Pentium Pro mainboard not working, please help!

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PetroffHeroj

Hello, folks.

Recently got a Pentium Pro mainboard; processor included, 4 72-pin SIMM
slots, built-in audio (some Crystal) and MIO, and so on -- yer olde server
brand from the middle of the 90's. The power supply wasn't included, neither
was the case or any peripherals, except for the bus multiplexor: the board
has only one EISA-lookalike slot, where you stick the multiplexor to get 3
PCI and 2 ISA slots.

After hooking the board to a usual AT power supply and sticking in a video
card and some SIMMs, I turned that mess on, but nothing worked for me. One
of the video cards kept giving some skewed retrace and garbage (anyway, it
looked like dirty white diagonal stripes running down the screen), and
others were just black. The keyboard didn't get init'd (stayed with LEDs
on), the speaker was silent even after I took away all memory modules and
later the video to see if BIOS complains -- the board was silent.

Now, the funny thing is that, although having an AT power connector (vs
ATX), it also features an extra one labelled "STD 3.3V". That one looks
exactly like one of the two AT connectors and neighbours them closely. I was
told it was, ahem, "optional". But the board originally used it (of course).
But that power supply with an extra dangle is long gone.

Could it be that the board is not dead, and I just have to get a power
supply from a more or less similar brand to make it work? In that case,
would any such power supply do or not?

There are also a couple of connectors that might be crucial to the board's
operation. One of them is in the line with the usual pins for speaker, LEDs
and stuff, and is named "SW_ON/SLP" ("switch on/sleep", I guess), and has
four pins. The other is 3-pin and looks exactly like a an-board fan
connector; that one is labelled "S-OFF". May be I've got to short-circuit or
pulse some of the pins on those to get the board alive?

Any comments will be really appreciated. Pentium Pros were rare beasts even
back then when people actually heard of them once in a while (1995-1997),
and these days laying my hands on that board was a real miracle. Suffice it
to say that it's the first Pentium Pro CPU I saw face to face :) The guy
must have pumped iron a lot judging by its size ;) Anyway, it's no wonder I
desperately want to see that thing working.

So far all I got is that the CPU _heats_ somewhat after several minutes of
(non-)operation. So may be the board is not dead after all?

Thanks!

Leonid
 
that board may require EDO or FPM memory ... also might require 50ns or 60ns
refresh on the DRAM.
Yes, typically the PPro boards with the extra power header needed the extra
power, although most of the old PPro boards were 5v on the mains.

Did you try clearing the CMOS and giving it another go?

What information do you have about the board ... are there any markings
silkscreened on the board itself?

- NuTs
 
After hooking the board to a usual AT power supply and sticking in a video
card and some SIMMs, I turned that mess on, but nothing worked for me. One
of the video cards kept giving some skewed retrace and garbage (anyway, it
looked like dirty white diagonal stripes running down the screen), and
others were just black. The keyboard didn't get init'd (stayed with LEDs
on), the speaker was silent even after I took away all memory modules and
later the video to see if BIOS complains -- the board was silent.
Click to expand...

This bit about the keyboard had me thinking "power supply problem" even
before you mentioned the additional power connector. The simple reason
being that the keyboard diagnostic isn't done by the computer but by the
keyboard itself upon power-on (it gets confused with the POST tests
simply because the computer is running these at the same time). If your
keyboard lights are staying on it means that the keyboard isn't happy
for some reason - if it works elsewhere it's almost certain to be its
power supply that is causing this.
 
Thank you, fellows, for responding with your helpful suggestions!

I had trouble getting the answers though thanks to my ISP's news server
quirkiness. It choked and disposed a good handful of articles into nowhere,
and I only learnt about and got your replies recently from
groups.google.com.

Thanks again. I'll be sure to follow your advice and make an attempt to do
something about the PSU. It's a lot better to have a PSU problem, however
bad, than having a dead mainboard... of possibly jewelry value :)

To Andrew:
AS> This bit about the keyboard had me thinking "power supply problem" even
AS> before you mentioned the additional power connector. The simple reason
AS> being that the keyboard diagnostic isn't done by the computer but by the
AS> keyboard itself upon power-on (it gets confused with the POST tests
AS> simply because the computer is running these at the same time). If your
AS> keyboard lights are staying on it means that the keyboard isn't happy
AS> for some reason - if it works elsewhere it's almost certain to be its
AS> power supply that is causing this.

I didn't realise that, thanks! I erroneously believed the keyboard doesn't
get init'd by itself on power-on, and it's only the BIOS that sends the
internal diagnostics command to it; until that, I believed, the keyboard
stays with LEDs on. This was plain wrong, as I proved myself by
disconnecting and reconnecting the keyboard and watching it passing the
diagnostics, blinking the LEDs momentarily, and finally sending 0AA.

A good guy on EFNet said it's very, very likely that this board _requires_
the additional wires on the third power connector in order to function
properly, and that's why it doesn't want to get alive. Quite correlates with
what you are suggesting.

Leonid
 
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