Re: Apple II bus breakout board

["Michael J. Mahon" <mjmahon@aol.com>]

ferdimh@gmx.de wrote:
> I'm unable to see the pictures... your server seems to be down.
> Such a breakout board is a nice idea.
> But I'd include buffers for all signals and fuses for the powers to
> protect the Apple 2.

Buffers are problematic for 2-way signals, and in any case
modify the electrical interface so that a card designed to
work on the other side of the buffers may not work properly
when installed directly on the Apple bus.

Best plan for prototyping is to keep any bus extension to
a few inches (like an extender card) and don't put any
extra electronics between the bus and the prototype card.

> And I'd use a 68-pin cable where I'd put the power lines between the
> high freqency signal lines:
> 16 address, 8 data, 3 strobes, R/W, 4 clocks and 2 interrupt signals
> yield 34 pins. the other 34 should be reserved for power. This way
> interference between adjacent wires is reduced allowing a longer cable
> length.

FWIW, I've successfuly operated many (not all) Apple II cards at
the end of a 50-wire ribbon cable about 30" long.  No buffering or
crosstalk protection was required, and only the usual power bypassing
on the card itself.

Most cards for the Apple are amazingly robust and tolerant of
extra wire (though the disclaimer about perturbing timing and
edges with buffers above still applies in general).

-michael

NadaPong: Network game demo for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

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