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Typical mains power for mid-range PC?

Discussion in 'AMD Overclocking' started by Jon D, Jul 21, 2006.

  1. Jon D

    Jon D Guest

    How much mains power does a modern systen unit need?


    In more detail ... I am in the UK.

    My existing PC (socket-A 462-pin cpu with 768 MB SD-RAM) uses about 180
    Watts at 240 volts of which about 65 or 70 Watts is to power my CRT.
    Printers and scanners would be extra.

    Modern cpu's seem to be quite power hungry.

    QUESTION: Approx how much mains power is likely to be needed for a
    modern mid-range AMD-based PC? I don't know the existing AMD processors
    but something average to middling is what I mean.

    QUESTION: Would a sysem based on an Intel cpu need less power?
    Jon D, Jul 21, 2006
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  2. Chip power consumption figures are published by their manufacturers.
    =?UTF-8?B?UGFsaW5kcuKYu21l?=, Jul 21, 2006
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  3. Jon D

    Gerard Bok Guest

    Trust me, they will require the same amount of power, wherever
    you are. Only the pricetag will change.
    65 to 70 is very decent for a CRT. If you want to save in this
    field, look for a TFT.
    Modern users are (CPU-)power hungry.
    There is no free lunch, not even in processor-land.
    You need to put energy in to get anything out.
    There is no middling. Depends on how your PC is built and how you
    use it. Some PCs switch down their CPU on low loads. But that
    wouldn't do any good if you keep your PC busy.
    No. Generally speaking, Intel is not your choise if you want to
    conserve energy.
    Gerard Bok, Jul 21, 2006
  4. Take a look at the Core-2 processors, such as the E6400.
    =?UTF-8?B?UGFsaW5kcuKYu21l?=, Jul 21, 2006
  5. Jon D

    Johannes Guest

    Nonsense, there is no generalisation! Intel has power hungry Prescott
    P4 and derivatives and low power Pentium M and very power efficient
    new generation Core 2 Duo (Conroe); the latter is the way to go for a
    new system.
    Johannes, Jul 21, 2006
  6. How much mains power does a modern systen unit need?

    o P-3 -- 30-35W
    o P-M -- 25-35W
    o P4 Celeron 2.0 -- 58W
    o P4 3.2Ghz 800fsb HT Northwood -- 82W
    o P4 Prescott -- 115W+

    o Onboard -- 10-20W for low end, 50W+ for higher end
    o Add in Card -- 10W for low end, 100W+ for high end

    o 1GB in 1 DIMM consumes 10W, generally assume 15W
    ---- so an 8GB PC is needs a RAM-VRM able to supply >100W
    o 1GB in 4 DIMM can consume 30W or more
    ---- RAM slots historically limited as much re RAM-VRM Watts

    o 7200rpm 3.5" -- 10W at idle, some more, 20-25W maximum
    o 10000rpm 3.5" -- assume 30W re cooling needs

    o Writing -- 25W a typical benchmark figure (a lot really)

    Ensure MS File Indexer is not running in the background, or spyware.
    Either can cause an elevated baseline power usage.

    For systems...
    o Base end office Cel2.0, integrated graphics, 1 HD, 1 optical
    ---- idle -- 85W with 17" TFT, 95W with 19" TFT
    ---- load -- 120W for 17" TFT, 130W with 19" TFT
    o Apple Dual G5, multiple HDs, 20" TFT, optical, 4GB
    ---- load -- 325-350W
    o Dual Xeon, multiple HDs, 20" TFT, optical, 4GB
    ---- load -- 450W

    If you are using a CRT, an equivalent TFT is uses 70% less watts.
    A 21" CRT is around 95-115W, a 19" TFT is around 35W (the big
    factor in TFTs is how bright you have the backlight obviously :)

    As for upgrading just for energy saving, the payback period would
    be longer than the actual energy saved even if run 24/7 at full load.
    Core 2 Duo are essentially a "desktop P-M" re efficiency, but the
    boards are very expensive as are the CPUs (compared to lower end).
    Good value versus a Mac G5, not good value if just to save watts.

