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AMD Hardware Hacking Hardware

AMD Athlon64 4000+ Underclocking 286

Posted by CowboyNeal from the slowing-things-down dept.
Bios_Hakr writes "PC Stats is running an article on their experiences underclocking an AMD 4000+ processor. Their goal was to try and reduce the voltage requirements and lower the heat output. They benchmark using 3dMark01, 3dMark05, as well as SuperPi. From the article: 'This got us thinking though; what about under-clocking? Most modern processors and motherboards can just as easily run under a rated speed as it can run over... but is there a point to this? Well possibly.'"
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AMD Athlon64 4000+ Underclocking More

AMD Athlon64 4000+ Underclocking

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  • The point is.....?

    If you want low power you can buy systems specifically designed to perform well on low power supply.

    • The point is...

      Suspense = more clickthroughs = more ad views = more revenue.

    • Re:Don't keep us in suspense (Score:4, Informative)

      by B'Trey ( 111263 ) on Saturday June 04, 2005 @09:41AM (#12723264)
      RTFA. From the article:

      Case fans can generate some audible noise in an environment designed for quiet, and is this really acceptable? Professional studios can acoustically isolate computers, making this a moot point, but home audio enthusiasts don't have this luxury. The question is, how much heat and voltage can be dumped by underclocking a given processor (down) while still retaining acceptable processing performance?

      The purpose of this article is to take a very fast, very hot modern processor (in this case an AMD Athlon 64 4000+) and underclock it with an eye to comparing performance to levels of heat and voltage at below stock speeds. The Athlon 64 is currently the fastest available desktop processor, so we reasoned that reducing its speed to the point where it could be operated silently with a passive cooling system should still leave us with a powerful machine for everyday tasks.
      • I read the article and basically decided that the authors were a bunch of overpaid muppets with too much time on their hands.

        e.g.
        http://www.transmeta.com/success/desktop.html [transmeta.com]
        http://www.transmeta.com/success/workstations.html [transmeta.com]
        http://www.transmeta.com/success/sbc.html [transmeta.com]
        http://www.transmeta.com/success/server.html [transmeta.com]

        etc etc etc.

      • Re:Don't keep us in suspense (Score:5, Insightful)

        by pla ( 258480 ) on Saturday June 04, 2005 @09:55AM (#12723350) Journal
        a very fast, very hot modern processor (in this case an AMD Athlon 64 4000+)

        Very hot? If you haven't already bought one, just make sure to get one with a Winchester or Venus core.

        Using C&Q, mine (only a 3000, but "close enough" to make my point) could probably get away with purely passive cooling. Using a meter at the plug, it draws a whopping 54 watts average, with 48W idle (C&Q engaged) and 65W max.

        Thanks to modern CPU power saving technologies as implemented in all newer Athlons and Opterons, or Pentium M, you really don't need to sacrifice peak performance for the sake of power and heat. They deal with usually sitting there idle fairly well, by throttling back, without needing to resort to such (relatively) drastic measures as "suspend" and "hibernate".


        I do, however, see one possible use for underclocking... When you keep your CPU always pegged at 100% (running Seti @home or the like, for example). Then, underclocking would allow you to trade a little bit of performance for a lot of power and heat reduction.

        • Re:Don't keep us in suspense (Score:5, Interesting)

          by pla ( 258480 ) on Saturday June 04, 2005 @10:06AM (#12723403) Journal
          it draws a whopping 54 watts average

          Oops... Just to clarify, the entire system, including power supply losses, draws that much. The CPU itself, from what I've read (published numbers seem to vary a LOT, and I'd love to see some hard data on the min, mean, and max draw of the 90nm Athlon 64s), only eats between 7 and 35W (for comparison, the Pentium III line came in at the low 30s) with a theoretical max somewhere in the 60W range.


          Kinda funny, actually... When everyone talks about needing bigger and better power supplies, with 400W considered a bare minimum and 600W not all that uncommon these days, I upgraded from an old P-III system and the total power consumption of the system dropped by half.
          • I think the power supply requirements are more based on a gamer rig than your everyday Joe workstation. Incredible video cards, multiple hard drives (possibly in RAID configuration striped for speed,) overclocking, cooling systems, and then bling (flourescent lights, etc) all suck down power. I doubt that a power supply will always draw it's peak power, so having a litttle headway is worth it to keep the system a little stable.

