Re: Dos CP/M on a Z80 card require an 80 column card to work?

[mjmahon@aol.com (Michael J. Mahon)]

Paul Schlyter wrote:

>In article <qwmdnfRJt9A_5_aiU-KYuQ@comcast.com>,
>Bill Garber <willy46pa@comcast.net> wrote:
>From: "Bill Garber" <willy46pa@comcast.net>
>Subject: Re: Dos CP/M on a Z80 card require an 80 column card to work?
> 
>> "Paul Schlyter" <pausch@saaf.se> wrote in message
>> news:bkfqoi$s9q$1@merope.saaf.se...
>>
>>> The dip switches on the Z80 card may have been set improperly -- all
>>> 4 of them should be set to the OFF position to run Apple CP/M.
>> 
>> Come to think of that. I do need switch 4 set to ON to run it
>> with my 80 column card in place. Sorry that I didn't remember
>> that part.
> 
>Strange --- my Z80 Softcard always worked with an 80-column card with
>all the 4 Softcard dip switches set to OFF.  It's a Microsoft
>Softcard, and the 80-column card was a Videx card.

According to information on the web:

"If your card is a Microsoft Softcard (easily identifiable by the words
"MICROSOFT SOFTCARD" printed in the upper left corner of the component
side), or a clone thereof, then OFF is the correct position for all four
switches (Softcard CP/M doesn't use any of the features that the switches
control).

The Softcard switch settings are as follows:

Switch 1:  OFF = Address translation occurs (Z80 address 0000H corresponds
                 to 6502 address $1000)
           ON =  No address translation (Z80 address = 6502 address)

Switch 2:  OFF = Softcard locks out all other DMA devices when Z80 is active
           ON =  DMA signal from higher slot can interrupt Softcard

Switch 3:  OFF = Softcard ignores NMI
           ON =  NMI causes Z80 non-maskable interrupt

Switch 4:  OFF = Softcard ignores IRQ
           ON =  IRQ causes Z80 interrupt

Softcard CP/M expects to find addresses remapped, so switch 1 should be
left off.  Most Softcard CP/M programs can't handle interrupts, so switches
3 and 4 should be left off too.  Turning switch 2 on probably won't hurt
CP/M, but leaving it off is consistant with CP/M's philosophy of letting
the 6502 handle most I/O."

So all switches should be off.

-michael

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