    If not being used, at least power the CRT/TFT off and ensure
    no screen savers running keeping the CPU from idling.

    Athlon XP, Northwood P4 have a quite low idle wattage.
    Prescott P4 by comparison have a very high idle wattage (50W+).
    Dorothy Bradbury, Jul 21, 2006
  7. Jon D

    kony Guest

    It'll be close enough to what you already have, maybe 10W
    more on average.

    Depends on what you buy. Averaging Intel's entire line of
    CPUs including Core 2 Duo, it'll be close enough to the AMD

    Intel's newest CPUs use less power but then their chipsets
    use more, and then they want to focus on performance per
    watt instead of watt per system. Nobody buys 1.3 systems so
    it has to be performance per system if the important factor
    is how much power a small number of systems uses.

    In short, ignore power usage on normal (equivalently
    equipped) desktops, if power usage is that important then
    neither choice is suitable.
    kony, Jul 21, 2006
  8. Jon D

    Cuzman Guest

    Jon D wrote:

    " How much mains power does a modern systen unit need? "


    " My existing PC (socket-A 462-pin cpu with 768 MB SD-RAM) uses about
    180 Watts at 240 volts of which about 65 or 70 Watts is to power my CRT.
    Printers and scanners would be extra. "

    The CRT, printer and scanner should have their own power units
    independent of the PC's PSU.

    Make a list of everything that isn't powered by the PC's PSU. Find the
    specs on the manufacturer's websites and add them to the total wattage
    you need for the PC PSU (see aforementioned link to calculator). Work
    out the total wattage, divide by 1000, then times by 0.0633 (averagely
    high cost of electricity) . That will tell you the approximate maximum
    costs to run your PC each hour (in £s).

    By that logic, a total of 470W would cost less than 3 pence per hour (
    (470 / 1000) * 0.0633 = 0.029751)

    Cost of electricity: http://www.ukenergy.co.uk/pages/calculation.html


    Bear in mind that, in reality, the cost will be considerably less than
    that, as much of the setup would not be running constantly and under duress.

    " Modern cpu's seem to be quite power hungry. "

    Yes and no. It depends how you look at the argument. They have more
    capabilities than previous generations of CPUs, but big steps have been
    made in nanometre architecture. From the dawn of the Athlon XP the
    process has gone from 180nm to 130nm to 90nm and now towards 65nm.

    If you were to re-encode the same 2 hour video on both an Athlon XP and
    an Athlon 64 X2 you would find that the Athlon 64 X2 would be using more
    power, but it would also do the task considerably faster. If a system
    uses twice the power, but does the task in half the time, what's the
    difference? You would only end up using more power by using your PC
    more (which often becomes the case)

    Modern systems can use considerably more power for games because the
    graphics cards and CPUs can output more frames per second (FPS). If
    everyone set their systems to limit the FPS they would find their power
    usage to be lower. However, most people don't do this, allowing their
    systems to use as much power and capability as their components will
    give them.

    DDR2 actually uses less power than DDR(1), but yet operates at higher

    Another area of power consumption has been the rise in spindle speed for
    hard drives. The rise from 5400rpm to 7200rpm has been a large factor
    in power increases, and many people even have 10,000rpm hard drives in
    their desktop systems now. However, as with other components, steps
    have been made to limit the power used by read/write operations.

    One other big factor is the move towards Active PFC (Power Factor
    Correction) in PSUs. http://www.endpcnoise.com/cgi-bin/e/pfc.html

    " Approx how much mains power is likely to be needed for a modern
    mid-range AMD-based PC? I don't know the existing AMD processors but
    something average to middling is what I mean. "

    Mid-range means different things to different people. CPU speeds often
    dictate how "modern" a PC is, but everyone has different requirements in
    their RAM requirements, graphics card usage/capabilities and the
    size/number of hard drives they wish to use. Everyone also has
    different amounts of add-on equipment and other stuff.