        • Idle? (Score:3, Insightful)

          by CustomDesigned ( 250089 )
          My system is never idle. It runs seti@home and/or folding@home 24/7 in the background. So I don't think the power saving features will work for me if they depend on the processor being idle. I bought a Dell 500SC for home. It has been rock solid, but the fan is very noisy, and the DMA on the secondary IDE is busted (chipset bug). When I upgrade, I don't care about bleeding edge performance, I want it to be quiet. Wouldn't you know, after I bought the 500SC, Dell came out with the 400SC, which I've ins
        • If you haven't already bought (an AMD Athlon 64 4000+), just make sure to get one with a Winchester or Venus core.

          Nitpick: the 90nm 4000+ is a San Diego core. 1MB L2 cache is San Diego, 512MB L2 90nm E3 core is Venice, D-series core is Winchester (older 3000+ to 3500+). (You have to be this geeky to get a 4-digit /. ID. It's a law.)

          I did the same thing you did. I've got a Winchester core 3000+ in my 64-bit Fedora Core server. You can cut power consumption even more with a high efficiency power suppl

          • Nitpick: the 90nm 4000+ is a San Diego core. 1MB L2 cache is San Diego, 512MB L2 90nm E3 core is Venice, D-series core is Winchester (older 3000+ to 3500+). (You have to be this geeky to get a 4-digit /. ID. It's a law.)

            Um, does the Venice core really have half a gig of L2 cache ?-)

        • You mean "Venice" core.

    • If you want low power you can buy systems specifically designed to perform well on low power supply.

      The article is about researching how to build such systems out of cheap commodity parts, unlike the proprietary, often Windows-only parts found in laptop computers.

      • Hmm, a athlon64 4000 is not exactly cheap, and the recent "notbook" boards like the aopen i855 work perfectly under linux, even with speedstep. (my 1,7 Ghz doltan currently running perfectly smooth at 600 Mhz, and will get faster if i utilize the cpu)

        So .. what's the point in underclocking an expensive CPU ? Rather than buying a CPU which is specificly designed for the task ?
        • So .. what's the point in underclocking an expensive CPU ? Rather than buying a CPU which is specificly designed for the task ?

          Not much, especially when they could have used a $150 Athlon64 3000 for this test. That was the silliest part of the whole thing... Using a high-end power-sucking 3D card (with an active cooler no less) was the second silliest.

      • Via and Transmeta do commodity boards and CPUs for low power systems. No fans, minimal cooling needed and yet still with decent performance. This article is *just* *plain* *dumb*.

      • The article is about researching how to build such systems out of cheap commodity parts, unlike the proprietary, often Windows-only parts found in laptop computers.

        (The UK) Personal Computer World have an article in the current edition about using the 'Pentium M' processor in desktop machines. Mobos *are* available that support these (Abit IIRC); as well as adaptors that allow certain ordinary P4 motherboards to accept a Pentium M.

        For my money, these look like a good compromise between the micro/nano-A
      • While the principle has some merit, the authors of the article picked the worst possible example. AFAIK the Athlon 4000+ is still manufactured in 130 nm technology ("Clawhammer"), and it is not exactly cheap. For less money, you can get an Athlon 3800+ with the new Venice core (90nm technology) which uses MUCH less power than the 4000+.
        Unfortunately, the article does not give any numbers on the actual power consumption or ambient temperature, so we have to look elswhere:
        LostCircuits http://www.lostcircuits. [lostcircuits.com]
    • I have an Athlon 2100+ which I bought back in 2002 when it was brand new. After installing it, I experienced frequent lockups as the CPU overheated under heavy loads. I bought a new heatsink/fan combo (a Thermaltake Volcano 9, which was pretty good at the time) to replace the standard AMD one, but it sounded like a jet turbine at full speed and it only alleviated the problem a little. After that, I underclocked my FSB by only 3MHz (133MHz to 130MHz) and I haven't had a lockup in over a year. The associated drop in performance is unnoticable.
      • Let me guess... you've got your 2100+ installed
        on an AsRock motherboard, yes? I've got two
        2600+ systems with identical heatsink/fans.
        The one in a MSI KM2M motherboard is rock-solid
        stable at full FSB speed (133MHz), but the one
        in the AsRock K7VT2 has to be underclocked to
        130MHz FSB or else it constantly locks up.


        I'm guessing your problem was never cooling,
        it was getting stuck with a cheap mobo, as I did.

    • I don't get it. If you wanted a low power system, why would you buy the top chip and underclock it?

