Re: multiple motherboards

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Date: 8 Sep 2003 02:30:57 -0700

ray <pdqxyz@zianet.com> wrote in message news:<3f5bddbe$1@news.zianet.com>...
> Suppose I wanted to construct a computer with multiple motherboards as
> opposed to multiple processors on one board. I'm specificaly thinking of
> several mini-itx boards in one machine. What would be involved and where
> would I start?

I'e built such a device. Each motherboard has 256M of ram, and there
is a staack of them held up by M4 threaded pillars. I put an
aluminium plate the same size on the top and added a hard disk and a
network hub with the plastic case discarded. All of them are joined
to the network hub using the on-board RJ45 port, and I have a £5
network card in the top one to connect to the outside world.

I bought some of the PSU plugs from www.farnell.co.uk and made a
custom wiring loom to run all of them off one 350W PSU. There is a
small diode (1N4148) in seies with each PSU on line, so that if any
one motherboard tries to turn on the PSU it works and powers all the
others up as well. When you shut them down the PSU stays on until the
last motherboard is powered down. The PSU also powers the network
hub.

The top one boots normally, and then the others boot by NFS using the
PXE boot built into the bios. They all boot the same tftp image, but
with different swap files as set up by thier device name which they
get by DHCP from the master.

At the moment I have toggle switches on the reset lines, so that I can
get the top one booted before I release the others, but am working on
a simple buffer board to control the reset lines on the slaves from
the printer port on the master.

Next trick would be to put a KVM switch in the box too, but havn't
bothered with that yet.

The box is a cylendrical stainless wastebin with a black pop-up lid.
I've put some rubber feet under it so that there is a space underneath
for the cables to come out and the air to get in, and slotted the edge
of the lid for the air to get out. The only fan is the one in the
PSU, which is very quiet. I mounted the whole PSU on rubber washers
(tap washers actually).

I have to lift the lid to get at the toggle switch array, and may yet
make a false panel inside with loads of LEDs on it. But I havn't
bothered yet.

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