Re: IIgs ROM 01 & Z80+

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

On 10/4/2010 6:07 PM, Steven Hirsch wrote:
> On 10/04/2010 08:48 AM, KP wrote:
>
> > > > The traditional softcards played very fast and loose with timing
> > > > margins at
> > > > best. I'm actually more surprised at the fact that it _ever_ works
> > > > reliably
> > > > in a IIGS!
> > >
> > > So you're saying I need to just use it with a //e?
> >
> > Also, should I anticipate any problems running a TransWarp and a Z80+
> > simultaneously? Does the speed setting of the TransWarp matter in
> > this regard?
>
> A TransWarp as in Apple 2e? I seriously doubt that will work. The Z80
> card shares motherboard memory with the system CPU by stopping the 6502
> (ISTR this is via INH\, but that may not be correct). At any rate, the
> IIe TransWarp does exactly the same thing on a permanent basis so they
> are not going to coexist very well.

I think it uses the /RDY line to halt the 6502.  That's one reason that
it won't work with a Zip Chip.

> Tony mentioned the need to run at 1Mhz. in another posting. That's a
> hard requirement for proper functioning of a SoftCard style coprocessor.
> It truly was a bit of a hardware hack. I have three or four SoftCards
> and perhaps a half dozen AE Z80+ cards. Some will work in some systems.
> None of them will work in all of my systems. One more reason to keep on
> the lookout for an Applicard if you're serious about Apple CP/M. Never
> found a box that an Applicard wouldn't work in and it coexists with any
> and all accelerators on both IIe and IIgs - at high speed settings, too.

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.  ;-)

I think that the simplicity of interfacing to the Apple ][ and ][+ led
designers to be rather cavalier about bus timing and testing.  I'll bet
that only a handful of Apple II cards were ever tested for their actual
bus timing margins (say, with a "doctored" Apple II testbed).

It's actually quite remarkable that so many cards ran reliably on so
many systems that they hadn't been tested on.

-michael

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