Since you've tested your scheme by hand (unplugging the
power cables), you should be fine.

As for safety, the hard drive takes 5V and 12V, so there should
be no personal safety issues.  (In any event, any decent
commercial switch won't expose you to the power going
through it.)

And as for the hard drives, it is true that the atx power supply
always (when plugged in, but not turned 'on') provides a
special 5V 'stand-by' power source, but the main power
cables (including the 5V/12V four-wire cables that go to
your hard drives) are only powered after the atx supply
is turned on.

If you only switch your hard-drive switch back and forth
when your computer is 'off', you won't be 'shocking' your
hard drives --- when you turn your computer 'on', which
ever hard drive is active will get the same controlled
ramp-up of the 5V and 12V wires that it would have
gotten without your custom switch.

(Switching your hard-drive switch back and forth while
your computer is 'on' would not be a good idea --- it
might have the potential to damage the drives.  So your
scheme is not completely idiot proof --- it relies a bit
on the discipline of your 'users'.)

Let's us know how it all works out.


Ultra <[log in to unmask]>

> It seems like I need to repeat something. I have A7V, it has Promise ATA100
> controller (right now empty) and standard ATA controller, therefore, there
> are two primary controllers. When I said switch, I did mean switch off HDD
> power, so both win98 and win2k HDDs are C: drive. They will never see each
> other because only HDD contains either win98 or win2k can get power, not
> both.
>
> The "switch" should work perfectly, I "used" it before (unplug power by
> hand) for troubleshooting and avoid problem during upgrade (I'm still using
> it now).
>
> The reason I need a switch, not software solution or a removable HDD kit, is
> that: I don't have free 5" bay (no space for removable kit), I already have
> win2k on HDD (format and install win98 first, win2k second not "possible"
> now), I don't use Boot Manager software (eg. Partition Magic) myself for
> personal reason, and plug/unplug power too often will damage the HDDs.
>
> The thing I worry about most is safety, I don't know if the switch is safe
> enough to not create "shock" when I switch it on or off, I know ATX power
> supply always has power go through (unlike AT power supply). If I "shock"
> HDD so often, I'm worried I will kill my HDD.
> > ...
> > >What's your plan?...
> > > ...
> > >If I were you, I think I would test this scheme before investing
> > >the time in building a switch.   (Just do it by hand, by detaching
> > >the appropriate power cables, and try rebooting.)
> > ...
> > The biggest problem I see in this... is that, if I'm not mistaken,
> whatever
> > drive your booting from, the system must boot from the primary master. You
> > may be able to boot from a floppy, switch to the Win98 drive and type win
> > <enter>. This is still questionable. Next time I install Win98 on my test
> > machine, I'll see if I can install to, say.... D:\windows

     Frank R.Brown
     Frank.R.Brown@MailAndNews

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