6 Replies Latest reply: Apr 14, 2006 1:43 PM by Old Toad
IlMolto Level 1 Level 1 (5 points)

I was just reading the "How to reset the SMU on a Power Mac G5 (Late 2004/2005)" page http://docs.info.apple.com/article.html?artnum=300341 and am now a little confused.

I own a Power Mac G5 (Late 2005), and every night before bed I turn it off and take the power plug out of the wall. In the instructions to resetting the SMU on a Power Mac G5, it states to remove the power cord from the computer for 15 seconds and then plug it back in.

By me always taking the power away from the computer, is this resetting the SMU every time? If so, can this cause problems?



Dual-core 2GHz PowerPC G5   Mac OS X (10.4.6)   1GB 533 DDR2 SDRAM
  • maclover Level 4 Level 4 (3,855 points)
    No, unplugging it shouldn't cause problems. But you may find the internal battery that retains the G5 settings (date, etc.) may not last as long as if you left the G5 plugged-in when shut down.

    If you are concerned that it uses a lot of planet unless unplugged, it uses about 2W - see para 5.1 here


    If you are concerned about night-surges, you could consider a surge-strip or a UPS. Hope that helps.
  • SlickRick Level 1 Level 1 (10 points)
    Don't do this if there is no problem with your G5. This is only if you had a kernal attack or major problems where your fans go off like an airplane. Usually thats a good indicator of a hardware problem. Check your memory if this is the case. Resetting the SMU requires you to push a little black button on the mother board to reset it to default. Plugging your computer on and off for no reason can only cause problems down the road.
  • IlMolto Level 1 Level 1 (5 points)
    Thanks for your replies,

    Reason why I unplug it of a night time is because I need to use the power point for my phone charger. It won't reach from the power board that my Mac is plugged into.

    If this is the case, I might have to re-position my room so I can have the phone charger and computer on at the same time.

    And what is that click sound coming from my Power Mac when I plug it and unplug it from the power point? Is this supposed to happen?
  • maclover Level 4 Level 4 (3,855 points)
    Presuming that you are referring to the 'relay click' sound when the G5 is first connected to mains power -

    I have not seen an Apple Official mention of this initial relay sound, let alone an explanation of what the initial relay does; but, over the course of two years in the G5 Usage forum, the absence of it is invariably bad news for the Power Supply Unit(PSU)(or other major bits). So - yes, it is supposed to happen.

    If you have no economic or environmental objections, and you can arrange for the G5 to remain plugged-in and the mains turned on, that should alleviate premature internal battery drain.

    Personally... I leave it plugged-in because the G5 is on a UPS, and also it would mean foraging in the jungle of wiring under the desk...

    BTW If you don't already - as the G5 is not on 24/7 the OS X maintenance scripts will not run; you may wish to consider running 'sudo periodic' from Utilities - Terminal occasionally - as explained in the thoughts of Dr. Smoke here


    Trust this helps.
  • IlMolto Level 1 Level 1 (5 points)
    Thanks guys,

    I might just leave my Mac on of a night time.

    ( :
  • Old Toad Level 10 Level 10 (131,550 points)
    I turn my Macs off at night but leave plugged in. Just get a power strip for your G5 and the phone charger.