Model II Operating Systems (in chronological order)
TRSDOS Model II Version 1.1/1.2 The original Model II Z80 operating system which was released with the first Model II in 1978. Supports SSDD 8” floppy drives only. Was replaced by 2.0 fairly quickly.
TRSDOS 2.0 The second OS release for the Model II probably circa 1979. Many bug fixes and enhancements over TRSDOS 1.1/1.2 but they are completely incompatible formats. Referred to as 2.0a once 2.0b became available.
TRSDOS 2.0b Released with the Model 16 in 1982 with support for the Thinline Tandon 848 drives. Otherwise the same as 2.0a.
TRSDOS 2.0d This was an officially unreleased TRSDOS 2.0 version that supported both the SSDD Model II and the DSDD Thinline Model 12/16 drives.
TRSDOS HD There are references to TRSDOS-HD in the Model 16 documentation set but I have never seen it and not sure if it ever was released. This is in all likelihood an early name for what turned out to be TRSDOS-II 4.0.
TRSDOS-II 4.0 Completely new third Model II OS with HD support. This release actually requires a hard drive adapter because the OS requires 64k + 16K (found on the HDA). The hard drive needed to be initialized with the Hard Disk Initialization System which ran under TRSDOS 2.0.
TRSDOS-II 4.1 Introduced with the Model 16. Added support to bootstrap the new TRSDOS-16. OS could now use 16k from the 68000 memory on a Model 16 so it did not require a HDA on these machines.
TRSDOS-16 First 16 bit operating system released for the Model 16. Uses TRSDOS II 4.1 as a boot loader. Makes extensive use of TRSDOS || 4.1 under the covers. The most hybrid and hence most complicated and hence most problematic Tandy OS released.
TRSDOS-II 4.2 Introduced with the Model 12. The OS could now also use the additional 16K from the B design machine’s motherboard so it did not require a HDA on these machines. This was the first release with complete HD support and did not require the external TRSDOS 2.0 based hard drive initialization utility. There were many iterations of 4.2.x which supported different combinations of HD adapters and controllers.
TRSDOS-II 4.3 Added Arcnet support.
TRSDOS-II 4.4 Unreleased final version of TRSDOS-II
TRS-XENIX 1.x Released for the Model 16 after Tandy realized TRSDOS-16 was a flop. Licensed from Microsoft.
TRS-XENIX 3.x Released for the Model 6000. Requires the 8Mhz 68000 CPU board found in the 6000. The 6Mhz board in the 16B can be upgraded to 8Mhz according to Tech Bulletin 12/16B:044.
P&T CP/M 2.2 Pickels and Trout CP/M is considered by many to be the de-facto Model II CP/M implementation.
CP/M-68K A 68000 version of CP/M that runs on the 68K subsystem in the TRS-80 that requires any one of the z80 CP/M 2 operating systems to be installed. It is similar to TRSDOS-16 in that it uses the underlying 8-bit operating system as a boot loader and I/O system. A very interesting feature is that you can switch between z80 CPM and 68k CPM and back without losing the 68k context.
CP/M Plus Tandy badged version of CP/M 3 from DRI. It supported bank switching on the Model 12/16B/6000 so could utilize 128K of z80 memory if the machine was upgraded appropriately. See Tech Bulletin 12/16B:18.
LS-DOS 6.3.1A Compatible with the Model 4 version of LS-DOS 6.3.1. Can also utilize the optional additional z80 64K on the main logic board on the 12/16B/6000. See details below. Can be downloaded here.