Beowulf in a Box

[Kragen]

On Mon, 28 Sep 1998, Bob Drzyzgula wrote:
> On Sun, Sep 27, 1998 at 08:15:59PM -0400, Kragen wrote:
> > Well, broadcasting and multicasting are, I think, possible over
> > Ethernet, but not over PCI.  Also, AFAIK, the PCI switches you speak of
> > are vaporware at the moment, while Fast Ethernet switches are not.
> 
> So, here I'm confused. This board that is being discussed
> is using PCI as an interconnect, right? And the I2O
> protocols are being used as the basis for a TCP/IP
> implementation? Now, I know very little about I2O -- is
> I2O only point-to-point? How would a broadcast work
> on one of these eight-SA110 boards if PCI doesn't
> allow for broadcast?

I know nothing.  I assume a broadcast would work by first sending to
the first CPU, then the second, then the third . . .

> Both PCI switches and this board are currently vapor,
> although it seems that an attempt to assemble these
> SA-110 boards may be soon 

Yes, I think it should be next month that the first CPU cards are
built, and the month after that that the main PCI boards go into
production.

> and I haven't identified anyone
> attempting to build a PCI switch, only a ring. Still,
> there could easily be several iterations before all the
> timing and software issues are worked out to the point that
> the SA-110 boards can be stamped out and sold in volume;

This is conceivable; I don't know much about the issues involved here.

> few new circuits of this complexity 

I think they are rather simple, actually; the CPU cards will have a
CPU, some memory chips, and a PCI bridge circuit on them, and (I'm told
thirdhand) that's it; the main PCI card will be even simpler.

The really hard work has already been done by engineers at DEC.  :)

> are fully functional
> on the first try, I would suspect. Until that time, it
> seems to me that in this thread we are discussing what
> might be and not what is. Or have I missed something?

You are correct.  The SA-110 boards are relatively solid vapor, though
-- two or three months, I think.  They're just a simple matter of
engineering well-understood stuff.  I don't know about PCI switches and
stuff; that sounds more like a simple matter of black magic.

The SODIMM-slotted Fast Ethernet adapters are also total vapor, though;
nobody's started trying to design them, although I can't imagine it'd
be hard -- they're just PCI Fast Ethernet cards with a funny form
factor.

Kragen

-- 
<kragen@pobox.com>       Kragen Sitaker     <http://www.pobox.com/~kragen/>
The sages do not believe that making no mistakes is a blessing. They believe, 
rather, that the great virtue of man lies in his ability to correct his 
mistakes and continually make a new man of himself.  -- Wang Yang-Ming