    " Would a sysem based on an Intel cpu need less power? "

    Not necessarily. Intel came under some criticism because their 90nm
    desktop Prescott CPUs used more power than the equivalent AMD CPUs which
    were still at 130nm. However, Intel have had more success recently with
    65nm, and it's not like all Intel CPUs use more power than all AMD CPUs.

    If you're that worried about power consumption you could opt for a 35W
    Athlon 64 X2 3800+.

    You'll find that article quite interesting where it states the total
    power output under load as being 82W, but don't think for a minute that
    you only need use a 100W PSU. In the review above they use a 500W
    CoolerMaster iGreen.

    With the following components you could have a gaming PC that will
    certainly last for a couple of years (or even longer), and which uses a
    little less power than the comparable systems:

    - AMD Athlon 64 X2 3800+ 35W AM2 ADD3800IAA5CU
    (see previous review)
    - Asus M2N32-SLI Deluxe motherboard
    (just because it's currently the best AM2 motherboard)
    - Corsair XMS2 2x1GB DDR2-800 TWIN2X2048-6400
    (1.9v operating voltage is low for DDR2-800)
    - Nvidia GeForce 7900GT 256MB
    (hits a sweet spot with power/performance
    http://www.vr-zone.com/?i=3335&s=8 )
    - Seagate Barracuda 7200.10 320GB ST3320620AS
    (lots of storage, sweet spot in price, reliable, 5 year warranty)
    - CoolerMaster iGreen 430W RS-430-ASAA
    (see aforementioned link to CoolerMaster website)

    ....and just as important, add an LCD TFT monitor.
    Cuzman, Jul 21, 2006
  9. |> How much mains power does a modern systen unit need?
    | Dorothy Bradbury

    very nice post, good work
    david schwerbel, Jul 21, 2006
  10. Jon D

    John Jordan Guest

    Numbers culled from many years of review-analysis:

    idle load
    AXP 2800+ (Barton) 45W 70W
    A64 3000+ (130nm) 20W 60W
    A64 3200+ (90nm) 10W 30W
    A64 X2 3800+ <20W 50W

    These figures are for the CPU itself, quoted without CnQ, which roughly
    halves idle power. Note that ATX PSUs are usually inefficient at <100W
    power draw, so as much as 30-50% of mains power may be wasted in the PSU.

    As for Intel, Prescott-based CPUs use much more power per core at both
    idle and load. The new Conroe cores appear to use more power at idle but
    less at full load than the X2s. SOI does still appear to have an idle
    power advantage.

    You can get a whole Sempron-based VIA IGP system box into less than 60W
    idle mains draw. Less than that is difficult because of PSU
    inefficiency. If you add an nForce4 chipset and a decent video card,
    mains idle power consumption will approach 100W.
    John Jordan, Jul 21, 2006
  11. Jon D

    Rod Speed Guest

    It overstates the power consumption of some items considerably.
    Rod Speed, Jul 21, 2006
  12. It overstates the power consumption of some items considerably.

    Such as?
    Dorothy Bradbury, Jul 21, 2006
  13. Jon D

    Rod Speed Guest

    Hard drives are one obvious example.
    Rod Speed, Jul 22, 2006
  14. It overstates the power consumption of some items considerably.
    For HD I stated...
    o 7200rpm 3.5" -- 10W at idle, some more, 20-25W maximum
    o 10000rpm 3.5" -- assume 30W re cooling needs

    7200rpm 3.5" manuf'r specs...
    o Current hard drives
    ---- smallest capacity -- 7.50W idle, 12.5W active
    ---- largest capacity -- 9.30W idle, 13.3W active
    ---- variable quality -- 8.10W idle, 13.6W active
    o Older HDs can have somewhat higher figures
    o Overall I would still take 10W at idle, 20W max if older HD

    10000rpm 3.5" manuf'r specs...
    o Current hard drives
    ---- high performance actuator -- idle 7.9W, 8.4W active
    ---- very high performance actuator -- idle 12.2W, 17.4W active
    o Trends
    ---- 1) higher performance actuators to justify price premium (watts)
    ---- 2) silicon disks forcing higher cache on electromag disks (watts)
    o Overall I would still assume 30W re cooling needs

    In terms of energy usage the confounding factor in PCs is not the
    HD/RAM/Optical or even CPU (P4 Prescott 115W v Conroe 50W).
    It is the actual GPU fitted - integrated may be 10W, whereas a high
    end card can draw well over 100W & idle not far off that figure.

