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Underclocking for a Quiet Machine? 62

Posted by Cliff
from the one-of-the-holy-grails-of-home-computing dept.
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?
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Underclocking for a Quiet Machine?

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  • by Anonymous Coward on Tuesday February 26, 2002 @05:25PM (#3073841)
    A C-64 plugged into my television. Silent, swift, and about the most supreme platform for Fort Apocalypse.

    Fuck that high falooting stuff. There's some halfassed word processor that'll work just fine for this beast. And I'm not joking about this shit.
  • I have always found fan noise annoying in the past while I was trying to listen to my N'Sync MP3's (Justin Timberlake is *so* cute!). It would always interfere with my thoughts and was generally a nuisence.

    Since I run an Athlon XP machine with lots of hot hard-ware in it, I found that underclocking to take a few degrees off of the CPU temperature was futile. It made about 10 degrees F of difference with the fan still on, and that just didn't seem like enough to risk my investment by running it without any active cooling.

    So, I went with a water cooling solution. Although I decided to roll my own system using components available over the Internet, there are several cases [hardocp.com] that come with water cooling built in. Some of them don't even require a water pump, which is a super big plus if need absolutely zero noise, like me. I've been quite satisfied with mine so far, however, your milage may vary.

  • The Silent PC (Score:4, Informative)

    by tfurrows (541222) <tfurrows@gmaiPASCALl.com minus language> on Tuesday February 26, 2002 @05:37PM (#3073959)
    Here's a real (non trollaxor) link to a site dedicated to silent computing....

    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.
  • You've likely noticed that as the processors get faster and hotter the heatsinks and fans got larger and more essential.

    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
    • You're not taking into account that more modern chips use smaller dies, and less voltage, thus producing less overall heat output for the same MHZ. However, smaller die means the heat that is there may be more concentrated.

      So in general, it may be possible to underclock the .13 micron die chips and have them run without a fan. It is simply a matter of how much to underclock, and whether the chip and motherboard support it (and whether your heatsink is adequate).
    • by itwerx (165526) <itwerx@gmail.com> on Tuesday February 26, 2002 @07:19PM (#3074807) Homepage
      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...

      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.

      • One thing to keep in mind, however; AMD chips allow you to alter clock settings based on both bus speed and the CPU multiplier where Intel only allows . Considering that the memory bus is one of the bigger bottlenecks in modern PCs, you'll see less of a performance hit by dropping the CPU multiplier and keeping the FSB high than you would by keeping a high CPU multiplier on a slow bus.
    • We've got a Dell Optiplex at work, P-III 500, that has no CPU mounted fan. It DOES have a big heatsink, and a plastic "funnel" mounted above it, leading to the chassis fan.
  • by zenyu (248067) on Tuesday February 26, 2002 @06:05PM (#3074253)
    I had an old workstation at home with dual PPro that I wanted to turn into a router. It had 5 fans, two on the CPU and three elsewhere. The case was a pretty big aluminium one so I took out all the fans and removed a CPU. It still wasn't cool enough by the place finger on heatsink test so I underclocked it from 200 to about 130, I couldn't get it any lower with my motherboard.

    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...
  • If you want to get a top machine, you are going to have to live with the noise. You can quiet it down a little if you pick the right components like i did - a good solid case, a special cpu fan and heat dissipator, a fanless graphic card, and hard disk noise insulators. But this is going to cost you $$$. Otherwise go for VIA C3 cpu based machines. These cpu's have low power consumption and low heat dissipation. But the old adage also applies here, you loose something with it. The graphics/sound/nic are generally integrated in the chipset, and they are fast, even if you look only at these cpu's clock rates.

    /Pedro
  • by whatnotever (116284) on Tuesday February 26, 2002 @07:08PM (#3074748)
    One day, I wanted to get a little more power out of my 90MHz Pentium system, but without any added noise (the p90 had a heatsink w/o fan). I figured I could throw a K6-2 in there and underclock it to the point where it would run fine with just a heatsink.

    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.
  • I'm not sure that having no cpu fan will make much of a difference for the total noise a system produces. On all of my boxes, the loudest component that always runs is the fan on the power supply. Hard drives and cdroms tend to be even louder, but they don't run full-time (unless you're a wee bit short on ram).

    Granted, I'm not running super-high end systems, but I doubt the cooling requirements of the newest AMD and Intel chips are such that they require a fan to run so fast that it's louder than the power supply, especially if you buy a decent quality one.

    If you have a way of monitoring temperature of your processor and motherboard, you *could* play around by reducing the voltages to the fans (both cpu + ps), to slow them down a bit. This might cut the noise to an acceptable level. Certainly not something I'd consider doing on a system that's important to you in any way, though!

