From: Mike <dogas_at_bellsouth.net>
Date: Mon Jan 28 13:28:31 2002

From: Ethan Dicks <erd_6502_at_yahoo.com>
> > > That sounds wicked. I wonder how they handled the 12-bit bus of the
> > > 6100.
> >
> > pins 19-22 on the standard OSI bus = A16 - A19 for extended addressing
> > under the 6502 (multiuser and under software control of the PIA) and
> > probably used natively under the 6100...
> The 6100 has a 12-bit address bus (and presumably 3 bits of address
> extension - EMA bits, as they are called on the PDP-8) *and* a 12-bit
> data bus. _That's_ the one I was wondering about. For the address
> stuff, externally, you can pretend that it has a 15-bit address bus,
> and you won't have too many gyrations to perform. Where to stash the
> extra 50% of data when you are sharing a box with a bunch of 8-bit
> processors is the question.
> I suppose you could design a buffer that performs two memory transactions,
> one for D0-D7 and one for D8-D11, and write into a 64KB address space,
> but personally, I'd rather design in the room for it. If the 6100
> card had its own RAM, but you only permitted 8-bit I/O transfers, that
> could resolve the problem, presuming you didn't have to have shared RAM
> for the handoff scheme...

OSI bus is 12bit address and data. Pins 13 -16 = D8 - D11, but I don't know
anythng about the EMA bits or RAM use under the 6100. I'll look through
what I have.
Received on Mon Jan 28 2002 - 13:28:31 GMT

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