Re: [Vaporware alert!] Portable Apple II Clone Concept


Michael J. Mahon wrote:

True, but reimplementing the Woz machine is not trivial, and using
a Disk ][ Controller would be kind of a tribute to a virtuoso design.
;-)

Indeed. It also gets around the problem of hard to find DB-19
connectors :-)

I guess I envisaged just shifting the state machine into the PIC, which
should be simple enough by simply replicating the logic in software,
and using the PIC's other outputs to control motor on/off and stepper
motor phases. Using the whole card would require a fair number of I/O
pins from a micro, by the time you connected up the data bus plus
sufficient address lines, and then you still need to generate a clock
signal for it, but I guess that's simple enough circuitry. I'd say
either approach is about the same about of work.

It would, however, look really really cool having a little box with a
PC connection + a 50 pin card edge connector sitting exposed on it's
top surface ;-)

The design serves other purposes too - it could just as easily drive a
UniDisk 3.5" - good for transferring IIGS titles or moving larger
amounts of data to a real Apple II.

I guess you know you're a member of the oily hand brigade when this
idea seems infinitely more appealing to a few days hacking Copy ][+ to
write to an image file as its destination media ;-)

That would be pushing 8KB, which I think of as a little large for
most PICs. It would take an external SRAM.

Yes, although there are PICS that large, there are also cheap and
cheerful serial SRAM chips that would do the job.

I got as far as running a Disk ][, seeking the head, and trying
to read the head signal before finding that I couldn't read it fast
enough. ;-(

I wonder it this was an artifact of PC's being a lot slower a decade
ago, or some inherent limitation. I guess in a modern PC the parallel
port still hangs off a virtual ISA bus for compatibility, but I'm
unsure if this virtual bus still clocks along at 8Mhz

In any case, it might be worth checking out the throughput of
USB-Parallel dongles; these things might allow significantly higher
performance.

Matt

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