      The Athlon64 4000+ is a Hammer chip, iirc. It's manufactured on a 0.13nm process, and is a slightly older core. Instead of using that chip, why not use the Athlon 3800+? The Winchester and Venice cores are both 0.09nm chips, and run much, much cooler and dissipate much less heat than the Hammer cores. And you can use AMD's Cool n Quiet (aka PowerNow) technology to back off the processor speed to half speed
      • A key point here is that you can scale both the clock and the voltage. The power dissipated each time you get rid of a stored charge is proportional to the voltage squared. How often you do this per second depends on the frequency. Thus if you can run at half the voltage and one third of the frequency, then the processor dissipates 1/12 of the power!

        A fair comparison of processors would be to calculate how much processing power you get in some benchmark per Watt of power dissipated: Fan noise for getti

    • It will definitely make your system more stable. Unless you do something stupid with a refrigeration unit and/or very expensive water cooling, overclocking will make no percievable difference apart from a small increase in a synthetic benchmark.

      If, however you underclock your FSB by just a small amount, it will make both your CPU and your memory more stable and dissipate less heat, and you won't notice any percievable performance difference. It will also mean that those components are substantially less li
    • The systems on themarket designed for low power (trmansmeta, et al) are desiged for minimal power, at the great expense of cpu horsepower. The article is more about building a system with the greatest possible horsepower without needing noisy or failure prone cooling methods. Perhaps you want a fast computer that's going to go into your bedroom or home theater, where noise is an issue (my TIVO keeps me awake at night sometimes, so I can sympathize).

      Many /.ers have entioned that you should just buy a lo
    • Can't they just depress the 'turbo' button?

  • next article (Score:5, Funny)

    by Arctic Dragon ( 647151 ) on Saturday June 04, 2005 @09:32AM (#12723215)
    Their next article: how to remove 2 cylinders from your Ferrari's V12 engine.

    • Re:next article (Score:4, Informative)

      by TERdON ( 862570 ) on Saturday June 04, 2005 @09:51AM (#12723324) Homepage
      Actually, the parent poster is more insightful than the mods have thought (modded +4 Funny right now). There actually are engine control systems for motors with more than 4 cylinders that automatically turn off a few cylinders when running at low load. That moves the working point for the remaining cylinders to a more economical point (ie running at very low load is very inefficient), saving fuel (but not as much as when choosing a smaller motor - but maybe you just need the power sometimes etc).

    • Re: (Score:3, Interesting)

      by account_deleted ( 4530225 )
      Comment removed based on user account deletion
      • I sure hope they do a better job than Cadillac had when they did that in the early 80's. Wasn't the most popular of features and didn't really help with fuel economy.

        =Smidge=

  • Easier solution: Just run windows (Score:5, Funny)

    by carcosa30 ( 235579 ) on Saturday June 04, 2005 @09:32AM (#12723219)
    Most modern processors and motherboards can just as easily run under a rated speed as it can run over...


    Microsoft operating systems and software accomplish this without all the work.
  • Unfortunately... performance and heat seem to move proportunately. I would love to see (or hear) a silent server room. Hmm... maybe with embedded systems getting more powerful this will one day be a reality.
    • Look it up on Google, you could have a near silent server room today. AMD and Intel suck, literally (power & AC).

  • Underclocking makes sense to me (Score:5, Insightful)

    by Dolphinzilla ( 199489 ) on Saturday June 04, 2005 @09:36AM (#12723239) Journal
    If you are designing a system for high reliability, under temperature extremes and such (military environments for example) underclocking is the way to go - you can minimize power and heat loads as well as potentially avoid timing instabilites that occur when you push a processor to the performance margins.

    • Re:Underclocking makes sense to me (Score:5, Insightful)

      by ignorant_coward ( 883188 ) on Saturday June 04, 2005 @12:09PM (#12724117)

      For high reliability, I'd just buy a pre-engineered system from IBM or Sun rather than put on my engineering hat and pretend I know what I am doing.

      For hobbyists, all this is good and fun, but I'd hate for my anectdotal experience of one machine running underclocked well to be the underpinnings of a business webserver.

  • Er, did they hear about Cool'n'Quiet? (Score:3, Insightful)

    by marat ( 180984 ) on Saturday June 04, 2005 @09:38AM (#12723243) Homepage
    I thought what they are testing is the whole point of AMD Cool'n'Quiet technology, but they don't even mention it in the article! Nice try reinventing the bicycle. I'm already underclocking my Athlon 64 right now, thank you.
  • ... if there are annoying fans on the motherboard as well as on the GPU?

