Re: Later Apple II Technical Manuals

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

Great Hierophant wrote:
> There is another minor change between the Enhanced IIe and the Platinum
> IIe boards, there is only one ROM in the Platinum IIe as opposed to the
> two ROMs in the Enhanced IIe.  One less chip or circuit for
> multiplexing.

As long as we're cataloging circuit differences, the Platinum and
later //e's also had a minor modification to the pushbutton inputs
which has major effects on their usability as general digital
inputs--Apple decided to parallel the inputs with 0.1 microfarad
capacitors, apparently in the interest of reducing EMI when a
joystick is plugged in.

This also reduces the effective bandwidth of the pushbutton
inputs to about the level of a, well, *pushbutton*, making
them useless for faster signalling unless the capacitors
are removed.

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

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