wjc@llex.ll.mit.edu ( Bill Chiarchiaro) (06/07/91)
In light of machines such as the HP48SX which have a couple of hundred kilobytes of firmware, I thought it might be interesting to see how much firmware was in some of the older HP calculators. HP used to publish something called "The Hewlett-Packard Personal Calculator Digest." It was basically an annual calculator catalog, but it did have some worthwhile articles. Volume Three, 1977, had an article called "Microcode: Electronic Building Blocks For Calculators." It was explained that the HP-35 used three ROMs, each of which held one "page." A page was 256 10-bit words. While the HP-45 was under development, a "quad" ROM was produced which could hold four pages. The HP-45 was going to need 6 of the old ROMS; with two quad ROMS, there were two pages left over. It was in those two extra pages that the HP-45 clock was coded. The article showed what looked like the body of an HP-19C cabled to a box that contained several 20-odd-pin DIP EPROMs, some other ICs, and an AC power supply. Apparently, this was an emulator used for debugging and quality checking of firmware under development. Presumambly, similar setups existed for other calculator models. Also, the Digest article and several HP Journal articles indicate that essentially the same processor architecture was used from the HP-35 through at least the HP-19C/HP-29C. The Digest article contained the following table showing the number of firmware quads in various models: HP-80: 2 HP-22: 2 HP-65: 3 HP-91: 3 HP-70: 2 HP-29C: 4 HP-55: 3 HP-27: 3 HP-19C: 5 HP-25C: 2 HP-10: 1.5 HP-67: 5 HP-21: 1 HP-97: 6 HP-25: 2 HP-92: 6 The 1.5 quads for the HP-10 is not a typo; that's what the article showed. Bill Chiarchiaro wjc@ll.mit.edu