Re: Multi-Tasking on Apple IIgs?

[et472@FreeNet.Carleton.CA (Michael Black)]

David Wilson (david@uow.edu.au) writes:
> The Wizard of Oz <wizard@emeraldcity.gov> writes:
>>	I was going to ignore this thread until I thought about the possibility
>>of co-processor cards. If a co-processor card could be active the same
>>time as the GS processor then you could get true multi-tasking as opposed
>>to the time slice mechanism everyone else is suggesting.
> 
> It depends on the type of co-processor card. A Stellation Mill with a
> 6809E chip can run a program while the motherboard CPU runs another program
> but as both are using the same RAM on the motherboard they still time slice
> (just at a much finer level than an interrupt driven pre-emptive multitasking
> system) with the 6502 only running during cycles when the 6809E does not need
> to use the data bus.
> 
> Do any co-processor cards for the Apple II family have on-board RAM allowing
> them to run completely independently of the motherboard (apart from I/O)?

I think the 16-bit CPU boards would tend to have onboard memory.  There
was the fancier Z-80 card that had memory onboard.  I thought there was a
second 6809 card that had onboard memory.

BUt most of those boards took over the computer.  They weren't really about
doing two things at once, but about adding power and using the Apple as
a terminal (and for the other I/O).

There was that DTACK Grounded board with the 68000, and wasn't it
introduced as a math speed up board originally?  But while it would
do the math fast, then it has to slow down and interface with the rest
of the hardware and software.  There is a very limited return.  And
like computers today, you get a situation where speed looks impressive
"I've got a 1GHz computer" but since the rating applies only to the CPU
speed it's misleading;  the rest of the computer is much slower and so
the speed increase is only incremental.  When I sped up my OSI Superboard
years ago, I did indeed double the speed when I cut a trace and added
a jumper to have the CPU run at 2MHz rather than 1MHz.

  Michael