> >     b) you can get 5V from the PS/2 connector if you need
> >        external power, so that might be an idea instead of
> >        really external power as you used. i don't know if it
> >        is enough though.
>
> Should be enough, but I wanted a replacement for the VM battery
> power, and with 5V it just says "Change Battery". Another point:
> not all systems are PCs.

The Amiga Diskdrive port has +5 and +12 lines, so you could grab power
from there
 

I just looked on the web at this page and it showed +12v, -12v outputs and audio in/out. The Amiga 1000 looks a little different: it has audio in and out, two clocks, +12, +5, and -5, and interrupt (in?) and a reset-out.

And of course, all RS-232 serial ports can provide power, just as long as you don't use too much of it(!). The standard output is +/-12v; minimum required output is +/- 3v, and many of the devices cheat a bit.
 

 
Or alternatively, just a standard 3.5" Hard drive power cable would
work (and is available on most systems) - you can buy cables designed
to double one plug to two drives, which could be adapted to a power vm
with passthru dongle.