The TI-74's architecture is descended from the never-released TI CC-40 Plus. TI utilized the CC-40 Plus ROM to create the TI-74's BIOS; it removed the CC-40's internal debugger to gain enough space to add calculator mode to the TI-74. The CC-40 Plus' cassette routines were reused in the TI-74, and the CC-40's Hexbus port underwent a physical footprint change and was renamed to Dockbus. The Hexbus protocol is 100% compatible between the CC-40 and TI-74 with an adapter.[1]
One variant, the TI-74S, has a blank faceplate instead of secondary functions to allow for customization (otherwise it is the same as the 74). Both models accepted customized ROM-modules. The TI-95, released at the same time, was a keystroke programmable descendant of the TI-59 and TI-66, with the same general form factor, but a two-line display (the second line was for function key definitions).
Technical specifications
TMS70C46 CPU[2] (C70009, another chip from TMS 7000 family also reported)[3]