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Seeking memory card for InBoard/386

N

nc_mike

Experienced Member
Joined
Sep 28, 2014
Messages
473
OK, ultra long shot that someone might have or know of an available 2MB or 4MB expansion piggyback/expansion board for an Intel Inboard/386...

I know, the lottery might have better odds, but it never hurts to ask!

Regard,
Mike
 
I've got the 1M base InBoard/386 PC board installed and working. I just missed out on a 2MB piggyback expansion board for the Inboard last month on eBay - Aeeeeeiii!!

:)

Thanks,
Mike
 
Im working on a pinout and schematic for a 2mb board and possibly even a 8mb board if i can get 4mb to work.
Its not really that complicated, just a lot of work ;-)

My last wire wrap prototype got to 1mb before i accidentally ripped some wires away.
It was too much work to repair this and i will make a pcb with 8mb dram and a small proto-area.

The 4bits of checksum are a pain and i will try to get around this with either a inboard-mod or a simulated crc check.

But don't expect anything this year...

-Jonas
 
stynx said:
Im working on a pinout and schematic for a 2mb board and possibly even a 8mb board if i can get 4mb to work.
Its not really that complicated, just a lot of work ;-)

My last wire wrap prototype got to 1mb before i accidentally ripped some wires away.
It was too much work to repair this and i will make a pcb with 8mb dram and a small proto-area.

The 4bits of checksum are a pain and i will try to get around this with either a inboard-mod or a simulated crc check.

But don't expect anything this year...

-Jonas
Click to expand...

An 8M add would be awesome! Would love to see that working.

Regards,
Mike
 
Robin4 said:
Nice to hear you have got some good result over there..
Click to expand...
define 'good results' ;-)

I have acquired a logic probe that will help me to debug the expansion connector. But the probe does not have a "clock in" ... that makes things a lot more problematic. The probe can monitor 16 channels at up to 16 mhz, 9 channels at up to 32mhz, 6 channels at up to 50mhz and 3 channels at up to 100mhz. BUT my inboard only allows me to use an oscillator of 22mhz or higher. That means 11.xx mhz effective cpu clock. I have problems to get accurate measures of the HIGH and LOW at 16mhz sample rate. I have tried a sample rate of 100mhz and encountered some irregularities with my previous measure that make my data more or less unusable. I need 12 channels with a sample rate of at least 60mhz to get usable results... right now my only chance is to get the cpu-clock to 8mhz that i can sample at 16mhz (should be more or less usable).

I don't want to spend another $500 for a 100Mhz 16 channel logic probe (right now).

Measures of the Signals while booting (inboard386 memtest)
Inboard386_XMS_memtest.jpg
Image on flickr

It would be nice if anyone who has some insight into memory timings and knows how to put the info into perspective would comment on this.

-Jonas
 
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Well, I got my hands on a 2M piggyback card but not by itself. The last one that appeared on eBay went for a whopping $400. So I spotted a complete Intel Inboard 386/PC for sale with a 2M piggyback daughter card for $78 which was bid up to $260 - still expensive but I plan to keep that one and sell my existing Inboard/386 PC without a daughter card as a complete package (cable, drivers, doc, packaging and a 386 math co-processor, tested and verified) on eBay to offset the cost. I am not sure what it should sell for - there is one for sale on eBay now for $250 not as complete as the one I plan to sell, but that's a pretty good price given earlier ones went for quite a bit more.

Regards,
Mike
 
Is there a good photo of this inboard and its memory expansion available somewhere? Maybe a memory controller could be identified which has a datasheet.
 
H-A-L-9000 said:
Is there a good photo of this inboard and its memory expansion available somewhere? Maybe a memory controller could be identified which has a datasheet.
Click to expand...

Go to eBay, search on Completed Listings and use Intel Inboard as the search string.

Mike
 
H-A-L-9000 said:
Is there a good photo of this inboard and its memory expansion available somewhere? Maybe a memory controller could be identified which has a datasheet.
Click to expand...

The Inboard utilizes PALs and TTL-logic to implement the memory controller.
 
I'd suggest you write a little program that does nothing more than switch to protected mode and continuously writes RAM addresses at the 1M/2M/4M locations.
I.e.:
- write byte at 0x0
- write byte at 0x1
- write byte at 0x2
- write byte at 0x3
- write byte at 1M+0x0
- write byte at 1M+0x1
- write byte at 1M+0x2
- write byte at 1M+0x3
- write byte at 2M+0x0
- write byte at 2M+0x1
- write byte at 2M+0x2
- write byte at 2M+0x3
- ...
- start over

Why writes? Because the memory is read all the time for code fetches, but you can filter these out by watching the /WE pin.
Then you can use your analyzer to check what all the signals do at these addresses, if accesses happen at all on all locations and how they differ.

If the memory controller is configurable by the BIOS the usefulness of this method is limited - but maybe that's not the case.
 
H-A-L-9000 said:
I'd suggest you write a little program that does nothing more than switch to protected mode and continuously writes RAM addresses at the ...
Then you can use your analyzer to check what all the signals do at these addresses, if accesses happen at all on all locations and how they differ.

If the memory controller is configurable by the BIOS the usefulness of this method is limited - but maybe that's not the case.
Click to expand...

I would if i could... i apparently fried my inboard somehow.
I suspect that i accidentally shorted a pin somewhere and destroyed a PAL.
Because of that, i am looking for a replacement inboard 386/PC and will pay a reasonable price.

The 2nd Inboard i have acquired seems to be defective as well...

Jonas
 
Wellll....I received the new Inboard 386/PC today and installed it. It replaces an InBoard 386/PC that had only 1MB of RAM on board. I THOUGHT the new card had a 2MB piggyback daughter card, I was mistaken. It actually came with a math co-processsor installed and the memory was not 2MB, it is a 4MB piggyback daughter card. I thought the 2MB daughter cards were rare....not sure but I think the 4MB daughter cards are ultra rare. I'm not complaining :D :D :D :D :D

Looks like I'll be selling the 1MB Inboard/386 PC soon! I am not sure what it should go for as the eBay prices have been swinging wildly on this one. The last one that was up there just sold and they sometimes don't materialize for up to 2 years - even the 1MB versions. The 1MB I plan to sell has everything, the original SW, cable, manual, accessories and box and has been fully tested. Anyone have a clue what it should sell for on eBay?

Regards,
Mike
 
Necroposting I know, however, we still don’t have a replacement for the InBoards 4MB daughterboard. Once we have a schematic for the original 4MB board, a new board with contemporary parts will likely have a significant lower chip count. I believe that a 16MB daughterboard is also a possibility.

Incidentally, an InBoard with the 4MB daughterboard sold for $1500 on eBay yesterday.
 
I watched that auction even though I wasn't bidding as I already have the 4MB daughter card. The bids on the pair were very low until the very end, then <pow!> wow! $1500. But those 4MB daughter cards rarely come up on eBay maybe once every few years, and the 4M even less so than the 2MB daughter card, so I guess that demonstrates the fundamental rule of supply and demand. Given the 4MB board is required to run Win 3.1 well with the InBoard 386 it is highly desirable. As was mentioned earlier and in other threads, the stock InBoard 386 rund at 16MHz and tops out at 33MHz with a 486 CPU upgrade unless the oscillator on the Inboard is also replaced. I simply replaced the 386 CPU with a CyrixCx486DRx2 20/40MHz CPU like this one: https://www.ebay.com/itm/Cyrix-Cx48...867646?hash=item48dc315bfe:g:VjoAAOSwl9xeE8di It's an easy drop-in replacement and makes the system fly, although that Cyrix only provides a 1MB cache - still happy with it.
 
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