[Coco] large HD in OS9/68K

[David]

On Thu, Nov 13, 2003 at 09:02:36PM -0500, David Hazelton wrote:
> Dave Kelly wrote:
> 
> >>>My MM1 drive is set to 33 spt starting with sector 0. So that's 0 - 32.
> >
> >>I wonder if there's any valid reason for starting with sector 0?  It's
> >>apparently an odd setup.
> >
> >Zero is the first number.
> >It is my understanding that machine language and the C language uses 0 as 
> >the first number.  OS9 follows this convention.

Coco OS9 started with 1.  I don't know whether this was MW's doing or
Tandy's.  But it appears that most of our OSK machines start with 0.

> I thought that Microware used the Universal disk format that started at 
> track 0, sector 0 single density. but later modified this due to some 
> Disk controllers could not do this, thus the Sector/Track offset in the 
> descriptors.  Which I would believe those offsets would both be set at 1 
> by default, so every controller could deal with it.

Is it the controller or the OS?  What brought this subject up was the
fact that I couldn't read the disks on my Linux system using fdutils.
>From the documentation I found, a stock Linux kernel cannot read a
0-based sectored disk.  There was a kernel patch which I applied, but
still couldn't do a raw disk copy  (dd - similar to "mergd /d0@ >
somefile" in os9).  However, what I read seemed to imply that you would
still have to maybe do a low-level sector-by-sector or maybe
track-by-track read or write, so I didn't fool with it anymore.

> Maybe this was 
> after done after the original MM1 version of the OS.  I have not looked 
> at the settings on the AT306, but on a VME machine running V2.4 I did 
> look at this as more of a confirmation of what I was reading.

The AT306 begins with sector 1 ?  I'm seriously considering redoing all
my disks to begin with sector 1.  From what I can garnish, these
0-sectored disks are unreadable on a Linux system (not sure about
windows), without jumping through difficult hoops.  I'd like to create
disk images and store them on on CD to preserve them.

I could do a "merge /d0@ > file" on my OSK system, then transfer these
images to my Linux box and burn them to CD like that, but I still
couldn't restore the floppy under linux, and if I lost the ability to
boot on my OSK system - and these floppies are quite unreliable
nowadays - and I'd be out of luck.

But I wonder - would my boot rom be able to read a 1-based sector disk?

Might need to check that out.