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Challenger Computer, inc, XT-186

eswan

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Saw a couple of threads on '186 based systems and thought I'd share this.
10 Mhz 80186, 640k. It's been many years since I fired it up, but I remember it acting as a typical 'turbo' XT clone. Pretty sure I never tried any 16-bit cards in the lower two isa slots, wouldn't count on them being actually 16-bit isa compatible.


cci-xt-186.jpg
cci-xt-186-cpu.jpg
 

eswan

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The lid is on in the first pic. Checking it over for date codes, it looks like it was made in early 1986, two years after the IBM AT introduction.So those bottom two slots most likely would have been made to take an isa standard 16-bit card, but how useful could that have been with only one interrupt controller and one dma controller?
 

Anonymous Coward

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I'm really curious about this board because of those 16-bit slots. Obviously they couldn't be fully AT compatible since the 80186 can't address above 1MB or do 16-bit DMA, but maybe the designer of this board tried to make slots that were partially compatible. It might be worth checking with a multimeter to see where things go. If everything lines up, it might be worth trying a few 16-bit cards in there to see what happens. It would be pretty neat for example if certain memory cards and VGA cards could benefit from the extra bandwidth of those slots.
 

Scali

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I'm really curious about this board because of those 16-bit slots. Obviously they couldn't be fully AT compatible since the 80186 can't address above 1MB or do 16-bit DMA

Well, most 286 systems only ever ran in real mode, and had 1 MB or less of memory, so I don't see how that would be much of a limitation for the 186 system.
I suppose you could add two 8259 DMA controllers on the board if you wanted 16-bit DMA functionality that is fully AT-compatible.
Sadly the pictures aren't clear enough to see just what peripheral chips there are on the board aside from the 186 itself, but there apparently are several large DIPs there.
Even so, 16-bit DMA was rarely used. Mainly by 16-bit sound cards, but those would have arrived years later. Besides, most of them are also backward-compatible with 8088-systems and can work with 8-bit DMA only.
 

Scali

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There were also some HDCs (SCSI and perhaps ESDI) that used 16-bit DMA.

There were? As far as I know, HDCs didn't use the onboard DMA because performance was far worse than CPU polling (the DMA controllers only ran at 3 or 4 MHz depending on the CPU speed).
I do know that some high-end HDCs had their own (fast) DMA controller on the ISA card. But that should work fine on any motherboard, regardless of the type of DMA they have onboard.
 

Chuck(G)

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There were. I'm not certain if it was legacy 8237-type DMA or bus-mastering, however. I think I even have a QIC tape controller that uses 16-bit 8237 DMA.
 

trr94001

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Interesting. I was under the impression that a ‘186/‘188 system couldn’t be 100% IBM compatible because the integrated IO weren’t the same parts that IBM used. Does that thing run big standard DOS or is it custom?
 

Jmdlcar

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I think when I had trs-80 color3 computer I own a 80186 computer I bought it from Radio Shack it was used but it was short lived for me. I know my brother had an 8088 at the same time. That about all I can say about it.
 

2icebitn

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I think when I had trs-80 color3 computer I own a 80186 computer I bought it from Radio Shack it was used but it was short lived for me. I know my brother had an 8088 at the same time. That about all I can say about it.

Having an 8088 doesn't equate to pc compatibility. Having an 80188/80186 doesn't prevent. A designer can opt to ignore the onboard peripherals and build a vanilla style mobo with associated support chips. This may nor may not be the system board sold by a company in California that was touted as fully compatible. It' mobo was made in the US.

I pm'ed the op asking for detailed photos and firmware dumps. He hasn't replied yet
 

eswan

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I'll try to get the roms dumped and pics tonight.

The date codes on the chips point to it being made in early '86, two years after the IBM AT. Only has 1 interrupt controller and 1 dma controller. A quick look over the traces for the 16-bit slot makes me think they might be "compatible" for certain values of compatible. It looks like the dma channels on the 16-bit isa extension go to jumpers that let you map them to the lower dma channels. I'll have to fire it up with a 16-bit video card and see what I get.
 

eswan

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The size limits puts a strain on resolution. At least this one is in focus-
Main chips are Intel 8255A-5, 8253-5, 8237A-5. Keyboard, Timer, and DMA Controller?
The chip above the 16-bit slots is the typical 8259A interrupt controller.
Two banks of MN4164P-15A and two banks of HM50256P-15 ram.
8-bit config switch near the cpu, JP6/7 below the DMA controller, JP2,3,4,5 to the right of DMA controller.
JP8,9 near center of board, JP10,11 above the end of the upper 16-bit slot. JP1 by the (20mhz) crystal.
Silkscreen 'U3601 XT-186 MADE IN TAIWAN R.O.C.' between slots 3&4.
Any other close-up pics wanted?

quadrant2.jpg
 

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