Re: Multitasking apple II

[Andy McFadden <fadden@fadden.com>]

Simon Williams <bill_gates@microsoft.com> wrote:
> Okay, here's a thought... 8-bit Apple IIs are expandable to 1.125 MB but
> aside from Appleworks, most 8-bit software is quite happy running in 64K
> or 128K. Would it be possible to hack Prodos to swap 128K at a time
> without quitting the current program?
> I imagine this would require the OS to take a "snapshot" of the
> currently running 128K and move it up, and then move a different 128K
> bank into main memory.... maybe this is similar to how Proterm is able
> to switch between terminal and editor.


I used to swap ProDOS 8 itself in and out for the 64K version of ProDOS
RDOS.  It was a little slow on text files, which RDOS liked to read a byte
at a time, but otherwise worked.  (Speed enhancements were planned, but
the project was never finished.)  The real trick is you have to disable
interrupts while ProDOS is swapped out, or anybody with a P8 AppleShare
network running is going to be deeply unhappy.

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