Different types of Intel Inboard 386/pc's

[Cimonvg]

hello
For some time my notion were - there are two different versions of the Inboard386/pc.
But is it so ?
The inboard with 8 bit RAM chips (non parity type)
..i have a DOA card with inner sticker:
fcc id EJM5MYINBRD386PC (Singapore)


(i have tried a quick repair - but my card is still not working)

and the Inboard with the 9 bit RAM chips (with parity).


i have working cards, with inner sticker:
fcc id: EJM5R7INBRD386PC (made in USA)
fcc id EJM5R7INBRDAT386 (no - "made in..")
..i have not seen any difference in performance the two card compared.

But looking at the introduction of the Inboard (1987) it seems there is another version
here:
https://books.google.dk/books?id=gC...AFegQIBxAB#v=onepage&q=inboard 386/pc&f=false

- with the coprocessor placed above the 80386 socket.
At first i was septical wether the oldest type only were some Beta version and not up for sale. But some days ago i spotted the older version again in other commercials. So perhaps there IS three types around?

And today i did search , and there is a RAM piggyback up for auction. (not me selling or buying)
https://www.ebay.com/itm/Genuine-Intel-Inboard-386-Piggyback-Memory-NOS-Sealed/174379178648

The box PCIB3120 only says "inboard386" not 386/pc or 386/at, if you search for the model: "PCIB3120" it is made for the inboard386/AT
and i am speculating - do the oldest type of inboard 386/pc have connections to external RAM card, exactly the same ase 386/at ?? - try and look at old commercial here:
https://twitter.com/foone/status/1237637634375036928

I have not seen and of the oldest on auction - have any of you seen the oldest Inboard386 type , in person ?

Again , i do only have Inboard with 8 and 9 chips RAM, so i am only speculating whether the oldest 386/pc and 386/at have the same RAM-expansion connectors.

/cimonvg

 

[cb88]

The advertisement literally says the IB1200 can accept a piggyback board IB1210 officially up to 2MB expansion for 3MB total. It's likely it would accept the 4MB card also and theoretically 8MB cards but I don't think nc_mike has made further progress at this yet.

 

[stynx]

Hi,

i have seen both the non-parity version (8 chips) and parity version (9 chips) in the wild. The non-parity version seems very rare and might be a later model than the parity version. Regarding memory: i suspect that the inboard 386PC has a total of 4 memory banks with up to 4mb per bank. The memory decoder logic would therefore be able to drive 16mb of memory. The inboard has one bank of 1mb that is not really upgradeable without massive modifications. Since each bank can have 1mb or 4mb of memory, a 12mb expansion may be possible for a total of 13mb memory.

-Jonas

 

[Cimonvg]

hello
cb88 - on picture from twitter , the inboard386/pc has like 3 connectors and then 1 connector (for RAM expansion). Like the picture below of the Inboard386/at.
the 8 chip and 9 chip versions have j1 and j2 each 40 pin.

stynx - i think the easy solution is upgrading the 2Mb ram card with 1mbit chips , in total 8 mbyte ram
or perhaps (just a thought) upgrade the 2mb module with one 1mb (soldered) and the free sockets filled with 1mbit chips - in total 5mb extra ram ?
..the 1mbit chips only lacks the A9 pin . But i have NO idear if it works :Oo .

question ..i believe there is only two WE signals to the expansion board - how would you access the third bank ?
/cimonvg

 

[stynx]

question ..i believe there is only two WE signals to the expansion board - how would you access the third bank ?
/cimonvg

You are may be right. But there is one signal line that is unaccounted for.