[Coco] Pokes for DECB to allow Single density 35 Track Disks to be Formated and Backed up?

[Robert Gault]

The answer is both yes and no, not what you want to hear and it may 
depend on the structure of the FLEX disks in question.

Obviously a Coco can do what you want when running FLEX. I'm not sure 
whether Coco FLEX conforms to the IBM 3740 format standard of 128 bytes 
per sector or even if your disks are Coco FLEX or some other type. The 
nature of your disks will determine the easy of patching with POKEs or 
whether you will need to write some ml routines.

The DOS1.1 ROM has the format track data at $D6D4-$D6EB. The byte 
controlling the sector size is at $D6E6 default 0=256. It will need to 
be $80=128 for 128 byte sectors. DSKCON initializes the disk controller 
for double density at $D774 ORA #$20. That will need to be changed to 
single density ANDA #not$20 or $DF.

After the above changes you should be able to read/write single density 
128 byte sector disks. However, the disks will be uniform throughout 
with the same number of sectors per track as a Disk Basic disk. If you 
want to change the number of sectors per track, there are at least 8 
locations in the ROM that need to be changed. If you want to change 
track and sector density along with sector size on a flexible basis, you 
will have to write your own format and disk I/O routines. I strongly 
suggest that you consult "Unravelled" series of books and study the 
related stock routines before writing your own ml replacements.

Stephen H. Fischer wrote:
> Hi,
> 
> Are there pokes for DECB to allow Single density 35 Track Disks to be
> Formatted and Backed up? Setting Sectors per Track?
> 
> This would allow for FLEX disks that are entirely Single Density to be
> backed up.
> 
> FLEX also has mixed density type disks which I assume cannot be backed 
> up by
> DECB. DECB will backup OS-9 Double Density 35 or 40 Track disks if patched
> as it does not look at the data during the backup process.
> 
> I found that all of my FLEX disks are readable even after sitting unused 
> for
> decades. So I am copying the files on them to OS-9 disks for backup onto
> CD's.
> There are some files that must be placed at fixed places on the FLEX boot
> disk which will not occur by just copying the files. And formatting new
> blank disks would be a great bonus.
> 
> Any ideas as to how to save a FLEX disk using DECB or OS-9?
> 
> 
> TIA
> 
> Stephen H. Fischer
> 
> 
>