TRS-80 Model 12 versus 16B

The Model 16 was introduced in 1982 and was an upgraded Model II with the addition of an MC68000 subsystem that allowed you to run 16bit OSes, like TRSDOS-16, CPM-68K and TRSXENIX 1.x. On all Tandy 68K machines and operating systems the z80 ran in concert with the 68k. The z80 handled all I/O as the 68k subsystem did not have direct access to any I/O ports. The 2 CPUs would talk through shared memory and interrupts. The Model 16 also had the first appearance of the TM-848 thin line drives, white case and superior green screen CRT. The Model 12 was introduced in 1983 as the next version of the Model II. It was considered the base Tandy business system. The case dimensions were somewhat larger than the previous II/16. It had a simplified architecture in that the entire Z80 system was now on a single main board instead of the 4 separate cards of the Model II. A base Model 12 has a lot of empty space inside as it was meant to be optionally upgraded with the card cage if you needed a hard drive or 68K functionality. It also had the new lower profile keyboard with reverse gender connector compared to the II/16. The 16B released around 1984 is essentially a factory upgraded Model 12 with the card cage and the 6Mhz MC68000 subsystem consisting of a CPU card and 1 or more 16 bit memory cards. The 16B for a time was the best selling Unix workstation in the world. The 6000 released in 1985 was a slightly enhanced 16B with the biggest difference being the upgrade to an 8Mhz MC68000. This system allowed you to run XENIX 3.x and address up to 1MB of RAM.