Underclocking for a Quiet Machine? 62
The Fun Guy writes "I'm running a PIII 600MHz, which I'm thinking of upgrading. If I could get rid of the fan and run more quietly, I'd love to. I run office-type apps, so I don't need the fastest processor around, but I also run d.net, so I'm constantly pegged at 100% usage. Aside from the obvious fact that your CPU is running slower than the listed speed, is there any downside to buying, say, a 1.8GHz chip and running it at 900MHz without the fan? Any experience or FAQ's to share on this?" We've covered this topic several
times
before, with some good feedback, however most of the approaches don't discuss the use of underclocking to accomplish this, although one common suggestion from the comments is to use a non-Intel processor, if you can. Have any of you tried underclocking your CPU to allow it to run silently? How far do you need to underclock a processor in order to enable it to run without a fan?
The Silent PC (Score:4, Informative)
http://home.swipnet.se/tr/silence.html [swipnet.se]
I say take a break from the computer room, or use a laptop, or maybe turn the computer OFF every once in a while if you don't like the noise, but hey, to each his/her own.
Underclocking won't help very much... (Score:1, Informative)
The basic equation you'll run into is that for a given amount of processing power the cpu is going to be releasing a given amount of heat. If that heat is not dissipated it'll build up destructively.
The last processor I saw without a fan was a PII 300, and that had a heatsink twice as large as a normal fan heatsink situated directly below the power supply - which meant that it got a good deal of active cooling.
In order to effectively cool a modern processer (which does put out less heat per clock cycle than older processors, but not by much) you cannot just slap a large heatsink on it, slow it down, and expect it to have enough cooling.
In short, the only downside other than having a slower computer is that it won't work. A 1.8GHz processor running at 900MHz is going to let off as much heat as a processor in the same family rated at 900MHz, which surely needs cooling.
The 1.8GHz processor is letting off more heat than the 900MHz. The reason you can use the same heatsink and fan is that the heatsink and fan are overrated for the 900MHz, but not so much that the fan is not required.
Lastly, current processors are pipelined dynamic machines, meaning that they have a range of clock speeds in which their output will be valid. Too slow and they stop working, too fast and they stop working. You're generally safe underclocking a processor whose same die includes processors at the lower speed, but be careful, since higher speed variants generally have some small die changes which are not great enough to tell anyone, but do affect the range.
This field (thermal dynamics) is rife with documentation and resources. You should be able to calculate the heat output of the processor and determine the correct sizing heatsink. Don't be surprised if you find it requires a passive heatsink size of greater than 81 square inches, with a surface area significantly larger...
-Adam
Re:Underclocking won't help very much... (Score:3, Informative)
So in general, it may be possible to underclock the
done it with some old CPU's (Score:3, Informative)
At this point it ran cool, but it wasn't quiet at all. The hard drive was the newest component and it was friggin loud. I took that out and made an LRP type floppy and now I sleep next to the thing.
This used to be a workstation that I woke me up from across the room even when I placed it behind a bookcase. But the real moral here is that you need to get rid of that hard drive, even if it goes to sleep quickly the thing can wake you up when it starts spinning to record some log or whatnot. I also got rid of of extra stuff like the power supply cover and tapedrive and what not that just weren't good for airflow. In terms of time spent the router would have been cheaper, but it was fun and the thing is flexible.
I think that If I ever build a fast machine that needs to be on all the time I'll just find a way to hang it outside my double pane windows. Long cables...
There is no such thing as a free lunch. (Score:1, Informative)
/Pedro
My experience (older hardware) (Score:3, Informative)
I got a 300MHz K6-2. It went in fine, and I started it out around 200MHz. But my network card (3COM 3C905-tx) freaked out. It dropped packets like crazy and wouldn't even hold a link to my switch for more than a second at a time. Uncerclocking even more made the situation a little better, but I could never get the network card completely stable.
Eventually, though, I *was* running the K6-2 without any heatsink whatsoever, and it only got warm to the touch. This was around 100MHz.
That was even running it at 2.5V, when it only required 2.2V even at 300MHz. Since it was underclocked, it would have probably run below 2.2V, which would have been far cooler than what I had.
Unfortunately, my experiment came to a rather spectacular end when I decided to put the heatsink back on while the system was on. The heatsink clip paid a visit to some pins of a power transistor nearby on the motherboard. Let's just say that sensitive digital equipment like a motherboard isn't supposed to make sparks. Surprisingly, the motherboard was fine - but the cpu was toast. I just went back to using the P90, a little miffed about losing $15, but otherwise fine.
Informative?? Not...! (Score:5, Informative)
Umm, yeah, right, you don't know much about CPU design these days do you?
Discounting the above, my own real world experience has been that Intel CPU's can typically eliminate the fan with a 20-30% underclock. AMD is almost not worth it needing at least 50% underclock. Also you NEED the biggest darn heatsink you can find and I strongly recommend active heat monitoring and some sort of automatic powersaving idle/shutdown/whatever if you leave the machine alone for long periods. Somebody mentioned large heat-sinks being close to the power-supply fan intake, this is a good idea and can be accomplished by using a duct (and possibly some judicious cutting) if your power supply vents are inconveniently situated.
Underclocking (Score:4, Informative)
You could also buy a CPU that can run at 933MHz without a fan [siliconacoustics.com], the VIA C3. It's pretty good, but the FPU is quite anemic. Personally, I think it's a small price to pay for some peace and quiet.
Ian
Redundant (Score:5, Informative)
And yes, the chimney effect of the tube makes it feel like there is a fan blowing hot air, just like the G4 cube.
Good coper heatsink (Score:2, Informative)
On a side note, that delta is one of the loudest SOB's out there, but it kept it mighty cool back when I had my machine foolishly OVERclocked, and didn't realize that for what I was doing 1Ghz was plenty fast.