D. P. Johnson -- SDisk/SDisk3 Floppy Disk Drivers

SDisk is an improved floppy disk driver module for OS-9 that replaces the CCDisk module in the OS9Boot file provided with OS-9 Level I for the Radio Shack Color Computer (CoCo 2). SDisk3 similarly replaces the CC3Disk module in OS-9 Level II on the CoCo 3. The matching SFormat program replaces the original Format program.

SDisk and SDisk3 features:

The new direct sector read/write functions allow software such as the PC-XFER Utilities from D. P. Johnson, and the MSF file manager from Clearbrook Software Group, to access disks that use formats other than OS-9, such as CoCo Disk Extended Color BASIC (DECB), FLEX, MS-DOS, and CP/M.

I licensed the SDisk and SDisk3 drivers and SFormat program from D. P. Johnson, then modified them for my ST-2900 and DMC products.

On 2013-May-31 D. P. Johnson (Dan Johnson) gave me permission, via e-mail, to release the source code and binaries of his SDisk and SDisk3 drivers as free software.

The four disk images available below are as I received them from D. P. Johnson in 1984-1987, except for adding copyright and licensing information, as per his request. However, since he originally only provided these disks to me so that I could modify the drivers for my products, he omitted some files that were included with the retail versions of these packages.

Note that I have the source code for edition 27 of SFormat, but unfortunately not for edition 31.


icon to link to SDisk Level 1 User Manual file SDisk (release #2) User's Manual.
For OS-9 Level I on the CoCo 2.
(591KB .pdf scanned image)
icon to link to SDisk3 Level 2 User Manual file SDisk3 User's Manual.
For OS-9 Level II on the CoCo 3.
(85KB .pdf scanned image)
icon to link to DSK image file for SDisk edition 18 DSK image (35T/SS/DD CoCo OS-9 format) of source code and binaries for SDisk edition 18 and SFormat edition 27, and binaries for DescGen and BootFix.
(39KB .zip)
icon to link to DSK image file for SDisk edition 22 DSK image (35T/SS/DD CoCo OS-9 format) of source code and binaries for SDisk edition 22, and binaries for DescGen, BootFix, ModBuster, and SFormat edition 27.
(42KB .zip)
icon to link to DSK image file for SDisk edition 31 DSK image (40T/SS/DD CoCo OS-9 format) of source code and binaries for DiskType edition 6, source code for SDisk edition 31, and binaries for SFormat edition 31, DescGen3, and BootFix.
(25KB .zip)
icon to link to DSK image file for SDisk3 edition 12 DSK image (35T/SS/DD CoCo OS-9 format) of source code and binaries for SDisk3 edition 12 and DescGenL2 edition 2, and binaries for ModBuster, DiskType edition 6, FLS, Install, and SFormat edition 31.
(32KB .zip)

"FLEX" was a trademark of Technical System Consultants (TSC).
"OS-9" is a registered trademark of Microware LP.
"Radio Shack" and "Color Computer" are trademarks of Tandy Corp.
"MS-DOS" is a trademark of Microsoft Corp.
"CP/M" was a trademark of Digital Research Inc.

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Last revised 2022-May-20 11:35 PDT.
Copyright 2018-2022 David C. Wiens.


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