In May 1979, Tandy introduced the Model II which was first shipped in October. The Model II was not an upgrade of the Model I, but an entirely different system whose size, weight, equipment and price ($3450 for the 32 KB version) show that it was clearly intended for the small business market.
Internally, the Model II featured a passive backplane able to support up to 8 logic cards. The basic system used 4 slots, and shipped with a 12" green display, a detachable keyboard and a single Shugart single-sided, double-density 8" floppy drive that would reliably store up to 475 KB of programs and data. At that time, this was an enormous amount for personal desktop computers, compared to the 80 - 100 KB the newer 5.25 shugart drives could store.
Furthermore, the Model II had provision for plugging in an expansion chassis which allowed up to 3 more floppy drives to be added. Totalling 2 MB, this storage capacity allowed the Model II to do things that were impossible with most other systems of the time, and made it very popular for accounting systems and large database management. Tandy also offered additional chained 5 MB and 10 MB hard drives.
When the machine was launched, Tandy only supported its TRS-DOS Operating System through versions 1.1, 1.2 and 2.0. Interestingly enough, these OSs were Y2K compliant, whereas further Model III and IV OSs didn't recognise dates beyond 1987! Several languages were available: BASIC interpreter and compiler, FORTRAN IV, COBOL and PASCAL, as well as a strange but efficient word processor called Scripsit. Fortunately, several third-party developers quickly adapted the CP/M 2.2 OS which became an important part of the sales pitch, and allowed standard business programs like WordStar word processor or the new VisiCalc spreasheet to be run, along with enabling the exchange of data with other CP/M systems. Options for the machine also included a 6 MHz 68000 board with extra memory so it could run XENIX.
The Model II was on sale for four years. It was replaced in 1983 by the more advanced Mod. 12 and Mod. 16 in which a dual 5.25" 1.2 MB drive took the place of the old 8" drive. A smaller version of the Model II was also released, with an upgraded video display, and 5.25" floppies.