# How, exactly does a CPU generate heat? **URL:** \ **Category:** Factual Questions\ **Created:** [December 18, 2013, 3:45pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652 "2013-12-18T15:45:02Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Jake](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@Jake](https://boards.straightdope.com/u/Jake)\ **Post date:** [December 18, 2013, 3:45pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/1 "2013-12-18T15:45:02Z")
There are not any moving parts (As far as I know), no filaments to heat up… yet it requires heat sinks, fans and stuff like that. Anybody? 😕 ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [December 18, 2013, 3:49pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/2 "2013-12-18T15:49:15Z")
[Resistance](http://en.wikipedia.org/wiki/Electrical_resistance). There’s a lot of it. ---
**Author:** ![Jake](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@Jake](https://boards.straightdope.com/u/Jake)\ **Post date:** [December 18, 2013, 3:51pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/3 "2013-12-18T15:51:46Z")
Hmm… Yeah. I shoulda thought of that! Thanks ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [December 18, 2013, 4:30pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/4 "2013-12-18T16:30:41Z")
They’re called semiconductors for a reason. ---
**Author:** ![DrCube](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@DrCube](https://boards.straightdope.com/u/DrCube)\ **Post date:** [December 18, 2013, 5:09pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/5 "2013-12-18T17:09:01Z")
How exactly does your toaster generate heat? ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [December 18, 2013, 5:28pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/6 "2013-12-18T17:28:31Z")
> [@DrCube](#): > > How exactly does your toaster generate heat? You’re thinking of an [artificially intelligent](http://reddwarf.wikia.com/wiki/Talkie_Toaster) toaster, not a regular one. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [December 18, 2013, 5:33pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/7 "2013-12-18T17:33:39Z")
Note that turning a transistor on or off creates heat as well. This is the main reason chips get hotter as you run them faster. There are more on/off cycles per second and so more heat generated. The electrical resistance factor is more of secondary effect. Unneeded current needs to go somewhere once a switch occurs, so it ends up run thru higher resistive paths and out as heat. If a computer chip were somehow put into a given state and not switched, the resulting heat produced would be tiny. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 18, 2013, 5:34pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/8 "2013-12-18T17:34:56Z")
There are a great many moving parts. They’re just all really, really small. ---
**Author:** ![Habeed](https://avatars.discourse-cdn.com/v4/letter/h/a587f6/32.png) [@Habeed](https://boards.straightdope.com/u/Habeed)\ **Post date:** [December 18, 2013, 6:59pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/9 "2013-12-18T18:59:55Z")
A more accurate answer is to say that the heat is generated whenever a semiconductor connects itself to ground. Whenever memory is “zeroed” out this happened. This waste heat will always be generated whenever you destroy information. Making the transistors smaller means there is less charge wasted every time you do this, but even if you make transistors as small as physics will allow, there is still some. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [December 18, 2013, 7:19pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/10 "2013-12-18T19:19:06Z")
> [@DrCube](#): > > How exactly does your toaster generate heat? Just by [walkin’ down the street](http://hellogiggles.com/wp-content/uploads/2012/05/02/battlestar-galactica-tricia-helfer-as-cylon-number-six.jpeg), baby. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [December 18, 2013, 7:31pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/11 "2013-12-18T19:31:42Z")
> [@Habeed](#): > > A more accurate answer is to say that the heat is generated whenever a semiconductor connects itself to ground. > > Whenever memory is “zeroed” out this happened. This waste heat will always be generated whenever you destroy information. Making the transistors smaller means there is less charge wasted every time you do this, but even if you make transistors as small as physics will allow, there is still some. Mmmmm… CMOS transistors generate most of their heat when they are switching states, but these days a significant portion of the heat generated comes from leakage, and has nothing to do with switching at all. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [December 19, 2013, 12:52am UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/12 "2013-12-19T00:52:33Z")
> [@friedo](#): > > [Resistance](http://en.wikipedia.org/wiki/Electrical_resistance). There’s a lot of it. So why does switching to smaller processes improve efficiency? Resistance should go up. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [December 19, 2013, 1:17am UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/13 "2013-12-19T01:17:02Z")
Smaller transistors means it takes less charge to make a state a 1 instead of a 0. That means less current is required to change state. Going to lower voltages also reduces the charge needed for a 1, reducing the amount of current. On the other hand, faster clock speed means states change more often, increasing the current. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [December 19, 2013, 1:36am UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/14 "2013-12-19T01:36:09Z")
> [@friedo](#): > > [Resistance](http://en.wikipedia.org/wiki/Electrical_resistance). There’s a lot of it. Maybe if you tried reasoning with it. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [December 19, 2013, 2:17am UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/15 "2013-12-19T02:17:36Z")
I think it’s the lossy imaginary part of complex dielectric behavior in parts that are changing state. ---
**Author:** ![Flander](https://avatars.discourse-cdn.com/v4/letter/f/8c91f0/32.png) [@Flander](https://boards.straightdope.com/u/Flander)\ **Post date:** [December 19, 2013, 2:52am UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/16 "2013-12-19T02:52:39Z")
> [@Little\_Nemo](#): > > Maybe if you tried reasoning with it. [That never works.](http://hamgear.files.wordpress.com/2013/02/resistanceisfutile.gif) ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [December 19, 2013, 5:03am UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/17 "2013-12-19T05:03:08Z")
> [@Habeed](#): > > Whenever memory is “zeroed” out this happened. This waste heat will always be generated whenever you destroy information. ??? NO. Suppose I use ice cubes to represent 1, and melt them to be 0. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [December 19, 2013, 5:31am UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/18 "2013-12-19T05:31:09Z")
> [@Isilder](#): > > ??? NO. > > Suppose I use ice cubes to represent 1, and melt them to be 0. You’re sort of correct but only because you’re “cheating”. You’ve just arbitrarily chosen a low energy state to represent the 1 and the high energy stated to be the 0. For your ice cube system to be useable as a system for recording volatile memory, it’s going to have to change state from high to low and vice versa. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [December 19, 2013, 7:20am UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/19 "2013-12-19T07:20:37Z")
> [@beowulff](#): > > Mmmmm… > CMOS transistors generate most of their heat when they are switching states, but these days a significant portion of the heat generated comes from leakage, and has nothing to do with switching at all. Very significant. Back 20 years ago ASICs I worked on had quiescent currents in the microamp range. Now they are in the couple of amp range, and faster and bigger processors are even worse. And it gets worse as you increase voltages for speed. ---
**Author:** ![Jake](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@Jake](https://boards.straightdope.com/u/Jake)\ **Post date:** [December 19, 2013, 5:13pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652/20 "2013-12-19T17:13:55Z")
> [@Napier](#): > > I think it’s the lossy imaginary part of complex dielectric behavior in parts that are changing state. Well! That clears things up. 😕 Thanks all, for your responses. 🙂 [Next page](https://boards.straightdope.com/t/how-exactly-does-a-cpu-generate-heat/676652.md?page=2)