[Coco] Re: [Color Computer] DSK images to coco

John E. Malmberg wb8tyw at qsl.net
Sun May 1 12:29:06 EDT 2005

Phill Harvey-Smith wrote:
> George Ramsower wrote:
>>How do I write this to a floppy using my CC3 and OS-9 L2?
>>The B09 program is set up for smaller disks, the MSDOS program won't write
>>to a floppy on this DOZE box.
> I don't think any of the CoCo/Dragon disk writing programs will work 
> under any NT type Windows (NT/2000/XP/2003), because there is no way of 
> programming them to deal with 256 byte sectors. However I believe 95/98 
> & Me don't suffer from this problem.

Windows NT 4.0 and earlier still support the documented APIs to 
read/write 256 byte sectors.

Windows 95 and 98 also work, but I am getting unexplained read errors 
Windows 98.

On the other hand, I have discovered that the COCO under ROM BASIC and 
read and write the first 256 bytes of the 512 byte sectored media. 
Actually it can read and write the full 512 bytes if you use peeks and 
pokes.  The upper 256 bytes are in the read/write verify buffer.

ROM basic does not know about sector sizes and does not appear to keep a 
count of how many bytes are being transferred.  Since the two buffers 
are adjacent and the second one is usually not used, a clever programmer 
could find a way to do either one of two things:

1. Produce a host based program that can setup and populate a 512 byte 
sector floppy that ROM basic can read.  I only see a problem on the 
directory track.

2. Use custom programs on both the host side and the COCO side to 
interchange programs on 512 sectored media, and possibly a consensus can 
be found for the format to use.

It also indicates that a program can be written using the ROM BASIC 
calls that can read and write PC format disks.

Which brings up other possibilities.

Personal Opinion Only

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