Re: Questions about IIGS, hard drives, and booting different OSes...

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

Warren Ernst <wernst@gmail.com> wrote:

> Andy McFadden wrote:
> > Warren Ernst <wernst@gmail.com> wrote:
> > > Andy, your setup of booting into ProDOS 8 and then using ProSEL too
> > > fire up GS/OS is about what I had in mind (I've been a hardcore ProSEL
> > > 8 user for decades.). But tell me, is there any reason I couldn't
> > > install GS/OS on the second partition and launch it from ProSEL this
> > > way? I can't think of any reason why not...
> >
> > I don't know.  Haven't tried it that way.  Seems like it should work.
> 
> Well, it doesn't seem to work.
> 
> I have ProDOS 8 on the first partition. I installed GS/OS 6.01 on the
> third partition. I've renamed the PRODOS file from GSOS to PRODOS.GSOS
> as directed.
> 
> No matter how I execute PRODOS.GSOS (launcher, basic program, direct
> command from the basic prompt), I always get the error:
> 
> Unable to load START.GS.OS file. Error=$0046

That's a File Not Found error.

My recollection is that GS/OS is restricted to booting from the first
partition. GS/OS's "PRODOS" bootstrap loader contains minimal drivers
that only support accessing drive 1 of the slot from which GS/OS is
booting. Once START.GS.OS is running and it gets the proper GS/OS
drivers loaded or generated, it can access all drives.

You might be able start ProDOS-8 from a different partition, but not
GS/OS. Even ProDOS-8 might look on the first partition for the startup
.SYSTEM application.

The only way I know to do a dual-boot GS/OS system (e.g. System 5 and
System 6) would be to install them both on the first partition with
various files and folders being renamed as required to boot the correct
system. I assume this is what TaiFunBoot does.

It has been a while since I looked into this, but I think the
fundamental problem is that there is no information available to the
PRODOS bootstrap loader which tells it the drive from which the file was
loaded. It can find out which slot was being used courtesy of some zero
page variables left behind by the block 0 bootstrap loader (which have
to be replicated if the PRODOS file is launched directly).

Assuming I'm right, the only way to boot GS/OS from another partition
would be to load GS/OS's PRODOS bootstrap loader into memory and patch
it to access a different drive. Since it probably uses the ProDOS block
driver supplied by the slot firmware, even this technique would be
limited to drive 2 except in special cases. It would have to use the
SmartPort firmware driver to access higher drives, and GS/OS can be
booted from devices which don't have SmartPort support, such as the
RamFast, so I doubt the GS/OS bootstrap loader attempts to use
SmartPort.

-- 
David Empson
dempson@actrix.gen.nz