    Of course, if you're a *real* geek, you have your big system sitting in a server room somewhere and connect to it with an xterm sitting on your desk!
  • I have a 333 k6-2 at 231 with just a heat sink in my mp3 playing machine. i left the power supply fan alone just to keep some kind of air flow in the box. It gets warm but not too warm ive never had problems with it.

    Im sure you could run your 1.8 ghz at 900mhz with no issues other than less performace because of the lowered clock speed but thats already expected. you may beable to get away with a 1Ghz or more depending on the quality of HS.

    if you need the speed or gonna over clock, water cooling is the way to go. but for your needs just find a nice HS.
  • easier way... (Score:5, Interesting)

    by Polo (30659) on Tuesday February 26, 2002 @08:50PM (#3075236) Homepage
    Here are the things you'll have to deal with when trying to quiet your system:
    • cpu fan
    • disk drive
    • case fan
    • video card fan
    • power supply fan
    • cd spinning
    Ok, so my way of solving the problem doesn't involve underclocking, but it works better:

    I put the computer in another room.

    Get a good monitor cable (one with ferrite cores) and a keyboard extension cable and run them through a wall to the computer in another room. Now *that* is quiet. And it costs maybe $50.

    Now to be honest, that's not exactly my setup. I actually have a KVM switch and hook to several computers in the next room. I have a nice quiet bedroom with a keyboard, monitor, speakers and a usb KVM switch. If you look at http://www.belkin.com you'll find kvm switches that switch audio too.
  • My theory (Score:3, Interesting)

    by pete-classic (75983) <hutnick@gmail.com> on Tuesday February 26, 2002 @10:11PM (#3075582) Homepage Journal
    It seems you could save even more heat by underclocking a fair bit, then undervolt it a bit.

    I haven't actually tried it, and I'm sure some joker who doesn't know what he is talking about will chime in here and pose as an engeneer and say it can't be done, but I really thing this will work.

    You won't be able to lower the voltage much, because you'll need to meet a certain minimal signal level. OTOH, less clock means less noise, and every little bit helps.

    Also consider using a notebook HDD. Quieter and cooler.

    Good luck!

    -Peter
  • Underclocking (Score:4, Informative)

    by zsazsa (141679) on Tuesday February 26, 2002 @11:21PM (#3075805) Homepage
    Several people on the Silent-PC mailing list [yahoo.com] have underclocked and under-volted their systems, but I don't think anyone has been able to run a modern CPU such as an Athlon or P4 without a fan. Some people have reported success with older Celerons and K6-2s, however.

    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
  • by geoswan (316494)
    Interesting idea. This site has numbers for the power consumption of a range of processors. Note: The more modern processors consume way more power than older ones, like a P233mmx.
    A two gigahertz P4 can comsume 100watts. As much as a light bulb. Ouch!

    P4 power consumption [sandpile.org]

  • ok this is pretty easy... get a chip that doesnt put out alot of heat like a low end Athlon XP or a Duron. Throw in some WC gear from Danger Den [dangerden.com], a 120mm 60cfm fan (they're almost silent), and you're set. If you worry about the chipset and GPU, put waterblocks on those too. Also remove any other case fans you have, the 120mm fan as a blowhole will work nicely unless you have a really hot system.

    As for the HDD, I'd suggest a Seagate Barracuda ATA IV, they are almost completely silent.

    Now get a PSU with a speed-controllable fan (enermax has a few) or a temperature controlled fan (Antec SmartPower) and you're set, almost complete silence.
  • Redundant (Score:5, Informative)

    by Perdo (151843) on Wednesday February 27, 2002 @12:09AM (#3076004) Homepage Journal
    I have an 1800xp underclocked from 11.5*133 @ 1533mhz to 7.5*133 @ 1000mhz. With an MC462 heatsink and a tube fixed to the heatsink an exiting the top of the case and no fan, the CPU never exceeds 32 degrees celsius. The real test is to see how far you can drop the CPU voltage before instability arises. Mine is running at 1.65. Lower voltage plus lower frequency means less heat but remember I am using one of the highest rated heatsinks available. At 789 grams, this heatsink weighs almost 300 grams more than any other heatsink you can buy.

    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)

    by (startx) (37027)
    What's working for me right now is a 1.4Ghz t-bird, underclocked to 1Ghz, with a slightly lowered voltage. On top of that is a 100% Copper OCZ Goliath (I think that's the name) heatsink with the 60cm delta fan removed.

