Re: IIgs ROM 01 & Z80+

[mdj <mdj.mdj@gmail.com>]

On Oct 5, 1:20 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:

> All the "Softcard-derived" Z80 cards used a syncopated 3.5MHz clock,
> which was regarded even at the time as a major hack.  Like some other
> cards, it has tight bus timing margins, and so running it on a system
> other than one it was tested in during design is actually running a
> reliability test.  ;-)

We probably have the softcard to thank for keeping the later Apple
II's relatively close to the original in terms of bus timing. Whilst
card designers probably did only limited compliance testing, you can
be sure Apple did a lot :-)