UniFLEX
| Company / developer | Technical Systems Consultants (TSC) |
|---|---|
| Programmed in | Assembly language |
| OS family | Unix-like |
| Working state | Historic |
| Initial release | ? |
| Available language(s) | English |
| Supported platforms | Motorola 6809 family |
UniFLEX is a Unix-like operating system developed by Technical Systems Consultants (TSC) for the Motorola 6809 family which allowed multitasking and multiprocessing. It was released for DMA-capable 8" floppy, extended memory addressing hardware (software controlled 4KiB paging), Motorola 6809 based computers. Examples included machines from SWTPC and GIMIX. On SWTPC machines, UniFLEX also supported a 20 MB, 14" hard drive (OEM'd from Century Data Systems) in 1979. Later on, it also supported larger 14" drives (up to 80 MB), 8" hard drives, and 5-1/4" floppies.
Due to hardware limitations, main memory space for the UniFLEX kernel had to be smaller than 56 kB (code + data). This was achieved by writing the kernel entirely in assembly language, and by removing a few classic Unix features, such as group permissions for files. Otherwise, UniFLEX was very similar to Unix Version 7, though some command names were slightly different. There was no technical reason for the renaming. By simply restoring the Unix style names, a considerable degree of "Unix Look & Feel" could be established, though due to memory limitations the command line interpreter (shell) was less capable than the Bourne Shell known from Unix Version 7.
TSC never bundled a C compiler with UniFLEX for the 6809, though they produced one. But in the early 1980s a C language implementation became available as a 3rd party product (the "McCosh Compiler"). Using such a C compiler could establish source-level compatibility with Unix Version 7, i.e., a number of Unix tools and applications could be ported to UniFLEX - if size allowed: Unix on a PDP-11 limited executables to 64 kB of code and another 64 kB of data, while the UniFLEX limitation was approximately 56 kB for both, code and data together.
In the mid 1980s a successor version for the Motorola 68000 was announced. Though it removed the pressing space limitations, it was not commercially successful because it had to compete with source-code ports of original Unix.
The source code for UniFLEX and supporting software is available on the Internet. (The Missing 6809 UniFLEX Archive)
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