Power consumption of dvd drive

Discussion in 'PowerPC Macs' started by rpaloalto, Nov 6, 2008.

  1. macrumors 6502a


    I have a pioneer 111d drive that is in a external enclosure,that I don't use anymore. I would like to put it in my mac pro. How much current do the drives draw when in idle or stand by mode.

    The only reason I ask. Is because, I have no need for a mac pro with two drives, as of now. I would be adding the second drive just because I can. I would pass on this if I new it was just sitting their wasting energy.
  2. macrumors P6


  3. macrumors G4

  4. macrumors P6


    haha im guessing it would, wher'd you pull that from i couldnt see it on the page i provided :confused:. peak power would be minimal compared to idle time, im guessing the idle time is more important, too bad i couldnt find it.
  5. macrumors 68020


    Well I sure can't imagine it taking virtually anything power-wise when idle. Since it is not constantly rotating like a hard drive does when it idles and there are not even any leds burning when it is not reading or burning, it may well approach (or actually reach) zero power draw. At any rate, even if it were drawing at the 15.6w burning power all the time (which it obviously would not be), it would be a pittance compared to the 155w at idle for an early 2008 8 core Mac Pro per Apple's Specs.
  6. macrumors 65816

    Which is again a pittance compared to mine, which draws over twice that at idle ;)
  7. macrumors 68020


    Yeah, that actually is very good point-- because they specified the 155w idle with a totally stock system with one 320Gb HD and NO PCIe cards, and operating in a 73F environment. I don't think I even want to know mine when it comes down to it now that you mention it! :D
  8. macrumors G4

    It's computed from the avg power.

    Avg. Power = RMS Power = (peak/(SQRT 2)). So just multiply the avg (RMS) by 1.414.

    The idle is needed for computing avg power draw. Kill-a-Watt is a nice way to cheat though. :p

    The peak values are important for determining the power draw at startup. If it exceeds what the PSU can handle (peak power), the PSU could self destruct, depending on how well it was built. :eek: ;)
  9. macrumors P6


    aaahh ok that makes sense, i didnt know you could calculate those sorts of things by using algorithms.

    yes peak powers is very important!!! the PSU wouldnt self destruct wouldnt it? i would just expect it to surge/brown out and turn off..
  10. macrumors 68020


    Well since Apple specs the Mac Pro as drawing a max of 12A at 110-120V AC ( http://www.apple.com/macpro/specs.html ), using the conversion of watts=volts*amps with a mid voltage of 115, it would appear that the power supply is spec'd to deliver up to 1380 watts at max load.

    Even with the earlier note that it is normally idling at somewhere around 155w (and 318w using 100% of the CPU power) and it would not be unusual for it to idle at maybe twice that with a full load of drives and PCI cards, it would still look to have plenty of headroom in the spec to cover pretty much anything you would want to do! So based on that, I would not expect the power supply to self-destruct. Now the wiring in my old house might be another matter perhaps- but not the newest Mac Pro PS. :D
  11. macrumors 68030


    I was in the same situation as the OP when I got my Mac Pro (except I had a 106D). Just put it in and enjoy your extra disc drive. :) The power consumption while not in use surely is negligible if not non-existent.
  12. macrumors G4

    Yes, they can self destruct. Sometimes in a puff of smoke for too high an instantaneous power draw. Others will glow cherry red and fail from overheating. Usually when the avg load drawn exceeds the avg rating, but not exceed the peak rating.
    No. That 1380W would be the actual draw from the wall, not what the PSU can deliver. Some of that power is lost to heat, and this is where the efficiency comes into consideration. Using avg, the efficiency is 980/1380 = 71%. Not very efficient at all, though there are others that approach this territory. Usually the cheap ones.
    As a general assessment, a 980W is just fine for a Mac Pro. You can't squeeze much into it. A full tower case, and that could be exceeded.

    Startup can be alleviated with certain features by other devices not part of the PSU. HDD's in particular. They may have a staggered startup capability, so all drives aren't attempting to start at the same time. It does help in cases of a large quantity of drives. Particularly RAID.

    But it's still better to assume such features don't exist, as their impact may not help by any notable difference, depending on specifics. Heavy graphics setups come to mind. ;)

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