Sardis Technologies
OF-Link (FLEX under OS-9)

OF-Link allows one (or more) instances of the TSC 6809 FLEX operating system to run under OS-9/6809 Level II (or NitrOS-9/6809 or 6309 Level 2) on the Radio Shack Color Computer 3 (CoCo 3), or in a CoCo 3 emulator such as VCC.

OF-Link is an OS-9 module that acts as an interface between the FLEX and OS-9 operating systems. An actual copy of the FLEX operating system runs concurrently with, and as a process of, the (Nitr)OS-9 operating system, but OF-Link translates all FLEX disk and console and printer I/O calls to OS-9 system calls. (This is a different method than how the Wine compatibility layer lets Microsoft Windows applications run on Linux, because Wine doesn't use actual Windows operating system code.)

OF-Link allows you to run many of your existing FLEX programs under (Nitr)OS-9 without requiring you to obtain OS-9 versions of them. This is especially useful where a program was only available in a FLEX version.

OF-Link features:

OF-Link was first advertised in RAINBOW magazine in the September 1988 issue. It was enthusiastically reviewed on pages 16-17 in the April 1989 issue of '68' Micro Journal. The review had a few minor errors, and subsequent updates eliminated some reported problems:

Only version 0.5 was developed and distributed. Sales of OF-Link were so few that I couldn't afford to spend the time required to finish implementing the planned enhancements to create version 1.0. OF-Link was an interesting and useful product, but a marketing and financial flop.

GIMIX O-FLEX from GMX was a similar software package that ran under OS-9 GMX II and GMX III versions of OS-9/6809 Level II on SS-50 bus computers. TSC also produced a version of FLEX that ran under the UniFLEX/6809 operating system.

Unfortunately, the format of the FLEX virtual disk images (contained in OS-9 files) used by OF-Link is unique to OF-Link and is not supported by any other software except for my UFDR program, which runs under Windows. FLEX DSK image files can be opened by the VCC CoCo 3 emulator (also running under Windows) as emulated physical disks. Linux users can't run either of these programs (except maybe under Wine?). OF-Link running on real CoCo 3 hardware can use the CoCo SDC floppy disk emulator to open FLEX DSK image files, but CoCo SDC doesn't support many of the common FLEX disk configurations. This makes it difficult at the moment for non-Windows users to get files from FLEX DSK images for use with OF-Link.

When you read the two manuals shown below, display them at a large size. The Letter Gothic font I used makes it very hard to distinguish between a period and a comma when displayed at a reduced size. If anyone knows of a better version of this font, please let me know. (I found the similar Financial font which is better, but not perfect, either.) The Letter Gothic font that was printed on daisywheel printers in the 1980's was much better.

icon to link to Of-Link User Manual file OF-Link User's Manual.
(383KB .pdf)
icon to link to OF-Link Addtional Notes file OF-Link Additional Notes.
(172KB .pdf)
icon to link to DSK image file of original OF-Link distribution disk DSK image (35T/SS/DD CoCo OS-9 format) of original OF-Link distribution disk.
(11KB .zip)
icon to link to DSK image of ready to boot RTR version of OF-Link DSK image (40T/SS/DD CoCo OS-9 format) of RTR version of OF-Link that is ready to boot NitrOS-9 and FLEX, with instructions.
(90KB .zip)
icon to link to DSK image file with source code for OF-Link and related programs DSK image (35T/SS/DD CoCo OS-9 format) of OS-9 source code for OF-Link and related programs.
(FLEX source code not available yet)
(33KB .zip)

FLEX and SK*DOS

Programs that run under FLEX can be downloaded from various sites such as here and here. Archived issues of '68' Micro Journal have much useful information on FLEX and programs for FLEX. Several FLEX manuals can be downloaded, and you can read about the history of FLEX. You can find source code for FLEX, such as a well commented disassembly (see files FLEX.TXT and FLEXFMS.TXT in flex_srces.dsk), and even the genuine commented original TSC source code for version 3.02 (see files "dos" and "fms" in the FLEX-4-UniFLEX archive).

Peter Stark developed an operating system called SK*DOS (originally called STAR-DOS) that was mostly compatible with FLEX, and also works with OF-Link:  [1] [2] [3] [4] [5]

Ready To Run

Since the TSC FLEX operating system may now be freely distributed, as may the NitrOS-9 operating system, and also the SDisk3 floppy disk driver, I am now able to supply a Ready To Run (RTR) disk image (see above). This is much easier to use than the software on my original distribution disk which required many installation steps. The RTR disk is bootable and ready to run, and includes the SDisk3 driver pre-installed in the NitrOS-9 OS9Boot file, a shell procedure file that calls a pre-configured version of OF-Link, and a FLEX virtual disk containing the linked FLEX v3.01 operating system and related utilities. This RTR image runs just fine on the VCC CoCo 3 emulator (I tested it on versions 2.0.1b and 2.1.0.5). One user has reported successfully running the RTR image on a real CoCo 3, although he used a CoCo SDC instead of real floppies.

Source Code

The source code files for the OS-9 components of OF-Link are finally available!! -- refer to link above. This took a while because I haven't yet found all of my floppy disks containing these files. I did find the paper assembler listing for the OF_Link module, but it is marked up with lots of modifications that are incomplete and probably not runnable -- I had started working on version 1.0 but never finished it. I knew it would be a lot of work to type it all in again from the printout.

But in July 2025 I did re-type the OS-9 source code for the OF_Link module -- all 52 pages of it! This wasn't easy, since there were three sets of markups on it: first set in pencil, second set in blue ink, third set in red ink. Some of the markups obliterated the original code, so I had to use some detective work to determine what it had been for version 0.5 as distributed. But after four days of work I had re-created two versions of the source code such that the assembler can create an OF_Link module which:

It took another two days for me to clean up the comments and formatting before creating the disk image containing the source code files.

However, the source code files for several of the related FLEX utility programs were also on floppy disks I haven't yet found, so it will be a while before I re-type these files and make them available.

Version 2.0

Hopefully someday I will find the time to create OF-Link version 2.0, that will contain these improvements:


"FLEX" was a trademark of Technical System Consultants (TSC).
"6809 FLEX Plus 10" is a trademark of David C. Wiens, dba Sardis Technologies.
"SK*DOS" is a registered trademark of Star-K Software Systems Corp.
"OS-9" is a registered trademark of Microware LP.
"Radio Shack" and "Color Computer" are trademarks of Tandy Corp.

Last revised 2025-Jul-07 17:57 PDT.
Copyright 2018- David C. Wiens.

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