Re: Apple IIc Booting from external drive

[zcaa1122@rpool4.rus.uni-stuttgart.de (Wulf Hofbauer)]

In article <1993Jun5.051443.7547@actrix.gen.nz> dempson@swell.actrix.gen.nz (David Empson) writes:
>
>The original IIc ROM lets you boot ProDOS from an external 5.25" drive
>by typing PR#7.  You can't boot DOS 3.3 or Pascal using this method.
>
>All subsequent versions of the IIc (which add UniDisk support) have
>this feature removed.  If my copy of the IIc hardware reference manual
>is to be believed, you can boot from the first external drive by typing
>PR#5.  I suspect this only applies to a UniDisk 3.5, and not a 5.25"
>drive.

Actually, you can boot from an external 5.25" driver on the //c with ROM
revision 2. The code necessary is in ROM (the ROM listing comments even
tell that you can do it), but due to some omission you can't activate it
by a single command.

You can boot however from the external driver by hacking in a short machine
program. All you have to do is set X to $60, Y to $01, and A to $e0 and
jump do some address... was it $c611? Take a look at the listing...

Oh, yes, it is fun to boot from the external drive as mine has a track zero
sensor and is much more quiet :-)

- Wulf