[RC5] Rack stuffed full of motherboards (follow-up)

NP np at cableinet.co.uk
Thu Apr 30 01:33:19 EDT 1998

Many thanks to all who responded. (I had quite a few replies not sent to
the list too).

I must say I was suprised that ALL were very positive, not one "Don't be
stupid" !
What an enthusiastic bunch you are.  I appreciate all your

Here's the aim so far:

6 foot rack.
m/b's with IBM/Cyrix M2 200MMX chips + heatsink + fan + 8 MB RAM +
network card with boot ROM.
Mounted vertically (for better air flow) in groups of 5.
1 x 4" fan (more if need be) top and bottom to get a decent throughput
of air.
(The ambient temperature at the intended location is usually fairly cool
If the "1 PSU to many m/b" approach works, each PSU will power
alternately placed m/b's - allowing for 1/2 the boards to be powered
down if temp does rise too high).
No hard drives, no floppies.  (Less juice, no floppy shuffles, more
Slimline (cram more in) cheapo network cards with boot ROMs. (We've
successfully experimented with this over the last few days and have
Linux booting hard-diskless over a network.  Although we need to lay
hands on an EPROM programer to blow the boot image onto the network card
No video cards (some m/b's+BIOS DO boot without them I'm reliably
The whole thing will be networked off a home desktop PC for monitoring.
(I feel the need for a smoke alarm too !).

What next ?

We're off to purchase a load of P8/P9 m/b power connectors, 2 large
PSU's out of some old 386 servers, and hopefully pick up a rack on

I have conflicting information of what size current goes down the +ve
and -ve PSU rails,  so, we're going to find out for ourselves:
Chop into the cables of an old 200W PSU and measure the current drawn on
each rail by 1 m/b with the above configuration, to estimate how many
m/b's a given PSU might run.

Plug this PSU into 2 old m/b's (in parallel) and see if they boot or
If they depart up the chimney, we'll have to go for many small
individual PSUs.

Convince a few friends to try to boot their machines without video cards
and send us the results (to influence our chosen purchase of m/b+BIOS).

And last but not least, we concluded that it MUST be covered with
flashing LEDs and perhaps an LCD block counter hanging off a parallel
port  :-)

Progress won't be too rapid as there are just 2 of us doing this and we
are also busy with other things, but we are determined to progress this.

I'll post any more follow-ups to hardware at llamas.net (thanks for
pointing that out dB) and I'll put some pictures on my web site when we
have something built.

Regards, - Nick.

PS.  And one snippet I can't resist passing on; I received a reply from
someone (who I won't identify without his permission) who is planning a
similar build, but in order to avoid aquiring a rack, is planning to
suspend the beast from a ceiling with fishing twine.  I'm not mocking
him, that is a "remarkable" idea.  I can't wait to see a picture of that

Nick Pearce
Mobile/SMS. +44(0)370 450 542

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