Re: Slot settings on a ROM 3

[Pim Blokland <nipp@plane.nl>]

In article <1e4o9dm.12tid8s1taez1yN%dempson@actrix.gen.nz>, 
dempson@actrix.gen.nz (David Empson) wrote:

> > Set slot 3 to "Your Card". ...boot from a floppy that has only ProDOS 
> > and
> > Basic.System on it.
> > Now type :PR#3 (That's PR#3, preceeded by a colon.)
> > This puts you in 80-column mode!
> 
> Can you actually do anything at this point?  Do catalogs, program
> listings, etc. work?

Sure, LIST and RUN work fine. Basic.System does tend to get disconnected 
with a BASIC PR#3, but if you press Esc 8 instead, it will keep working.
Funny thing is that even after you have put the machine in 80 column 
mode, Basic.System will carry on complaining that there is no device 
connected if you type PR#3 at this point again.

> The reason that BASIC.SYSTEM's PR#3 command reported "NO DEVICE
> CONNECTED" is that BASIC.SYSTEM checked for the presence of a card in
> slot 3 before letting the system crash.  (It may have relied on
> information from the ProDOS kernel's global page.)

Yes, it does check SLTBYT. Could be that the way in which ProDOS checks 
for the presence of a card is the right way, and it is the monitor which 
is mistaken in whether there is firmware available at $C300 or not. 
Maybe it's by design: the computer concludes that there is nothing 
present at $C300 and decides to fall through to the built in ROM instead.
Anyway, I don't blame the computer for doing something wrong. If the 
user sets slot 3 to "Your card" while there isn't actually a card there, 
he is not supposed to access $C300 at all. So it's basically my fault.
-- 
Groetjes, Pim

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