty simple really, those chips weren't near as powerful. Those PowerPC chips had TDPs under 20 watts. By comparison the C2D in my 2010 MPB has a 65 watt TDP. We're really only just getting back down to low TDPs. The i5 used in the MBA is 15 watts. Times are very different though, performance expectants are very different. Back then you could get away with throttling the CPU down to a point where the fan could turn off.

Even if they did make more heat, they still can just follow the sensors (function as if base speed was 0).

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A lot of windows notebooks turn off the fans completely when heat allows. Apple just has really quiet fans that are almost inaudible at 2000rpm so there is no real gain in turning them of. Some of the cheaper windows notebooks also have cheaper fans that show a significant difference when off.

An HDD is a lot louder than those 2000rpm fans and now with ssds you need a really quiet environment to make out the fans at all and even then they are far from annoyingly loud.

They still consume power and reduce battery life.
I would think the MacBook Airs not have a base speed at least.