aiiadict{at}gmail.com wrote:
> On Nov 24, 7:40 pm, Steven Hirsch  wrote:
>> Neither the Applicard nor CardZ180 used DMA for transfer between host and
>> guest processor.  They both relied on programmatic transfer.  For
example, the
>> Z80 writes a byte to a port and polls a status bit to see when it can write
>> the next one.  6502 checks a status bit on its side and reads the
byte from a
>> memory address when it's ready.
> 
> Yeah I'm reading more about the cards since this thread was posted...
> 
> Even video data is transferred this way....  Did any of the z80 cards
> have their own video OUT connector?  Seems like a really slllloooowwww
> way to go about updating the screen.

Vapor-ware wise, I found a diagram for a video piggyback board in a packet of 
stuff from the CardZ180 designer.  I don't know if any hardware ever existed 
and I know that no software did.

More practically, the CardZ180 had two high-speed UARTs built in and could 
connect directly to a terminal or terminal emulator at 38.4K Baud.  Ray Klein 
designed a nice UART piggyback board for the Applicard for the same purpose. 
There are a few of those in the wild.

BTW, the console output on a CardZ180 is about 2x faster than the Applicard 
due to both improved hardware and some optimizations to the transfer protocol. 
This is particularly noticeable on an accelerated IIGS or a //e with a 65C802 
equipped Transwarp card.  I wrote a host-side display driver that used the 
block transfer instructions on the 802 and 816 for more efficient scrolling. 
Even on a stock //e, screen performance was quite snappy.

The CardZ180 Z-System environment supported Bridger Mitchell's BackGrounderII 
software.  This was a simple but powerful task switcher similar to Borland 
Sidekick (I'm dating myself now).  A hot-key would freeze the foreground 
application and switch the console to BackGrounder's utility screen.  You 
could switch between multiple live CP/M applications, although only one was 
actually active at a time.  We could even save/restore high resolution text 
consoles on a Videx Ultraterm (132x55 text screen!  Neat for word processing).


Steve
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