Toshiba T1000 - expansion bus pinout?

[Twospruces]

Considering a project to add an XT-CF card to a Toshiba T1000.

Has this nut been cracked yet?

(as far as XT-CF for Toshiba goes, there is this- https://www.reddit.com/r/retrobattl...ally_finished_my_cf_card_adapter_for_toshiba/ but this is for T1100 not T1000.)

There is some information available-

http://www.minuszerodegrees.net/manuals/Toshiba/Other/Toshiba T1000 - Maintenance Manual.pdf

http://brassicgamer.blogspot.com/2018/11/toshiba-t1000-part-three-technical.html

Just getting started searching for info, but I see that the design includes a 20 pin expansion bus.
PJ 8 Expansion bus connector (20-pin) (not too many pins!)

Has anyone ever figured out what the pinout is for PJ 8?

thx

 

[Andrettigto]

That sounds like a great project. Please update this thread if you get further into it!

 

[Eudimorphodon]

I have a bad feeling that the 20 pin expansion connector only has enough signaling on it to run a modem or other "port-like" device, but unfortunately, yeah, there seems to be zero documentation in the wild for any of the internal connectors.

(FWIW, I have a basket case of an IBM Convertible that I hope to someday build something interesting for if I can find the time, and there are some vague signal descriptions in the Toshiba manual that remind me of how the Convertible does things. In the Convertible the internal modem connector has the 8 data lines multiplexed with the bottom 8 of the lower 10 address lines, along with a single IRQ line, I/O read/write, and a couple of address latch control lines, so with the help of a proprietary demux ASIC in the teeny tiny modem interface board it acts like a low-pin-count subset of ISA. On the south side of that glue ASIC is an 8250 serial chip and the rest of the modem circuitry. In theory there's enough there you could interface a semi-arbitrary I/O device using the one IRQ, but there's no possibility of hanging memory off it. I'd be willing to bet a nickel the T1000 is doing something similar.

The Convertible does have a full expansion bus, but is still actually a huge PITA because instead of demux-ing data and addresses from the 8088 once on the motherboard like, well, almost every other PC in the world, it carries the multiplexed version *everywhere* so every expansion card or module needs to have its own address latches. IBM embedded in *every card* a proprietary ASIC like the one I mentioned above to handle this, presumably to make it just a *little* more difficult for third parties to build expansions.)