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Challenge : Old 286 motherboard
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fussnfeathers
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PostPosted: Mon Aug 23, 2010 11:15 pm    Post subject: Reply with quote

evasive wrote:
Hardware Junkie wrote:


Additionally, I am not seeing a BIOS chip on the board. I think that empty socket near the keyboard is where that is supposed to be.


no that is for the 80287 co-processor. for those of you never seeing SIPP memory module sockets: you're right, the pins on the memory sticks kept breaking of, that is why they quickly went to the memory slots you may know from the pentium boards. those of you with a few more years, either in age or in experience would recognize these babies directly though. I may even own a board with them.


Ye Gods, how many of those did I install with no instructions?
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jeremfg
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PostPosted: Tue Aug 24, 2010 9:34 am    Post subject: Reply with quote

Karlsweldt wrote:
Finally found the link to this site which lists many older mobo designs. But found nothing close.


I visited this website before posting, and didn't find anything either.

Hardware Junkie wrote:
Just went through the 286 boards in TH99 and didn't find any matches...


Thanks for bringing that up... It's been a long time since I last visited this website (5+ years) and had forgot about it.

And I did find my motherboard on TH99! It's there! But it doesn't help much though! It's marked as "unidentified"

Here's the link!
On their schema. there's a number : MH2214. But I have no idea what it means!
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evasive
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PostPosted: Tue Aug 24, 2010 10:51 am    Post subject: Reply with quote

So Vtech as manufacturer, 286/16 ISA as type number is not going to be good enough? Because that is as good as it will get most likely. provided you can get it to boot and reply with the bios identification string that might hold the model number. But i would not count on that.

You did do a proper job on picking it out of the long list of motherboards.
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PostPosted: Tue Aug 24, 2010 12:39 pm    Post subject: Reply with quote

jeremfg wrote:

And I did find my motherboard on TH99! It's there! But it doesn't help much though! It's marked as "unidentified"

Here's the link!
On their schema. there's a number : MH2214. But I have no idea what it means!


If that's the board, that's as much info as your going to find I think.
Time to boot the sucker and hope for the best.
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PostPosted: Tue Aug 24, 2010 1:14 pm    Post subject: Reply with quote

evasive wrote:
So Vtech as manufacturer, 286/16 ISA as type number is not going to be good enough? Because that is as good as it will get most likely. provided you can get it to boot and reply with the bios identification string that might hold the model number. But i would not count on that.

It's very good! But I'm kinda of always wanting more big grin. It's never enough I'm like that!

With everything all of you have said, I've became conviced that this motherboard was pulled from a Vtech Laser 286
I'm in the process of trying to confirm that with them.
They have at least the user manual (if not the computer that goes with it), so they might be able to confirm my belief!
If it can be confirmed, I might also be available to get a scan of this manual!

As for booting it up, I might do that when I get to it (it's not stored in my home right now).

I'll get back when I know more!
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Karlsweldt
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PostPosted: Tue Aug 24, 2010 2:12 pm    Post subject: Reply with quote

If indeed that user manual is for the 286 mobo, then you can decipher the jumper settings and that 4-gang DIP switch. Back then, the parallel port did not have a 'default' setting of 378h.. more like 3BC, following the original IBM scheme. There also should be one jumper for setting the video mode, either monochrome or color. There also may be a lockout feature on the BIOS.
As to memory, you definitely will need those SIPP modules. Two may work, but may be best to try with four identical modules. 80ns or 70ns should work well on that board.
There should be two connection pins at the edge, marked "turbo" that allows switching from high speed (16 Mhz) to low speed (8~12 Mhz) so as to accommodate older programming that ran on system clock timing, rather than real-time clock.
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PostPosted: Tue Aug 24, 2010 5:10 pm    Post subject: Reply with quote

Hardware Junkie wrote:

http://www.google.ca/search?q=GM71C4256A-80


Amazing that you can still get spares for boards of that age. eek

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PostPosted: Tue Aug 24, 2010 5:19 pm    Post subject: Reply with quote

Karlsweldt wrote:
If indeed that user manual is for the 286 mobo, then you can decipher the jumper settings and that 4-gang DIP switch. Back then, the parallel port did not have a 'default' setting of 378h.. more like 3BC, following the original IBM scheme. There also should be one jumper for setting the video mode, either monochrome or color. There also may be a lockout feature on the BIOS.
As to memory, you definitely will need those SIPP modules. Two may work, but may be best to try with four identical modules. 80ns or 70ns should work well on that board.
There should be two connection pins at the edge, marked "turbo" that allows switching from high speed (16 Mhz) to low speed (8~12 Mhz) so as to accommodate older programming that ran on system clock timing, rather than real-time clock.



Thanks! I already knew all that...

As for deciphering jumpers, I can already do that with the information found on TH99, which I posted earlier!

By the way, there isn't a parallel port on this board. However, if I'm correct in saying that this board was pulled from a Vtech Laser 286 computer, that computer had it's own 8-bit ISA I/O Card which provided parallel and serial port. And apparently, this card can still be found (bought) on the web!

Also, I don't really need SIPP memory to test the board, I could get up to 1Mb of RAM using only DIP memory (According to what I found on TH99). But if I would go as far as use it, I would definitely get 2 full banks of SIPP modules (4x1Mb) to get the maximum out of it, 4Mb.
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evasive
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PostPosted: Wed Aug 25, 2010 3:59 am    Post subject: Reply with quote

yep, not all of the DIP sockets were for cache memory.

However, if you are going to use the 4MB sipp's, you may want to fit some cache memory chips as well, might make this system useable. Most likely those need to be 10ns or 12ns chips.

Any 8bit or 16bit ISA multi I/O card should work, you may even be able to fit an IDE controller card.
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jeremfg
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PostPosted: Fri Aug 27, 2010 9:30 am    Post subject: Reply with quote

I'm still unclear about that...

Where would the cache memory go?

When I read the info on TH99, all the sockets are for DIP DRAM!, and the empty one for a math co-processor!

Unless it has something to do with the parity chips, or something I don't get!

I guess it has something to do with the 2 choices of DIP which interleave themselves across "Bank 1B" (as shown on TH99).

Could you please explain this interleaving giving two choices? Thanks!
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