[Coco] Disk Basic and 512 byte block floppies.

[John Collyer]

See the July 1986 Rainbow article by
Marty Goodman, "CoCo to MS-DOS"
it reads/writes 512 byte sectors on a
MS-DOS formatted floppies.

John Collyer

----- Original Message ----- 
From: "John E. Malmberg" <wb8tyw at qsl.net>
To: <coco at maltedmedia.com>
Sent: Friday, January 16, 2004 9:36 PM
Subject: [Coco] Disk Basic and 512 byte block floppies.


> After reading about how the IDE was supported on HGB dos, I decided to
> try an experiment with ROM BASIC on a COCO II.
>
> I formatted a 720K 3.5 inch floppy with 512 byte sectors on OpenVMS
> because ODS-2 puts some readable ASCII in the first sector.
>
>
> I then put the floppy in the Color Computer, and used the DSKI$ command
> to read the first sector.  The CLEAR 520 command is needed to reserve
> enough string space.
>
> The text string "OPENVMS      is not a system disk" was clearly
> displayed on the Color Computer.
>
> I then did A$="HELLO FROM COLOR COMPUTER", and used the DSKO$ command to
> write it to the disk.
>
> Placing the Floppy back in the OpenVMS system and examing the first
> block resulted in me seeing the same text.
>
> So it appears that it should not be too hard to patch DISK basic to deal
> with 720K 512 byte blocked media.  Either simply using them at 1/2
> capacity, or remaping the sectors beyond 9 to the other side or to
> tracks beyond 35.
>
> Clearly more experiments are in order, but if a standard method of
> remaping the sectors were developed, it would allow emulators on most
> platforms to directly interchange floppies with the Color computer.
>
> At the minimum, it appears that I can use a BASIC program to write on
> floppies that are readable on OpenVMS in a RAW form.  Which means it
> will easily work on LINUX/UNIX also.
>
> There is documentation on the wild wild web for Microsoft Windows to
> directly read and write to 512 byte media also.
>
> -John
> wb8tyw at qsl.network
> Personal Opinion Only
>
>
> EAGLE> init/dens=dd dva0:
> _Label: OpenVMS
>
> EAGLE> MOUNT/FOR DVA0:
> %MOUNT-I-MOUNTED, OPENVMS mounted on _EAGLE$DVA0:
>
> EAGLE> DUMP DVA0:/BLOCK=(START:0,COUNT:1)
>
> Dump of device DVA0: on 16-JAN-2004 17:01:46.09
>
> Logical block number 0 (00000000), 512 (0200) bytes
>
>   03039401 001E65C0 11C00200 15C600A0 ..Æ...À.Àe...... 000000
>   8BDFFF76 905F0000 000501FB 000609F7 ÷...û....._.v.ß. 000010
>   20202053 4D564E45 504F0087 80FDFF74 t.ý...OPENVMS    000020
>   73206120 746F6E20 73692020 20202020       is not a s 000030
>   0000000A 0A0D6B73 6964206D 65747379 ystem disk...... 000040
> EAGLE> DISM DVA0:
>
> Disk removed and placed in Color Computer and then returned.
>
>
> EAGLE> MOUNT/FOR DVA0:
> %MOUNT-I-MOUNTED, OPENVMS mounted on _EAGLE$DVA0:
>
> EAGLE> DUMP DVA0:/BLOCK=(START:0,COUNT:1)
> Dump of device DVA0: on 16-JAN-2004 17:15:20.50
>
> Logical block number 0 (00000000), 512 (0200) bytes
>
>   524F4C4F 43204D4F 5246204F 4C4C4548 HELLO FROM COLOR 000000
>   00000000 00000052 45545550 4D4F4320  COMPUTER....... 000010
>   00000000 00000000 00000000 00000000 ................ 000020
>
>
>
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