Re: Apple iic DiskDrive

[dempson@actrix.gen.nz (David Empson)]

Matthias S�llner <soellner.matthias@t-online.de> wrote:

> Can I boot from an external Disk Drive?

Only in some circumstances.

In the case of an external 5.25" drive, you can only boot from it if you
have the original IIc firmware: PRINT PEEK(64447) displays 255.  You can
use the PR#7 command to boot from the drive.

I think that this will only work properly for a ProDOS disk.  If you try
to boot a DOS 3.3 or Pascal disk in the external drive, I'd expect it to
get some way through the boot sequence then try to switch back to the
internal drive for the rest of the boot.

Later firmware revisions removed all support for booting from an
external 5.25" drive.

In the case of an external 3.5" drive (UniDisk 3.5), you need a later
IIc firmware revision to support the drive at all: PRINT PEEK(64447)
must display 0, 3 or 4.
You can boot from an external 3.5" drive using PR#5, or by booting
normally with no disk present in the internal 5.25" drive.

> Can I boot without an internal Drive?

Assuming you mean "boot from a 5.25" disk without an internal drive",
then the answer will depend on which firmware revision you have - see
the first answer above.

If I'm right about the external 5.25" drive boot (in the original
firmware) only supporting ProDOS, then there will be quite a lot of
software that you won't be able to use if your internal drive is faulty
or has been removed.