    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.
  • Are you sure that 1.8ghz running at 900 mhz would be any faster than your PIII 600? To reach higher and higher clock speed chip makers have to make trade-offs, deeper pipelines etc, so, mhz for mhz, older processers are often faster.
  • by satch89450 (186046) on Wednesday February 27, 2002 @03:25AM (#3076418) Homepage

    I've seen a huge amount of discussion over the past few years about doing things to computer cases to deaden sound. Now, one person in this discussion started thinking outside the box, talking about his putting the computer into the next room and running cables through the wall -- effective to some extent, but absolute hell when you have to put a CD-ROM into the drive, don'tcha think...

    What I've been looking to do is build a proper sound-controlled cabinet for my computers. It would be an enclosed cabinet with doors, fans (ducted at inflow and outflow ports with sound-proofing material) to ensure enough air flow to keep internal temps down, built-in power distribution, built-in Ethernet (I have a 24-port 100-base T hub), and sound-sealed cable ports for the KVM switch and external connections.

    Some design points:

    1. The cabinet needs to be deep enough so that the system units will have adequate front and rear clearance for airflow. Experiments with standard cases tells me that you need at least four inches rear clearance and six inches front clearance. The extra clearance in the front is dictated by CD-ROM and DVD-ROM drives, so that the door of your cabinet doesn't interfere with the CD/DVD-ROM tray. Given that the deepest cases are about 20 inches, that means you need an inside depth of 20 + 4 + 6 = 30 inches. Plan on 36 inches of depth for the outside dimension

    2. Your primary sound barrier will be dense material, such as plywood. If you can get birch plywood, this will give you better sound control because of the increased density of the wood. It's tempting to go very thick, but 5/8 inch should be plenty good. Consider using 1x6 for the framing, and be sure the plywood is braced at least every 18 inches with framing.

    3. Most acoustic treatments will require about two inches of depth in order to be effective across the "band of annoyance" (200 Hz to 4 kHz). Thick-pile carpeting (make sure it's flame-retardant!) can be surprisingly effective, and cheap when purchased as end-rolls or remenants. Fiberglass batting and rock wool are also effective, although the stuff is tricky to work with safely. For the sides and the rear wall, standard acoustic tile or ceiling panels can be effective. For ducts, the goal is traverse absorption, so materials like acoustic tile may not be appropriate as they tend to best absorb sound hitting the tiles perpendicular to the surface.

    4. Design the airflow so that air deflects around sound baffles; this prevents direct ray-path propagation of unwanted noise. For example, an air intake can be done by using a front floor-level opening, a baffle panel of burlap-covered 1/4-inch plywood, and a 5/8-inch plywood shelf for the computers that stops six inches from the front of your cabinet. This design directs the airflow to the front of the computers, which from most cases seems to be the most desirable. A similar baffle system at the top of the cabinet can serve to exhaust air, again using baffle panels to break up any direct ray paths.

    5. Any air-motion equipment should be suitably baffled as well. Large low-RPM fans work better than small high-RPM fans.

    6. Finally, cable ports need to be sealed acoustically. Consider rubber gasket material, or the "tube foam" you can find at some fabric shops.

    For my prototype, I'm using a rack cabinet I got at an auction last year. The metal skins (including the top one) is replaced by 5/8-inch plywood, faced on the inside with long-nap carpeting. The air intake at the bottom of the cabinet uses exactly the baffling technique I described above, using burlap soaked in fire retardant. Air exhaust is still a problem. Cables go through two slots in the back of the cabinet. The "door" is currently a removable panel of carpet-faced plywood, but I have designed a quad-door arrangement - this lets me get access to the CD-ROM drives without opening the entire front, yet provides for service access easily.

    Temperature monitoring is a bit of a problem right now, a problem I hope to solved via eBay.

    When I have more, I'll put it on my Web site and let you all know about it.

    (One thing: I'm a bachelor, so I don't have a wife to worry about. Your mileage may indeed vary.)

  • AMD recent years have been known to produce inexpensive and good performing, but hot running CPUs. They used to rely on external measurement of temperature, but in 2001 they, like Intel a long time ago, introduced internal temperature sensoring. AMD still can not be said to produce cool running processors, which also seems to be the fact for many of the most recent Intel ones, but since they aren't so expensive some say a solution for a quiet PC can be to buy a fast AMD processor and underclock it, making it run cooler thus minimizing noise of active cooling.

