OT-ish: Build-it stuff

Chuck Guzis cclist at sydex.com
Wed Jun 14 11:54:07 CDT 2006

Having unknown hardware in your hands isn't, IMOHO, nearly as bad as
unknown software.  Consider my conundrum right now...

I've got a diskette with software (no documentation beyond how to stick it
in the slot on the machine) for a computer that a customer wants to emulate
on a PeeCee, the last remaining sample of the original hardware having
flown the coop.  No engineering documents at all.  The instruction set
(from the disk) appears to be 8086, but the OS is unknown to me and from
the looks of it, the disk is loaded into memory as a single 240K image.  I
can figure out the load address by explicit segment references.  From the
very few ASCII text strings in the code, this is apparently a
multithreaded, interrupt-driven OS.

>From the scant documentation, the box came with a keypad, an LCD(or plasma
or some-such) readout and a diskette drive with an RS-232 port.  Otherwise,
ASCII searches yeild no error messages, prompts, or anything that would
allow me to quickly determine control flow.  I have absolutely no idea of
the peripheral configuration.  This is circa 1981-82.

So, where do I start?  I could put it on an emulator and attempt to trace
program flow, but given the nature of the OS (event-driven) it's not going
to be easy.  I can locate a few ISRs, and from their appearance, the box
doesn't use an 8259 PIC (no EOI sequences at the end of the ISRs).

If this were a hobby thing, I wouldn't care about the time I put in--but
the customer wants a quote.

Any suggestions?


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