    You would think the whole point gets moot - the system certainly won't be quiet. (I believe there is an actual need for quiet systems eg in recording studios etc - which make the article interesting, but not great).

    • You'd hardly ever need to downclock a client/gaming machine. You do this with a server. A server doesn't need a fast GPU, so no need for a fan on it. Downclocked CPU means whole system downclocked, so you can apply passive cooling to the motherboard. There's still a problem with the PSU, but use one with some 200 spare watts, and spin its fan down using, say, a resistor in series, so it works quietly.
      If you want a quiet desktop, use water cooling. For everything.
      • Yes, I also realize this. Should have put an [/irony] at the end, perhaps. :)

        My point was that in TFA (oops - we're on Slashdot, no one have read it) they use use some high-end Radeon and a motherboard with one of those annoying northbridge fans, mooting the point of a quiet CPU cooling setup alltogether. Not really the setup you (and I) are suggesting...

      • A server doesn't need a fast GPU, so no need for a fan on it.

        Ehm, why would a server need a GPU at all?

        Are you telling me you would spec your server with a GPU (albeit a slow one)? Eek! Round my way servers dont have any GPU at all, not even a graphics card. Console is on a serial line to a terminal server...
    • Not every motherboard has a northbridge fan. Thank goodness.
  • Most modern processors and motherboards can just as easily run under a rated speed as it can run over... but is there a point to this? Well possibly.



    My gut instinct tells me.... Maybe!

  • Not useful information? (Score:4, Insightful)

    by erroneus ( 253617 ) on Saturday June 04, 2005 @09:43AM (#12723281) Homepage
    I think it is somewhat useful information. While most people are thinking about how much faster you can process, many of us are looking to reduce the noise of fans blowing. I recall when 800MHz was a fantastic speed... hell, for that matter, 300MHz was pretty nice too depending on how far back you go.

    And are we really using all of those cycles? Not really. Right now, a system's performance (IMHO) is largely the responsibility of the quality of RAM, Video and system board stuff. After all, what "feels" fast must be fast. If I've got a slow hard drive, then it's a slow system and if I can accellerate the video, then it's a slow system. What good is 4GHz if you've got a slow everything else... and by the same token, if you've got a fast everything else, a 2GHz processor is probably plenty.
  • I decided to underclock some 1U systems (~XP 2500) to ensure that they would never overheat (longevity was more important than performance).

    It works perfectly: a drop of 20% in core clockspeed greatly reduced the heat output, the core temperature dropped by almost 10 degrees C.
    • Cos by buying a 1U system with a slower CPU in the first place you could have saved money as well as reducing the temperature and power requirements.

      • Not necessarily. The higher-rated processors are often made with a smaller process. This is the reason they can operate at the higher clock speed without overheating in the first place. This A64 4000+ is probably (?) the first in a new line made with a smaller process.
        • "This A64 4000+ is probably (?) the first in a new line made with a smaller process."

          Um, no. The 4000+ they're using was released last year. The latest A64 processors on the market are rev. E (also known as Venice), which are in 3000+, 3200+, 3500+, and 3800+ flavours. There *is* a new 4000+ out, based on a new core (San Diego), but it's pretty clear that this review is using the old one.

          • Ah right, thanks for the info. I didn't know about the various parts, but my point still stands. The cores made with a smaller process produce less heat and (I'm pretty sure) require lower voltage. So running a 4000+ part at the same speed as a 2000+ will make it cooler than a 2000+ part running at its intended speed. That's what this article is about.

  • Their Maths is a little suspect in places (Score:5, Insightful)

    by kabbor ( 856635 ) on Saturday June 04, 2005 @09:45AM (#12723292) Homepage
    They listed the drop in temperature from 33.5 to 26.9 as a 20% drop. However, they didn't mention the ambient temperature. If you take 20 degrees, then this drop is more like 50%. That would also mean that it was consuming well under half the power. (I'm assuming watts->degrees is exponential.)

