[rescue] Netra 1100/1400 => 1105/1405?

[Greg A. Woods]

[ On Thursday, August 23, 2001 at 15:13:47 (-0700), James Lockwood wrote: ]
> Subject: Re: [rescue] Netra 1100/1400 => 1105/1405?
>
> The UltraSparc CPU modules do supply digital lines for CPU voltage, but
> the lines from the motherboards to powersupplies (on the U1/2/30/60/etc)
> appear to be differential analog.  I'd welcome more information from
> someone in the know.

I haven't seen anyone in the computer industry use an analog signal like
that in decades!

It begs the question of how they do it too!  Is there a wheatstone
bridge, or some form of network RC circuit, on the CPU module that the
power supply uses to compute the desired voltage with?

> > I think that's infinitely smarter than putting the VRMs right on the
> > motherboard like PCs do (or as some older M-bus modules did too).
> 
> Actually it was mainly the newer Mbus modules (which had lower and more
> critical core voltages) that required this.

Yeah, sorry, I meant "more recent Mbus modules" -- "older" meant "older
than the UltraSPARC modules"!  ;-)
 
> Depends on how you implement the motherboard.  Sun has tried it several
> ways.  The 5/10/AXi integrate voltage regulation with the motherboard, the
> 450 uses modular VRM's (like many PC's) and the 1/2/30/60 regulate the
> core voltage in the p/s.  The 450 VRM's look similar enough to some PC
> units to make me wonder if they're interchangable.

interesting....

I've also been trying to get more technical info on some PC VRMs.  I and
my clients have a bunch of IBM PC Server 325's with dual-PII CPU boards
in them, but so far only one CPU and one VRM.  With the coming of SMP in
NetBSD/i386 I want to be able to upgrade them, but getting the official
IBM VRMs is almost impossible and they are very expensive (over $50usa
each!).  They look very much like standard modules though, and I could
probably even build them from new parts for less $$$!

-- 
							Greg A. Woods

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