Challenge : Old 286 motherboard

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Postby jronald » Sun Aug 22, 2010 11:42 am

Im sure I have the ISA cards you need. May have the memory but I doubt it. Should have the HDD also. Yours for shipping, let me know.

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Postby Karlsweldt » Sun Aug 22, 2010 11:55 am

As to any stains or corrosion from the battery, use common vinegar on a cotton swab to neutralize the acidic compounds. Then use baking powder in water (1:50 or so ratio) to neutralize the vinegar and then use moist cotton swabs to clean the area. Likely the protective coating has been eaten away by the acids, and possibly some copper traces have been eaten also. But if the traces are still intact, the board should work. If you cannot find a replacement battery, then possibly the plastic clip for the now-standard coin cell will fit those solder holes. Should be a mark on the surface for the (+) terminal. Have done so with several older boards. But if there is a 4-pin header nearby, that could be used for an off-board BIOS battery of 3 volts. Generally, pins #1 and #4 are the battery connections. To repair the protective coating, clear nail polish will work nicely.
Most of the early 286 mobo models did have 1 meg of on-board memory. Sufficient for the early DOS or other OS types. DOS 5.0 would be an ideal candidate for a boot disk. The 286 mobo types can accept a 1.44 MB disk drive. But the hard drive would be a problem, unless you can find one having no more than 1024 cylinders, 4 heads and 17 sectors per track. Only the latest 286 models had a broader range of hard drive choices.
As evasive noted, there are no on-board connections for the floppy or hard disk. That task goes to an ISA multi I/O card, having the serial/parallel ports as well as FDD/HDD ports. The video card of course would be an ISA type. 256 megs or less of video card memory will suffice. There are still some offers on eBay for those cards. Same for older sound cards.
But without a video card and I/O card, the system will not respond.
You need a power supply with two power plugs having 6 leads each. Ensure that the black leads are together in the center!
Still looking for those old manuals..........
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Postby Hardware Junkie » Sun Aug 22, 2010 1:48 pm

Pette Broad wrote:Hmm, I don't see any IDE connections, so either it pre dates IDE or is some kind of terminal that ran through a token ring ISA card. Not at all familiar with 286 boards, but I'd say 1990 or earlier.

Pete


Back then we had to use controller card to hook up a hard drive. It pre-dated ATA technology and usually used MFM (Modified Frequency Modulation) instead of something like FAT.

Best bet for a hard drive on this board would be to find a Promise EIDE Controller card that can use IDE drives.

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.
BIOS companies used to have huge stickers on the chips indicating the developer. And they were also removable.
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Postby Pette Broad » Mon Aug 23, 2010 11:08 am

jeremfg wrote:Do you believe that the currently installed memory as gone bad?


If you mean the Goldstar chips near to the memory sockets, then I'm pretty certain they are cache memory. It's been a long time since I dealt with cache memory but I think one of chips, known as TAG Ram needs to be 60ns and I only see 80ns chips in there. I could probably supply a 60ns chip off one of my old boards if required, they were fairly common right up to the 486. Not sure about the memory itself though, I've never seen main memory that goes into holes like that and I've been dealing with PC's since 1990.

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Postby Hardware Junkie » Mon Aug 23, 2010 2:04 pm

Pette Broad wrote:
jeremfg wrote:Do you believe that the currently installed memory as gone bad?


If you mean the Goldstar chips near to the memory sockets, then I'm pretty certain they are cache memory. It's been a long time since I dealt with cache memory but I think one of chips, known as TAG Ram needs to be 60ns and I only see 80ns chips in there. I could probably supply a 60ns chip off one of my old boards if required, they were fairly common right up to the 486. Not sure about the memory itself though, I've never seen main memory that goes into holes like that and I've been dealing with PC's since 1990.

Pete


The Godstar chips are FPM DRAM. Your right about the 80ns though.

Google Search on the chips:
http://www.google.ca/search?q=GM71C4256A-80
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Postby Karlsweldt » Mon Aug 23, 2010 2:39 pm

Finally found the link to this site which lists many older mobo designs. But found nothing close. Indeed those Goldstar chips are only cache.. 256 K worth, noted by the center line of characters. If there were on-board memory for the system, then you would need two banks of nine DIPP chips each to equal either 512 K or 1 M. The 286 mobo designs used the SIMM type memory modules toward their end of production. The earliest models used on-board memory with DIPP sockets. There were add-on memory cards which were quite popular for those older mobos. Some, like AST and Compaq, used dedicated memory cards.. no slots on-board, save for the CPU cache.
Just below the processor are two large DIPP chips.. those are for the BIOS. There are still some offers on eBay for those SIPP modules!
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Postby evasive » Mon Aug 23, 2010 3:53 pm

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.

As to the original question, what is it: a 80x86 motherboard made by the Vtech company, either for one of their Laser Computer machines or maybe used in a Tandex or Elonex system. problem here: 80286 is still very much printed paper manual era, chances on a scanned copy of that are slim. I'll go through some boxes... That socket looks a lot like 80386 already though, maybe that 80286 was a low-power variant or something... I'll do some more digging...
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Postby Hardware Junkie » Mon Aug 23, 2010 6:33 pm

The processor is an AMD knock off, still a 286 in every respect though.

http://www.cpu-collection.de/?l0=co&l1=AMD&l2=80286

Remember when AMD just re-created Intel's designs? This 286 was from the days before they started creating Amx86 designs that had differences from Intel counter parts.

Edit: The chip marked HD146818P - looks like thats the CMOS chip. Odd, it looks like its permanently mounted. Used to seeing them removable back then.
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Postby Hardware Junkie » Mon Aug 23, 2010 7:51 pm

Just went through the 286 boards in TH99 and didn't find any matches...
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Postby evasive » Mon Aug 23, 2010 10:20 pm

I checked the site of the Japanese collectors and nothing there either.

A27C001 but not helping any further yet.
ACT = Advanced Computer Technology LTD, Hongkong
they made chipsets in the past but were only famous for the 386dx40 and early 486 chipsets.
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