G5 PowerMac Power Consumption - In Firewire Mode?

Discussion in 'PowerPC Macs' started by cosmichobo, Jan 27, 2014.

  1. cosmichobo macrumors 6502

    cosmichobo

    Joined:
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    #1
    G'day,

    As I understand (and telling by my power bills), the G5 PowerMac (in my case, dual 1.8GHz) is very power hungry. Made worse by the fact that mine only sleeps when I manually set it to, I figure it's cost me a fair bit of money over the years in utility bills...

    I've just upgraded to an iMac, but have 2x 1TB and 1x 320GB drives in the G5 that I don't currently have external enclosures to house them in. During the migration process I've just had the G5 running in firewire mode, but my question is, how much power does that use?

    Although I presume the processors etc aren't being engaged, the fans run full time (though not at 100% speed)... Is it more economical on power when in Firewire mode?

    Thanks

    cosmic
     
  2. eyoungren macrumors P6

    eyoungren

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  3. DeltaMac macrumors 604

    DeltaMac

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    #3
    I disagree
    The PowerMac is little more than a drive enclosure, the RAM is not occupied by any function, and the processors are not engaged. Fans run, because the power is on. The Firewire chip (whatever) is running, to provide the interface to the hard drives, and the part of the chipset that communicates to the hard drives is certainly active. Video is very minimal. So, power consumption would be low (compared to what your G5 is capable of doing)
    HOWEVER, I have never connected a power meter to any Mac while it was running in Target Disk mode - and if eyoungren has done that, and reports full power (whatever that might be on any Mac), then I'm wrong.
     
  4. Intell macrumors P6

    Intell

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    #4
    Power use would be higher than idel due to all the fans being in a fail safe maximum mode.
     
  5. eyoungren macrumors P6

    eyoungren

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    #5
    No, I have not done that. Don't even own one (but my dad is a former aerospace electrical engineer that designed guidance systems for ICBMs so maybe that counts?). :D

    I made an assumption, but I think it's an educated one. As Intell mentions the fans are at maximum. The documentation I've read online and elsewhere says that that is because there is no software controlling the fans speeds when you have the G5 booted that way. It also means that the processors are running at full power and are being supplied full power from the PSU simply because they are ON.

    What you indicate is plausible, but in the absence of fan control Apple opted to make everything ON at full blast in TDM simply because there was no way to regulate anything. And if you can't regulate anything on a G5 you have either on ON or OFF situation. Having the fans OFF while the processors are simply ON is a quick way to get a dead G5. It's either full power or nothing because in TDM there is no in between as nothing is regulating the system.
     
  6. DeltaMac macrumors 604

    DeltaMac

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    #6
    The fans run at high-speed because they are controlled by software, and in target disk mode, there's no software to control the fans, so they run at high speed. Not because of CPU load, or high temps, but simply that there's no software running to control the fans - so they default to protect the system, and NOT because of the load on the system

    I don't have any way to test this, and I can't even think of a method to test it - but I suggest that the CPUs are not operating at high load, and there's no high temps inside the case. Other than the fans (and drives, of course), there's no significant power draw by the PowerMac. The fan load would be, by far, the most significant power use in a PowerMac booted to Target Disk mode.
    Probably no real load on CPUs at all (where would CPU load in Target Disk Mode come from, anyway? )
     
  7. eyoungren macrumors P6

    eyoungren

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    #7
    OK. I'm not an electrical expert by any means (despite my dad). I know enough to be dangerous to myself.

    Since I am making assumptions based on my interpretations of what I've read I'm going to concede on this.
     
  8. Intell macrumors P6

    Intell

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    #8
    I just went ahead and tested my G5's power usage at three different operation modes. The lowest, was idle in Leopard at ~250 watts. The second lowest was Target Disk Mode with fans at lowest setting about ~380 watts. It only stayed in this mode for about a minute. The next lowest was in Target Disk Mode with fans at full at ~400 watts. The highest was 100% CPU in Leopard with fans at lowest setting at ~410 watts.
     
  9. cosmichobo thread starter macrumors 6502

    cosmichobo

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    May 4, 2006
    #9
    Thanks for all the replies, guys, and thanks for getting the voltmeter out, Intell!

    Interesting results, and pretty much answers the question... 50% more than at idle... only marginally less than full CPU load... Certainly not worth continuing long term. :( (I didn't think it would be sustainable, but is my only option for the time being.)

    Quick Q about the fans...

    When saying "100%" - to me that is how fast they run when using the Apple Diagnostic software, or (as happened to me) a CPU has issues and the fans speed up to protect the machine, sounding like a jet engine which you can hear from pretty much any part of your house!

    I had the G5 running for the past 36 hours or so in Target Disk Mode, and the fans were not running that fast. Certainly audible when walking up the hallway to my office, but not audible over the tv in the living room...

    Do the fans run at faster than "100%" when trying to protect the CPU??

    Thanks
     
  10. DeltaMac macrumors 604

    DeltaMac

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    #10
    Interesting, and more power consumption than I expected - thanks for the info.
    But, just curious - how does one change the fan setting in Target Disk Mode?
     
  11. Intell macrumors P6

    Intell

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    #11
    The fans cannot go above 100%. If they are not able to cool the CPU, then the G5 will either start NAPping or it will force shutdown to prevent damage. The fans run at a different speed for different models when the G5 in is Target Disk Mode. For the model tested, a June 2004 model, it is the same as when using AHT. When in Target Disk Mode, there is no way to change the fan speeds as they are in a fail safe mode.
     
  12. DeltaMac macrumors 604

    DeltaMac

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    #12
    But you did imply that there is different settings for Target Disk Mode (I have also never heard about fan settings in TDM, so just wondered why you chose to describe different fan settings, when none exist (other than differences between G5 models). It would help if you had noted that you did the tests with different Macs - that wasn't clear in your post.
     
  13. Intell macrumors P6

    Intell

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    #13
    The tests were all done on the same machine. When first put into Target Disk Mode, G5's don't have their fans up any higher than normal OS X idle. After about one to two minutes, they are at their maximum speed. The difference was put there to show how much power the 9 fans draw at maximum speed.
     

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