🚀 go-pugleaf

In article <1992Nov21.161430.14520@r-node.gts.org> taob@r-node.gts.org (Brian Tao) writes:
> In article <1992Nov21.072442.19093@actrix.gen.nz> David.Empson@bbs.actrix.gen.nz writes:
> >
> >That is the least of the problems.  As Jawaid mentioned, ProDOS-8 and
> >GS/OS reside in the same areas of RAM (language card in bank 0).
> >
> >GS/OS also uses a large chunk at the top of bank 0, the top of bank 1,
> >and all the language card space in bank 1.
> >
> >There may be interrupt handlers within GS/OS device drivers sitting
> >there waiting to do GS/OS system service calls
> 
>     So what happens when you normally run a ProDOS 8 program from GS/OS?
> From the way you describe it, things like the Desktop Utilities screen
> blanker and Prosel-16 Appointment Calendar would be disabled, but they
> still work.

I'm talking about GS/OS components here, not desk accessories.  When
GS/OS switches to ProDOS-8, it copies itself out the bank 0 and 1
language cards, releases all other memory it is using in banks zero
and one, and shuts down all the device drivers (disabling interrupt
handlers in the process).

CDAs aren't affected (but can no longer make GS/OS calls while
ProDOS-8 is active), nor are heartbeat interrupts, etc.

ProDOS-8 is then loaded into Bank 0 and made to launch the appropriate
program.

When returning to GS/OS, the process is reversed - ProDOS-8 is copied
elsewhere (so it can be restored quickly on the next entry), GS/OS is
reloaded into bank 0 and 1 language cards, buffering memory, etc. is
reallocated and the drivers are reopened.


The big danger is device drivers, particularly with I/O cards such as
the SCSI card or 3.5" Drive Controller card, both of which may have
been patched in some way by the GS/OS drivers, and have to be
un-patched for normal use with ProDOS-8.

Device drivers may also try to call GS/OS system service vectors (in
bank $01 language card space) from heartbeat interrupts (or
elsewhere), unless they've been shut down by GS/OS.
-- 
David Empson

Internet: David.Empson@bbs.actrix.gen.nz    EMPSON_D@kosmos.wcc.govt.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand