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Help identifying strange 286 motherboard

Hinoserm

Hinoserm

New Member
Joined
Dec 13, 2019
Messages
9
Hi,

I'm hoping someone can tell me more about this weird motherboard that I'm guessing was some kind of prototype. It has a 286 CPU but wants an XT keyboard. POST says "Copr. 1984,1985 SAMSUNG Personal Computer", and the ROM stickers are hand written. There's an engineering sample component installed in what I assume is the main chipset.

Markings on the board read:

MICRO MAIN COMPUTER CORP.
3921 WILSHIRE BLVD. SUITE 303
LOS ANGELES, CA 90010
PH (213) 387-9344
TIGER-286 MOTHER BOARD

I haven't been able to find any information at all about this company or what system this might have originally been for, nor do I have any info about where it originally came from.

Attached includes a copy of the ROM. More photos: http://otis.io/misc/tiger286/



tiger286-overview1-small.jpg
 

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  • tiger286-engsample-small.jpg
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  • tiger286-markings-small.jpg
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  • tiger286-rom.zip
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It looks like this could possibly be an early version of an "upgrade" motherboard that was meant to replace the MB in an XT system See the advert on page 113 here. Hence the XT keyboard. There is also an early BIOS database referenced here that includes a Tiger MB, but it is an award BIOS not the Phoenix BIOS on your machine. In the brief search that I made, I could not turn up anything on the "Samsung" end, which would seem to be the more obvious identifier. Interesting stuff - hope you will let us know where the search takes you.
 
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Not so extrange ... there are several accelerators or XT replacement boards (Pepper XT, Breakthrough 286) that used a 286 processor as a fast 8086
 
I never did understand why XT286 motherboards were a thing
they weren’t that uncommon and Tandy made a business of having XT class motherboards with 286 processors

Kinda breaks the point of having a 286 board when you can’t break the 1mb barrier, have XT DMA & IRQs and are stuck with everything 8 bit.

Especially when you could buy normal 16bit 286 boards with multiple 8 bit slots for your antique cards. I used 8bit mfm, serial I/o and video cards in 286 systems without issue.


Looking at that link I have no idea where that 24mhz speed limitation came from on vintage motherboards when no cpu was made that speed
 
rmay635703 said:
Looking at that link I have no idea where that 24mhz speed limitation came from on vintage motherboards when no cpu was made that speed
Click to expand...
Predicting the future hard; it's easier to measure the signal integrity and extrapolate to faster CPUs. 25 MHz 286 chips eventually happened.
 
syzygy said:
It looks like this could possibly be an early version of an "upgrade" motherboard that was meant to replace the MB in an XT system See the advert on page 113 here. Hence the XT keyboard. There is also an early BIOS database referenced here that includes a Tiger MB, but it is an award BIOS not the Phoenix BIOS on your machine. In the brief search that I made, I could not turn up anything on the "Samsung" end, which would seem to be the more obvious identifier. Interesting stuff - hope you will let us know where the search takes you.
Click to expand...

Someone else did recently bring that ad to my attention -- I wonder if it's the same board. Maybe they hired a contractor to design it and this was one of the original test/prototype/reference boards? Maybe they just grabbed a random pre-existing BIOS ROM off something else and shoved it in for the proof-of-concept?

Aside from the Award BIOS the other specs seem to match up. It must not have been a very popular product for there to be no other information about it left around.
 
Hinoserm said:
Someone else did recently bring that ad to my attention -- I wonder if it's the same board. Maybe they hired a contractor to design it and this was one of the original test/prototype/reference boards? Maybe they just grabbed a random pre-existing BIOS ROM off something else and shoved it in for the proof-of-concept?

Aside from the Award BIOS the other specs seem to match up. It must not have been a very popular product for there to be no other information about it left around.
Click to expand...
Replacement MBs of this kind were a relatively inexpensive way to gain some speed. Their popularity, to whatever limited extent, was short-lived. I dimly remember them and thought they were something on the 'not too useful side'. I suppose if you had some dedicated tasks, the speed increase might have been a cheap fix, e.g., if you had people taken smoke breaks waiting for their code to compile, one might spend $200 to placate their whining.

Unless you know something about the history of the board you can speculate on all kinds of things - yes, someone certainly could have burned replacement BIOS chips.

What have you found out about "ENG SAMPLE" on the CPU? Who made that? Have you looked up that maker mark? It is natural to think that you have something unusual, a prototype, rare and valuable, and so on, but only a lot of background work will answer the questions.

Good luck and let us know what you find out.
 
iMP mark on the CPU appears to be a subsidiary of National, considering neither national or its overseas compatriots never made a 286 (that I’m aware of) must be a evolutionary dead end.

Sort of like the ns486 or N7 that only existed on paper
 
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rmay635703 said:
iMP mark on the CPU appears to be a subsidiary of National, considering neither national or its overseas compatriots never made a 286 (that I’m aware of) must be a evolutionary dead end.
Click to expand...
The CPU is the part under the heatsink and is just a regular Intel 80286 in CLCC package; the part marked IMP is presumably the main "chipset" of some sort. The part number hasn't lead me anywhere. No markings on the underside.

Where did you find the info that the IMP mark belonged to National? I haven't been able to find another example of the mark.
 
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I suspect the Eng Sample chip is more a "chipset" than CPU. The CPU might be U12 under the heatsink.
 
rmay635703 said:
I never did understand why XT286 motherboards were a thing

Kinda breaks the point of having a 286 board when you can’t break the 1mb barrier, have XT DMA & IRQs and are stuck with everything 8 bit.
Click to expand...

I guess there was a market because nobody could test and claim full 286 -> XT backwards compatibility with all the 8bit peripherals.
 
This is a different manufacturer, but a very similar 8-bit 286 board:

Wave Mate BULLET 286 018-011 REV A (XT-version)

Wave Mate BULLET 286 018-011 REV A (XT-version) is a motherboard based on the IBM AT chipset chipset. Get specs, BIOS, documentation and more!
theretroweb.com theretroweb.com

Please take the time to document and add this unique board to TheRetroWeb. It's an amazing site, and gets better every time we add a new device.

- Alex
 
rmay635703 said:
iMP mark on the CPU appears to be a subsidiary of National, considering neither national or its overseas compatriots never made a 286 (that I’m aware of) must be a evolutionary dead end.

Sort of like the ns486 or N7 that only existed on paper
Click to expand...
I don't know - are you sure? I know about the IMP from NS but this iMP appears to be IMP Inc which was merged / bought out / acquired by Daily Silver Holdings in 2004 and now operates as DS-IMP .

Here is an old datasheet for a completely unrelated chip but the logo is unmistakably the same as that engineering sample.

They currently have UART chips that even include a parallel port. Is it conceivable that such a version made it to the MB?
 
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