[Coco] FAT vs. FAT

[Willard Goosey]

>Date: Mon, 29 Jan 2007 11:22:49 -0600
>From: Joel Ewy <jcewy at swbell.net>

>The whole thing would be simplified if I could just write individual
>files on a DOS formatted floppy on the PC and read them on the CoCo,
>or vice-versa.
>
os9.exe & the toc/fromc package under DOS, the pcdos program under
NitrOS9.  Toolshed + fdutils under Linux.

You're running Windoze?  Sorry, Bill Gates doesn't want you to go
there today.

>Ok, so I know that there are similarities, and significant differences
>between the DECB FAT file structure and the MS-DOS FAT file structure. 
>256 vs. 512 byte sectors is one difference.  Numbers of sectors per
>track, and tracks per disk, and sectors per allocation unit, et cetera. 

...number of bits/FAT entry, number of FATs, which track they're
stored on...

>My guess is that the main challenge for doing such a thing on the CoCo
>would be ensuring that there is sufficient RAM for the data structures
>needed to implement a more generalized FAT system, and more importantly,
>wedging those data structures into BASIC's not-so-easily modified memory
>map.

Muck with the DECB filesystem and you'll break every program that does
its own manipulations on the disk... Which is probably most DECB
programs because DECB's so limited in what it can do itself.

>In OS-9 a more generalized FAT
>file manager that could also handle both CoCo FAT and MS-DOS disks would
>be much easier to implement, I think, at least in that you don't have to
>worry about stepping on BASIC's data structures.
>
There are, however, fairly strict limits on the size of an OS-9
kernel.

>Thoughts, ideas? (aside from "Get DriveWire".  :)  One of these days I
>will.)

As someone who's spent most of the day trying to get a computer to
read just one foreign disk format.... good luck.  

I suggest you start by digging up the technical docs on the DOS FAT.
Once you grok it, then you can start coding.

Willard
-- 
Willard Goosey  goosey at sdc.org
Socorro, New Mexico, USA
"I've never been to Contempt!  Isn't that somewhere in New Mexico?"
   --- Yacko