Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!samsung!munnari.oz.au!cluster!wolfen!david
From: david@wolfen.cc.uow.oz (David E. A. Wilson)
Newsgroups: comp.sys.mac.hardware
Subject: Re: ADB and blown motherboards
Message-ID: <6197@wolfen.cc.uow.oz>
Date: 3 Mar 90 06:39:37 GMT
References: <1494@key.COM>
Reply-To: david@wolfen.cc.uow.oz.au (David E. A. Wilson)
Organization: Uni. of Wollongong, NSW, Australia.
Lines: 18

In article <1494@key.COM> jbr@hongkong.key.COM (Jeff Rubin) writes:
>phrase it in terms of my Mac IIcx.  The keyboard (Apple extended)
>has a button with a triangle on it that I use to turn the power
>on.  Since the keyboard is an ADB device, does the power-on
>mechanism use the ADB?  If so, does this imply that ADB has power
>even when the rest of the machine doesn't?  Does that mean that it
>is not safe (just as unsafe?) to plug/unplug ADB devices when the
>power is off?  Do I have to pull the plug from the wall before it
>is safe?  Is there a big capacitor on the power bus?  How long do
>I have to wait after I pull the plug from the wall?

At least with a Mac II, if you unplug the power lead and then hit
the <| button the machine starts to power up and then comes to a halt
(even the hard disk starts to spin up & then stops).

From this I deduce that either the power supply capacitors or the motherboard
batteries supply power to the keyboard and enough circuitry to turn on
the power supply to the rest of the Mac.