ard(a)p850ug1.demon.co.uk (Tony Duell) wrote: They started with the HP-35. All the first-generation HP handheld calculators (and the HP-46, HP-81 desktops, the HP 3380A integrator, the HP 1722A oscilliscope, and likely others) use the same chipset. the processor consists of two chips, the A&R (Arithmetic and Registers) and the C&T (Control and Timing). The calculators contained other chips, including a clock driver, ROMs, display drivers, and in higher-end models, RAM. Some of the first-generation calculators such as the HP-65 and HP-80 used multichip modules. In the second-generation calculators, starting with the HP-21 and including the HP-67, the processor was a single chip called ARC (Arithmetic, Registers, and Control). All subsequent HP calculators have used single chip microprocessors. Until 1984 they were all derived from the HP-35 architecture with various enhancements. All HP calculators introduced between 1984 and 1998, and the HP 39G, HP 40G, and HP 49G use variations of the Saturn processor.