    As a secondary matter, the person who got me interested in BSD, as a rule, made his servers with whatever was the cheapest AMD-K6, underclocked to 350MHZ. Bulletproof boxes with long lifetimes. I'm sure there are still some churning out the bits around this town.
    • I'd guess that the ambient air temperature was in fact 23.6 C. This would give the expected 66% drop in heat production which would be consistent with the rest of the benchmarking results. Granted we wouldn't expect a perfectly linear relationship between heat production and clock speed, we would expect there to be a nearly linear relationship between heat production and performance for the same CPU. It's sad commentary that the persons writing these articles don't have a basic competency in physics or e

    • The real results (temp increase vs absolute temp) (Score:5, Informative)

      by ziegast ( 168305 ) on Saturday June 04, 2005 @11:38AM (#12723940) Homepage
      I agree 100%. I went through a bit of work to explain this to PCstats before I noticed that others on slashdot noticed the same thing I did. The information below may be redundant, but shows more detail.

      --

      The article states:

      "While there was a noticeable drop in temperature, it was not a huge one. From 2.4GHz to 800MHz, the temperature decreased by only 6.5 degrees Celsius. To put it another way, for a 66% drop in speed there was a 20% drop in temperature. This makes a bit more sense if you look at the numbers in terms of Voltage not speed; a 43% drop in voltage producing a 20% drop in heat seems more reasonable. The largest temperature drop occurred between 1.3V and 1.25V, where almost 1.6C of heat was shed."


      Unless the computer and participants were in a frozen room (at 0 degrees celcius), their analogy is flawed. The amount of heat generated is directly preportional to the temperature INCREASE above the ambient temperature. Let's assume that the test occurred at "room temperature" (70F deg or 21C deg). The chart would look more like the one below:
      Speed/Voltage____Temp__+Temp___MHz%_____V%_Temp+%
      2.4 GHz/1.40V 33.5C +12.5C 100.0% 100.0% 100.0%
      2.2 GHz/1.35V 33.0C +12.0C 091.6% 096.4% 096.0%
      2.0 GHz/1.25V 30.4C + 9.5C 083.3% 089.2% 076.0% -- Best return on drop
      1.8 GHz/1.10V 29.5C + 8.5C 075.0% 078.6% 068.0%
      1.6 GHz/1.00V 28.8C + 7.8C 066.7% 071.4% 062.4% -- "Knee" of curve
      1.4 GHz/1.00V 28.3C + 7.3C 058.3% 071.4% 058.4%
      1.2 GHz/0.95V 27.9C + 6.9C 050.0% 067.9% 055.2%
      1.0 GHz/0.85V 27.6C + 6.6C 041.7% 060.7% 052.8%
      0.8 GHz/0.80V 26.9C + 5.9C 033.3% 057.1% 047.2%
      ...etc...
      0.0 GHz/0.00V 21.0C + 0.0C 000.0% 000.0% 000.0%
      The article should have stated:
      "For a 66% drop in speed, there was a 53% drop in added temperature."
      "a 43% drop in voltage produced a 53% drop in in heat seems more reasonable."

      My observation from that data above:
      "A drop of only 400MHz (17%) and 0.15V (11%) showed a significant drop in the amount of heat generated (25%)."

  • There is a point... (Score:4, Insightful)

    by chihowa ( 366380 ) on Saturday June 04, 2005 @09:46AM (#12723302)
    On all of my personal must-stay-up servers, I get a processor that is too beefy for the task it's to do, then clock it down. It's usually rock solid and runs very cool. In some cases I've been able to get by using only passive cooling and still keeping the processor very cool, making the system solid, cool, and nearly silent.
  • ...running a server on 486DX80 downclocked to 66MHZ. Original fan+radiator replaced with a radiator alone. From an Athlon.
    (several more power savings in the system - like not using a CD drive, and the power supply runs just fine with its fan switched off. So, a fanless config.

  • I know a way (Score:3, Funny)

    by Shinaku ( 757671 ) on Saturday June 04, 2005 @09:48AM (#12723309) Homepage
    If they want to underclock a 4000+, they could just swap me my 3000+.. I wouldn't complain.
    • I think the question remains: Is a 4000+ underclocked to 3000+ more reliable or efficient that the 3000+ would've been in its place: the 3000+ definately costs less.
  • That's what CPU power management is for: it allows you to select in software what tradeoff between performance and power you want. I believe most (all?) of my desktop machines have it built in.

  • Faulty Analysis? (Score:5, Insightful)

    by Brian Blessed ( 258910 ) on Saturday June 04, 2005 @09:51AM (#12723330)
    The temperature measurements in the article don't seem to be relative, and yet they say things like this:
    for a 66% drop in speed there was a 20% drop in temperature.

