Re: Apple IIc Booting from external drive

[ddkilzer@iastate.edu (David D Kilzer)]

>kevins@donald.ee.pdx.edu (Kevin Stanton) writes:

>> It says ''cannot read disk'' when trying to boot up.
>> I tried pr#6,2 but it still spun up drive A.
>> Is there a way to bypass this?

dempson@swell.actrix.gen.nz (David Empson) writes:

>Possibly.

>First, find out which version of IIc you have by typing PRINT PEEK(64447).
>If it says 255, you have the original IIc ROM.  Other possible values
>are 0, 3 and 4.

>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.

Yes, PR#5 will boot the first external UniDisk in the //c's drive chain.

I recall typing in a small segment of assembly code (from inCider/A+,
Nibble, or some such magazine) that would boot the external 5.25" drive,
even if you had a //c with newer ROMs.  I don't *think* it worked on
anything but a //c, but I can't remember for sure.  If you'd like me to
dig it up and post it to the 'net, email me.  I'm sure I can find
it...it's only a matter of digging through a few of my BASIC programming
disks.  :^)

>Why do you want to boot from the external drive?  Is your internal one
>faulty or something?

Yes, that's one of the better reasons to do it.  Of course, if you're
REALLY ambitious (and don't mind voiding the warranty on your computer
and disk drive--that is, if there's still one in effect), you can remove
the cover from the //c and from the external disk drive (as long as it's
an Apple External Disk Drive //c), and "swap" the drives.  I don't
recall if you could put the //c case back on or not.  I seem to recall
that the keyboard needed a small notch in the side of the disk drive
housing for the //c to go back to gether again, but you can certainly
switch them while doing some troubleshooting.

Dave
-- 
David D. Kilzer               \                ST:TNG _Relics_
Computer Engineer 3           /       Capt. Montgomery Scott ("Scotty")
ddkilzer@iastate.edu          \   "I may be a captain by rank, but I never
Iowa State University, Ames   /    wanted to be anything but an engineer."