[NCLUG] Linux on Sun Hardware

[Michael Dwyer]

Jim Wildman wrote:
> 
> No.  Some switching supplies won't pull anything (except fan) until
> they have a load.  They might have a spike, but I've never seen one
> pull full load when the load does not exist.  (visions of opamps,
> capacitors, resistors, and transistors dance in my head).  I had
> to breadboard a +/- 15V current limited switching power supply during
> an EET lab.

Yeah, right now we're looking to wire up 140 Pentium ~90 computers here
at the office.  Each nameplate says 3 amps.  Unfortunatly, our
electrician has to believe that.  But I hooked one up to a meter, and I
only saw, like, one tenth of that.  I expect the startup is a little
steep, trying to spin up those ancient drives... but I strongly believe
that there is no way those things are drawing 3 amps each...

FWIW, if I read things right, a basic voltage regulator always pulls its
rated amperage, even when it is not loaded...  Does that sound right? 
It doesn't to me... But anyway, that might be where the confusion is
coming from.

So, could it be said that testing the draw of a power supply is a good
measure of load on the power supply?  That is, if I have a power supply
that is rated to 3 amps, and it is currently drawing two, is it safe to
assume that I can probably hang another drive off that power supply
without problem?

Finally, the Sun machines are SparcSTATION 4/330's.  You can see a
glamor-shot of one of the machines in question at this site:
http://www.obsolyte.com/sunPICS/sparc_vme/sun4_330.jpg