The switch part should be easy, but the overall idea seems
to me to be a little dicey.

My concern is that you will have unpowered hard drives
connected to your controller.  There certainly doesn't have
to be anything wrong with this, but I'd be surprised if the specs
say that this has to be supported.  (And if the specs don't
require it, I'm sure some hardware manufacturer somewhere
will have cut some corner that keeps it from working.)

Let me suppose you have ide drives:

What's your plan?  You could put the two w2k drives on
your primary controller, configured as master/slave, and
put your w98 drive on your secondary controller.

Now you have to assume that when you power down your
w2k drives, the bios will boot from your w98 drive, even
though the w2k drives are still attached.  (You also have
to assume that the unpowered drives won't mess anything
up by just being there.)

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.)

If it works reliably, making the switch should be easy.

I'm assuming your hard-drive power cables are those
5V / 12V four-wire jobs.  (Red +5V, yellow +12V, 2 black
ground wires.)

You need a double-pole, double-throw switch.  Run the ground
wires straight through (i.e., they bypass the switch altogether),
and run the red and yellow wires to each of the two poles,
respectively.  Throw the switch one way, and the power comes
out on set of red and yellow output wires; throw it the other
way, and the power comes out a second set.

You could wire the switch up in a separate little box, and put
in on top of your computer, or, if you can find a free spot on
your case (front panel would be best), you can mount the
switch directly on the case.  I would look for a switch that
can be mounted in a single round hole.  Then mounting is
very easy --- all you need is a drill bit of the right size.
You drill the hole, slide the switch through the hole from the
back, and attach it by screwing down a nut from the front.

The voltages are low, and the current drawn by the hard drives
is moderate, so it should be easy to find a switch that can
handle it.

Good luck.


Ultra <[log in to unmask]> wrote:

> ...
> I'm having an idea for my perfect dual-boot system. What I will need is a
> "Harddisk switch", which I can choose which harddisk got power. So that I
> can add another harddisk to my win2k machine, when I need win98, I can shut
> down win2k, "switch" harddisk to win98 HDD -> boot into win98 ... I don't
> want Boot manager software solution for personal reason. I also can't afford
> to mess up my win2k, so I don't want to "trick" win2k boot record around,
> just in case if something goes wrong...
>
> I know I need to make the switch myself, but I'm not sure which way/design
> is the best, and how to attach the switch to case (it's not important, but
> I'd like it looks good rather than bad) - I'm running out of both 3 & 5 inch
> bays.
>
> Here is how I want the "switch" to work:
>
> HDD1 \
>               -- for win2K --\
> HDD2 /                          \
>                                          >-------HDD Power Switch
> HDD3 --- for win98 ----/
> * when win2k is running, HDD3 has no power, when win98 runs, HDD1 & HDD2
> don't get power.
>
> Could anyone give me a good design?

     Frank R.Brown
     Frank.R.Brown@MailAndNews

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