Challenge: Motherboard from 1994

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Challenge: Motherboard from 1994

Postby aideed » Thu Nov 17, 2011 10:14 am

I need help finding a manual for my severely outdated motherboard. I need to find out which power supply pins to short for the board to turn on. I can not turn off the second computer or risk reseting it using a DMM.

The BIOS code for the motherboard is 51-0802-006089-00111111-101094-NEPEISA-R (I have two of these motherboards, one works the other doesn't)

The only information I could find on it was http://stason.org/TULARC/pc/motherboards/C/CSS-LABORATORIES-INC-Pentium-MAXPRO-MAXSYS-PRORACK.html

Here is a photo
Image

Thanks for helping!

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Postby Hardware Junkie » Thu Nov 17, 2011 10:54 am

If you found your board in TH99 then that's probably the only info available.
This is an AT motherboard, not ATX. There are no pins and need to be shorted for this to power on. The power supply has a hard switch on it.
You'll need matched pairs for your memory, and hopefully no one has screwed with the other jumpers on the board (because most were not documented for users to mess with).

I don't know where to find a supplier for AT power supplies. There might be someone still making them.

Edit: probably ebay is your best bet. Search for "AT power supply"
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Postby evasive » Thu Nov 17, 2011 2:02 pm

Not listed in here but you can try emailing CSS:
http://www.csslabs.com/customer_support/manuals.html

the single pentium MMX in that list is the MB-5865, yours is MB-5863, so who knows, they may have more info. Thank you for posting the bios string, we didn't know 006089 AMI manufacturer code is CSS labs.
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Postby aideed » Thu Nov 17, 2011 3:05 pm

I have tried calling and emailing CSS but I have heard nothing back from them.

I think I read somewhere that they were going/are out of business.

Thanks for the ideas, no luck yet.

I think there is some strange logic on the power dist board. I haven't had time to recap the newer power supply to interface with this board yet though. Waiting on a Digikey order...

Image

Was hoping it was just a jumper config but oh well.

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Postby evasive » Thu Nov 17, 2011 10:20 pm

Can you post a picture from the working board for comparison so I can make an estimated guess if your handywork is going to do something in the first place? Looks like you've been bypassing quite a few things....
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Postby Karlsweldt » Fri Nov 18, 2011 8:14 am

Older motherboards from the mid-1990s normally did not have a 20-pin ATX connector.. only the 12-pin AT power header. And the PSU for those models is very rare, today.. plus it would have had a -5 volt source, missing on the ATX PSU design.
There once was an offer of a conversion adapter, to use an ATX PSU on an AT setup.. but found no listings except at eBay.
Most of the older AT mobo designs did not have need for the +3.3 volt source.. creating it from the +5 volt source, if needed, with the Pentium II MMX series of CPU. But some mobo designs did have a separate 6-pin connector for an external +3.3 volt supply.
But check with www.eBay.com/ in Computers and Networking and you will find some older AT PSU offers. Go with at least a 200 watt unit, if running dual CPU setups. www.pinouts.ru will have an extensive listing of pinouts for almost every computer-related connection!
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Postby aideed » Fri Nov 18, 2011 9:06 am

Karlsweldt wrote:Older motherboards from the mid-1990s normally did not have a 20-pin ATX connector.. only the 12-pin AT power header. And the PSU for those models is very rare, today.. plus it would have had a -5 volt source, missing on the ATX PSU design.
There once was an offer of a conversion adapter, to use an ATX PSU on an AT setup.. but found no listings except at eBay.
Most of the older AT mobo designs did not have need for the +3.3 volt source.. creating it from the +5 volt source, if needed, with the Pentium II MMX series of CPU. But some mobo designs did have a separate 6-pin connector for an external +3.3 volt supply.
But check with www.eBay.com/ in Computers and Networking and you will find some older AT PSU offers. Go with at least a 200 watt unit, if running dual CPU setups. www.pinouts.ru will have an extensive listing of pinouts for almost every computer-related connection!


Thanks for all of the research. I actually do have a power supply with +/- 5v on it and the board to regulate 5v down to 3.3v for the cpu.

I am going to take some pictures of my working PC and post them soon.

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Postby aideed » Fri Nov 18, 2011 10:29 am

Here are two pictures of the working motherboard.

One shows the power dist board and the other shows the relay. I think that the relay is stopping me from powering on fully.

The third picture shows both pieces.

http://imageshack.us/g/717/img20111118090828.jpg/

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Postby Karlsweldt » Sat Nov 19, 2011 6:32 am

In viewing those images, looks like the original setup had two power supplies, or one massive one of more than 400 watts. Likely this was a network server, with multiple terminal connections and several storage drives. You may not be obtaining the full power source that is default to the system, to get any signs of life. If using only one CPU, it would have to be in a specific socket.. and some jumper or switch settings made to enable the "single" mode. Then too, some of those older designs used a cache memory module, similar to the early SIMMS.. but with a very fast memory speed.. and a dedicated slot.
Would be nice to have a POST diagnostics card at this time, to note what processes are hanging the pre-boot regimen. Some BIOS types would only boot to a network "head end", while others could be BIOS set to self-boot to internal OS sources. If there are SCSI data headers, the BIOS may be seeking an OS or boot path via that feature.. and ignoring any IDE features. Hopefully, the BIOS does not need a special access disk to change settings. That could make the pleasure of seeing this mobo come to life a distant reality!
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AT powersupplies

Postby sirrushx » Tue Nov 22, 2011 12:43 pm

Hardware Junkie wrote:If you found your board in TH99 then that's probably the only info available.
This is an AT motherboard, not ATX. There are no pins and need to be shorted for this to power on. The power supply has a hard switch on it.
You'll need matched pairs for your memory, and hopefully no one has screwed with the other jumpers on the board (because most were not documented for users to mess with).

I don't know where to find a supplier for AT power supplies. There might be someone still making them.

Edit: probably ebay is your best bet. Search for "AT power supply"
8


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