    Saving 50W by choosing a very pricey m/b & chip does not gain
    much if you also u/g the graphics card to one drawing 50W more.

    Likewise a CD-ROM may draw only a few watts, but a high end
    DVD-R/RAM/CDR writer multi-drive can draw 18-25W at peak.
    Yes CPUs can draw a lot of power - but so do other devices.
    Dorothy Bradbury, Jul 22, 2006
  15. Jon D

    Dylan C Guest

    My setup at 50% CPU load and HD read/write pulls ~245 Watts (as reported
    by my UPS). System specs below.

    -Abit AV8
    -AMD64 X2 3800+ (overclocked but stock voltage)
    -512 MB of PC3200
    -3 IDE HDs + 1 USB External
    -Idle DVD-R
    -17" CRT
    -80mm System fan
    -GeForce3 Ti200 AGP (active cooling)
    -Antec 420W PSU

    *Other Items pilling power from same UPS
    -Cable Modem & Wireless Router
    -HP All-in-One (idle)
    -2.1 Speaker system (idle)

    Based on these numbers, I would assume that my actual PC pulls ~200
    watts or slightly less. Its not a gaming rig, but the most likely
    upgrades (more RAM and newer AGP card) would likely add less than 50 Watts.

    While a quality power supply of the proper wattage is very important, I
    would venture that most users need less than 300 Watts and very few
    require more than 400. Keep in mind that I've no experience with more
    modern/power hungry video cards.

    -Dylan C
    Dylan C, Jul 22, 2006
  16. Jon D

    Rod Speed Guest

    And that is overstating it.
    And that is too.
    Bad assumption.
    Those are overstated on the idle.
    God knows what 'variable quality' is about.
    Pity that none of the other numbers are with older hardware.
    Nothing like your previous 30W
    More fool you.
    That last is a good example of the problem with your
    original and you didnt even mention the AMD cpus.
    Again, nothing like your original.
    Having fun thrashing that straw man ?
    Not very often tho.
    Rod Speed, Jul 22, 2006
  17. Jon D

    John Jordan Guest

    Easily tested. Put PC on wattmeter, test idle with one drive. Add second
    7200rpm IDE drive, test idle and folder-copy (within second drive),
    subtract to get difference.

    With a 120GB Maxtor plus-9 (from the "probably dying" pile), I get:

    idle: 10W
    load: 24W

    Note that these are mains-side wattages, so they include PSU
    inefficiency. Idle is spinning-idle, as hardly anyone spins down
    non-laptop drives.
    John Jordan, Jul 22, 2006
  18. Jon D

    Rod Speed Guest

    Not really, most dont have any way of measuring the power their PC takes.
    Thats nothing like typical for 7200 rpm drives.
    And neither is that.
    So arent relevant to Dorothy's numbers.
    Unlikely given that most modern OSs default to spinning them down.
    Rod Speed, Jul 22, 2006
  19. Jon D

    John Jordan Guest

    It's an extremely common drive (at least in the UK), and far from the
    most thirsty (I have an early 7200rpm Seagate somewhere that uses around
    twice the idle power). My 120GB Seagate has similar idle consumption to
    the Maxtor but somewhat less load.
    Dorothy didn't explicitly state whether the wattages in the original
    post were mains or PSU-side, and you never asked. The typical difference
    would be around 30%, in case you care.
    XP's defaults for desktop machines are:

    Monitor standby: 20mins
    HD spin-down: Never
    John Jordan, Jul 22, 2006
  20. Jon D

    Rod Speed Guest

    Most current drives dont idle at 10W.
    Dont believe it, list the model number.
    That was obviously implied. And should have been
    obvious from the Prescott cpu number cited.
    I dont, because that wasnt what her numbers were about.
    Rod Speed, Jul 22, 2006
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