    In this context, talking about a 20% drop in temperature in degrees celsius makes no sense for comparison purposes. They go on to state that "a 43% drop in voltage producing a 20% drop in heat seems more reasonable", but this is assuming that the temperature drop corresponds to a equal reduction in heat output.

    - Brian.

    • Frequency is proportional to heat, since frequency is proportional to the active power component (~1/3rd the total power). The slope of the proportion is determined by the cooling solution, which can vary from OEM to OEM, even from box to box from the same OEM.

      So the article is correct. There is a proportional relationship between frequency and temperature, just not the same for everyone.

    • Re:Faulty Analysis? (Score:2, Informative)

      by CTho9305 ( 264265 )
      For simple linear devices (like resistors), power = V^2 / R, i.e. it changes with the square of the voltage. Halving the voltage quarters your power.

      For CPUs, a better model is P = C*V^2*F (capacitance times voltage squared times frequency). If you halve the voltage and halve the frequency, the [dynamic] power drops by a factor of 8. Unfortunately, modern transisots leak, so you probably won't actually see that much drop, but the point is, underclocking even a little can result in huge power savings.

  • Bragging rights... (Score:3, Funny)

    by Alsee ( 515537 ) on Saturday June 04, 2005 @09:52AM (#12723332) Homepage
    ExXXtreem underclocker bragging rights post...
    I've got my system cranked to 200 millhertz!*
    Beat that ya loozers!

    * Footnote: No system stability problems detected yet.
    I'll post a confirmation follow-up when the standard stability test suit finishes running.

    -

  • Mistake (Score:3, Insightful)

    by Richard_J_N ( 631241 ) on Saturday June 04, 2005 @09:52AM (#12723335)
    They have measured the (absolute) celcius temperature of a well-cooled system, without quoting the ambient temperature. Then, concluding that the temperature hasn't droppped much, they assume the power hasn't dropped much.

    The correct measurement is the *difference* in temperature between the CPU and the ambient air. Power dissipation is linearly proportional to this.

  • Underclocking for Gaming, Reverse Logic (Score:2, Interesting)

    by Anonymous Coward
    From 99-03 I always underclocked my AMD CPUs for gaming, the minimal requirements necessary for playing everyones favorite Counter-Strike, and my undying urge to make my CPU last ages kept my system running smooth, my latest underclocking was from a 2800+ 2ghz AMD down to a 1.87ghz miracle machine that ran on a minimal fan system, never overheated and my record uptime was 3 months and 2 weeks ;D

  • Use CrystalCPUID to manage speed and voltage (Score:5, Informative)

    by Brian Stretch ( 5304 ) * on Saturday June 04, 2005 @10:16AM (#12723442)
    Use CrystalCPUID [crystalmark.info] to manage your AMD64 CPU's speed and voltage rather than the default Cool 'n Quiet power management (set your Power Scheme to "Always On" to disable that, definitely leave the CnQ driver installed). On most HP AMD64 notebooks we've found that you can usually safely set the core voltage at about 0.2V below stock at full speed. Judging by the AMD Thermal Design Guide, that's enough to cut power consumption nearly in half. I swapped in a Mobile-class Athlon 64 3200+ into my Pavillion zv5000z in place of the stock DTR-class chip and have been running 1GHz at 0.8V, 1.6GHz at 1.025V, and 2GHz at 1.225V for months. That puts the full speed power consumption at slightly above AMD Turion ML levels. For the stock DTR chips, 1.3V at full speed is popular.

    Of course, in average use, the standard AMD Cool 'n Quiet behavior of running 800MHz at 0.95V while idle will give you battery life that's almost as good as an undervolted setup. 3-4 hours of battery life with a 12 cell battery is common, versus a fraction of that for the poor bastards who bought the P4-based zv5000 series (HP wisely dropped Intel CPUs from their zv6000 line). Undervolting does wonders under heavy CPU load though.

    MobileMeter [geocities.co.jp] is my favorite way to monitor CPU speed and temperature, and Hot CPU Tester Pro [7byte.com] verifies that I didn't go too far.
  • Doesn't using CPUFreq with a powersave governor have the same effect as underclocking the CPU in the BIOS? What's the advantage of doing it the way suggested in the article?
    • the cpu can only go within some ranges. Like mine can go from 1.5v @ 2.2Ghz down to 1.1v @ 1Ghz ... what if you want to run at 0.9v at say 500Mhz? ...