    From http://home.swipnet.se/tr/solutions.html

  • i'm pretty certain that one dont have a fan. why not look at one and pick up a few ideas wrt ventilation and heat sink configurations. also, i believe that the p3 celeron should suit your needs. for one, it's .13 micron and hence cooler, and it won't come with the heating issues that plaguee the p4 like slowing down all the time ... oh wait a moment ... that's your plan ...
    • I agree. But one big lesson you can learn from the Cube is to "cheat" on the power supply. ie, make it a massive external brick that gives off a fair bit of heat, has no fan, and sits under your desk.

      That's half the magic behind the Cube's size and silence.

      I'd love to see a third party create fanless power supplies that are plug-and-play replacements for the PC world.
  • Personal Experience (Score:3, Interesting)

    by Lomby (147071) <andrea @ l o m b a r d o n i.ch> on Wednesday February 27, 2002 @07:59AM (#3076872) Homepage
    Once, I set up a Linux file server for a very heterogenous network (AppleTalk,FTP,NFS,Samba).
    Since performance was not an issue (about 10 clients).
    I decided to underclock the processor (a very old CyrixPR166). The right clock speed would have been 133, but I clocked it to 100.
    This was a zero maintenance server, in fact it ran for about two years without a single problem.
    After two years, it needed an HD upgrade, and I opened it, to insert a new HD. To my surprise, the CPU fan broken, and in fact, from the dust I guess it didn't work for some months, but still the CPU had no temperature problems.
    What's the moral of this story? Don't use the muscles (Mhz) if you don't need to! :)
  • Remember those tom's hardware videos of amd chips burning in flames and pentium 4 working fine when the heatsinks were suddenly taken off?

    Don't worry about any underclocking. Just run the chip as is with as much cooling as you feel like it and it will automatically adjust it's speed to suit the conditions.

    Note. I will take zero responsibility for any direct or indirect damage to your system that results from the advice above. It should work but you can't tell for sure until you try..
  • I am on a mailing list where people discuss using a PC with a DSP card to do real time audio processing (often with linux I should add). Why - after expending enourmous effort to ensure that all your transducers are perfectly time aligned, crossed over optimally and your room reflections are cancelled - would you put up with fan noise? The answer is these guys don't. Here is what one list member said of his recent test running a 0.13 Celeron:

    "First off, I'd like to say that Celeron .13s are officially great. :)

    I bought a 1GHz .13 last week, and successfully undervolted it to 1.3V. Initial tests at 667MHz with only a passive heatsink and sideways PSU ventilation were very successful (~36C top temp)... ran it for 3 hours solid using 3DMark2001SE with no problems.

    So then I tried it at the rated 1GHz, not expecting it to even boot. But absolutely no problems here either. Top temp nudged up to ~38C, and of course performance was vastly improved. Just in case you think the thermistor is lying, I did the "finger test", which suggested <40C."

    The 0.13 celeron is the one made with the PIII process and is sometimes called the Celeron II. It's a good chip. I personally have one these 800Mhz chips overclocked to 1066Mhz, using the stock Intel fan and heatsink. It barely gets warm.
  • Does such a thing even exist for desktop machines? The noisiest part of my workstation is the power supply fan. If someone could manfacture an external one, it would be practically silent. I think.

    It would be great to be able to connect a small power connector like a laptop. How practical would this be?

    I am no electrical engineer, but I don't see why this isn't feasible. Seeing as it would be outside the case, it could be covered in heat sinks, cooling fins, not needing a cooling fan at all. Might get a little hot, but at least it'd be silent.

    Come on. Someone here has to be able to build one.
  • From personal experience having a very small amount of airflow is a huge cooling improvement over no airflow at all. (Think of how cool a slight breeze can be on a hot day.) A 12V fan running at 5V (1500-2000rpm) is virtually silent. my favourite mods. Open the power supply and solder its fan onto 5V rather than 12V. A good power supply will have good heatsinks so you can get away with this. Cut two straight bits of a paper clip stick them into gnd and 5v on a spare floppy plug then stick your processor fan on the other end. Some fans work at 5V some dont. I have my intel fan running at 7V if you still want the motherboard to monitor the fan speed you need to connect the pulse line from the fan to the motherboard. (yellow or green one) Im running a 900mhz Celeron and a 1Ghz Athalon like this and they run fine at about 40 C while both encoding DVD to divx. On a hot day too (35 C) I also ran a PII350 for 2 years without a fan. it ran at 60 to 70 C mostly. at 75 the mboard beeped at me (hot days) and usually meant i was playing too many games. Began running it at 400mhz with the original fan slowed down to ~1500rpm 7V and it ran stable at 30C
  • The power supply is likely to become the largest noise source. I would recommend buying an Enermax (whisper) or equivalent since they really are silent.

A language that doesn't have everything is actually easier to program in than some that do. -- Dennis M. Ritchie

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