Re: IIgs ROM 01 & Z80+

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

D Finnigan <dog_cow@macgui.com> wrote:
> "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?

That was the plan, but different is different.  What is "compatible" for
some cards doesn't work for others. 

-michael  -  NadaNet 3.1:  http://home.comcast.net/~mjmahon