      But at that point if you have to reboot to go into "powersave" mode ... just buy via box or something.

      Tom
  • I usually underclock my servers here when I expect them to be left alone/unattended, such as in a phone closet, and just expect them to be always up. Most tasks are not that compute bound, especially not the ones I might typically setup a small server for, such as an internal file server, internet packet routing, or a phone control system.

    The benefit for heat reduction (and less thermal sensitivity in an enclosed space) is often a worthwhile tradeoff over a server I can just leave alone and expect to run

  • Isn't this what CPU Frequency Scaling [amd.com] is for? I personally use the ondemand scaling governor made available in linux kernel 2.6.10, I believe.

  • screw the fans, all i hear is hard drives! (Score:4, Informative)

    by iamhassi ( 659463 ) on Saturday June 04, 2005 @11:02AM (#12723713) Journal
    Seems all these articles whine about how "loud" the 80mm fans are. Well there's plenty of instructions out there explaining how to run fans at 5v instead of 12v, significantly reducing the sound to the point that even generic fans are inaudible.

    what I don't see very often is reviews address all the other sounds in a case, like the damn hard drives. I never hear my fans, system is water-cooled with two 120mm fans at 5v, but all nite all i hear is GRINNNNNNNNNNNNNNNNNNNNNND of the damn hard drives. Why doesn't someone address this issue and do a REAL review on how to get rid of hard drive sounds? Sure silentpc has done a few, but everyone else is like "yeah, i hear like, a fan, sometimes, so i'm gonna run my new 4000+ processor at 800mhz".

    talk about unoriginal....

  • Computers built for industrial temperature ranges are routinely underclocked. We have three underclocked Pentium 4 systems in the Overbot [overbot.com]
  • A couple of years ago, I took part in a project to build desktop PCs for low income families with high-school age kids.
    We made about 200 total boxes. When we got towards the end, we had about 3 dozen donated motherboards that could only be set to a max of a 450 Mhz processor and PC 100 DIMMs for RAM, but had 2x AGP slots, and a bunch of P2-500 and 600 CPUs, PC 133 RAM, and single speed AGP video cards to match up. We ended up turning out a bunch of machines that were all basically underclocked in severa

  • Makes complete sense in large data centers (Score:3, Insightful)

    by micron ( 164661 ) on Saturday June 04, 2005 @11:42AM (#12723974)
    I am extremely glad to see "underclocking" gaining in popularity.

    I design systems that run applications across hundreds or thousands of servers. Many of my applications are bound by items such as connections, long before processor becomes a bottleneck.

    As a case example, I will have an application that utilizes 55% of the proc across two processors. I use two processors to keep response time down (multi threads). Intel gives me a new processor. I get to spend more money to power the new processor, but now I get the amazing advantage of the new, faster, more power hungry machine now being 30% utilized.

    More money down the drain, but I am not getting much for it. The worst abuse of this is static content web servers. I run into connection issues and network latency issues long before I run out of processor.

    With the new HE processors from AMD, I can turn down the processor clock and cut my power consumption by as much as 50% across the board. This translates into real savings on power and cooling infrastructure.

  • For any CPU's manufactured on 90nm or some fine geometry, there's not much point in under-clocking.

    The leakage current from the transistors makes up the bulk of the power draw. It can be 90% or even higher.
    (The static current drawn is when you just turn on the power and don't apply any clocks or toggle anything).

    So at best, even if you clocked it to 0MHz, you'd save maybe 10% power if you're lucky. That's it. It's not worth it.

    You can get better power savings if you completely shut off portions of the ch

  • I already did this back in 1980..... (Score:4, Interesting)

    by panurge ( 573432 ) on Saturday June 04, 2005 @11:58AM (#12724047)
    Any other older-timers may remember the already very slow RCA 1802 CMOS processor. I used one of these in a home-made portable EPROM programmer, which allowed you to enter data from a keypad to make tiny patches to tiny machine code programs. To increase battery life, the thing was clocked using a 2MHz crystal (enough for the eprom programming) but when it wasn't burning, it ran on a 20KHz clock which was enough for the keypad data entry. The result was a power consumption in the low hundreds of microamps when idle, rather than 10mA or so. To those who say, why not just turn it off? I have to explain that in those days flash memory came in units of 64 expensive bytes. The battery power was necessary to keep the CMOS static RAM alive.

    Thank you for letting me share this old-timer drivelling on slashdot.

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