Hi.
        I can't resist to put here the electrical explanations which
makes this something impossible to solve.

> On 11 Jun 98 at 7:43, Eric Sabo wrote:
>
> > How many things(peripherals) can you put on one 250-300 power
> > supply?

>   I've never been able to support this mathematically, but my rule of
> thumb has been that each "drive power lead" from the power supply can
> handle one hard drive and one other device (floppy, CD-ROM, fan, or
> whatever).

        Internally, on the power supply, all cables of the same color are
soldered to the same big point. So cascading cables, other than lowering
reliability due to serializing connectors, is possible.

>   I've encountered some really strange problems whenever I have put
> two hard drives on one lead -- usually exhibiting the classic
> pattern where warm boot usually works fine and cold boot never does.

        The thing is that all electronic components have something
called "Absolute Maximum Ratings", one of them being the power consumption.
It happens that is you sum up the max power consumptions of all the
components, you reach an unfeasible enormous figure. So what is done
usually is take a statistical big number, but not the sum of all max's.
        But then comes something worse: the transient start-up of the
mechanical components (disks and related), which places a heavy demand
on the +12V, which in turn demands from the whole power supply, and
probably is not fully specified in the components and the power supply.
So the worst case is when turning on the equipment.
        My opinion is that the power supply specs (250-300W) give you
an orientation, but not much more. And, are they real?

>   I think Drew Dunn recently posted a URL to his page which includes
> a machine with a mini-tower case being used as an external drive
> enclosure.  That, or something very like it, is what I'd recommend
> for going beyond two (SCSI) hard drives.
>
> David G

        This is a good idea, but rather I would take a full tower, place
two power supplies within it, and join their grounds at a single point,
ideally opening them and soldering.


************************************
Javier Vizcaino. Ability Electronics. [log in to unmask]
  Starting point:        (-1)^(-1) = -1
  Applying logarithms: (-1)*ln(-1) = ln(-1)
  Since ln(-1) <> 0, dividing:  -1 = 1     (ln(-1) is complex, but exists)