[Coco] hybrid CoCo-CP/M disk

[Robert Gault]

Willard Goosey wrote:
>>Date: Sun, 14 Jan 2007 09:04:23 -0500
>>From: Robert Gault <robert.gault at worldnet.att.net>
> 
> 
>>Not sure what you mean in the above by "group 0x4a". If that's gran $4a, 
> 
> 
> And here I thought I was being careful to use "group" to describe a
> CP/M allocation unit and "granule" for a CoCo allocation unit...
> 
> Anyway, like the other guy already said, that was referering to the
> CP/M filesystem, such as it is.  
> 
> And I do also have to make a correction: Group 0x4A starts at track 34
> sector 17, not track 17 sector 17.  This is probably what confused
> you?
> 
> It's right on the disk, I just got confused talking about it later.
> 
> For this particular CP/M disk format, tracks 0 & 1 are reserved for a
> boot image (rather there's one there or not), and so the "groups" of 8
> sectors starts on track 2.  Groups 0 & 1 are the directory, and the
> rest of the disk is data.  As I noted, this does not come out even on
> an 18 sector/track disk.  
> 
> Willard

After it was pointed out to me that "group" referred to the CP/M disk 
structure, I looked up info on CP/M on the Web. There seems to be as 
many different disk structures as there were computers that used them; 
10 formats listed just for TRS machines. Which format are you working with?

At least one Coco software package uses the entire track 17. RGB-DOS 
used the last sector of T17 for a disk label. I think some software may 
have stored a copy of the FAT or perhaps the entire directory in the 
latter half of T17.