[Coco] Floppies to PC or other OSs (was: Issues with 26-3022 interface)

[Gene Heskett]

On Wednesday 13 February 2013 13:21:33 John E. Malmberg did opine:

> On 2/12/2013 9:26 AM, Daniel Campos wrote:
> > Hi Mark,
> > 
> > I understand your point, as this subject have probably been talked on
> > this list many times over. But my main purpose is to pass disk images
> > from a PC (through emulator or some other program) and run them on the
> > Coco. I don't have any legacy 5 1/4 disks to worry about, so if I can
> > do this work on a 3 1/2 floppy, for me is the best choice.
> > 
> > I will try now to transfer some images from the PC to this disks and
> > let's see how will it work...
> 
> Most typical 1.44 3.5 inch drives will work fine as a 720K drive in
> unmodified COCO computers.  That has been known for years.
> 
> Using 1.44 Media at 720 K is iffy, and your mileage will vary.
> 
> If you have Windows 98 or earlier, it is easy to implement a DISK
> utility to read/write coco disks with 256 byte sectors.  Several exist.
> 
> They also appear to exist for Linux.
> 
> With Windows/XP and later, Microsoft removed the API for setting the
> floppy sector size.
> 
> However, any unmodified COCO disk controller with any DISK basic ROM is
> quite happy to read and write 512 byte sector disks, as long as you have
> READ and WRITE verification off.
> 
> The BASIC routines can only access the first 256 bytes of the sectors to
> read and write, but you can access the rest with PEEK() AND POKE().
> 
> The trick is that the COCO allocates 256 bytes for read, 256 bytes for
> verify, and then 256 bytes for write and 256 bytes for write verify, all
> contiguously.
> 
> The COCO DISK ROM disk read/write routines do not count sectors, they
> just read or write bytes until the controller interrupts the computer at
> what ever the sector boundary is.  Since there is 512 bytes of buffer
> already available, it is simply a matter of transferring data in and
> out.
> 
> Which means that by playing some games with the bad sector table, you
> can probably have a PC or other device make a 512 byte sector disk that
> the COCO can do a directory of and read / write to.  You will only get
> 1/2 the capacity of one side of the disk accessible from the COCO ROM.
> 
> It also means that you could write a COCO Basic program to read and
> write a 720K FAT formatted floppy if you were so ambitious, which means
> no special program on the PC.

That is already available as the os9 utility 'pcdos', no real use in trying 
to re-invent that wheel in basic.  You can, and I have done it, use pcdos 
to extract from the fat disk, and then rsdos to put it on a rsbasic disk. 
All from os9/nitros9.  Or voice versa also works.

> Regards,
> -John
> wb8tyw at qsl.network
> Personal Opinion Only
> 
> 
> 
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Cheers, Gene
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