Re: IIgs ROM 01 & Z80+

[D Finnigan <dog_cow@macgui.com>]

"Michael J. Mahon" <mjmahon@aol.com> wrote:
> On 10/5/2010 5:19 AM, KP wrote:
>> On Oct 5, 8:00 am, Steven Hirsch<snhir...@gmail.com>  wrote:
>>> On 10/04/2010 11:20 PM, Michael J. Mahon wrote:
>>> 
>>>>> 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.
>>> 
>>> Thanks for keeping me honest.  I'm not really a hardware guy and
> > > don't keep
>>> this stuff in my forebrain :-).
>>> 
>>>>> 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. ;-)
>> 
>> So is the final verdict on this that the card should work on a //e
> > but
>> it's no surprise if it doesn't work on a IIgs ROM 01 (even at 1 mHz)?
>> Or should I be concerned that the card is defective?
> 
> The IIgs is definitely not guaranteed.  But unless the Z80+ was
> designed
> after the //e, even the //e is not guaranteed.
> 
> //e bus timings were somewhat different than ][ and ][+ timings

Not trying to be too contradictory, but doesn't the IIe tech ref man say
that the IIe timing was made intentionally a bit "off" to be more
compatible with the previous models?