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Reverse-engineering an early calculator chip with four-phase logic - robve - 04-23-2023 03:15 PM Early integrated circuit designs are fascinating and a thing of beauty. I came across a blog article that got my attention for the amount of detail revealed in analyzing a calculator Rockwell LSI. Rockwell four-phase PMOS LSI were used in various brands of calculators in the early 70s. This article highlights the details of one such LSI. If you're a fan of early hardware and schematics like I am, this article does not disappoint! Decimal point control Look for example at this beautiful design for a decimal point decoder to display the decimal point: and its schematic: Segment driver The segment driver converts a digit to its 9 segment display output (a VFD tube): to light segments a to i (and decimal point): Transistors, resistors, capacitors and gates A lot of details are explained, such as the four-phase delay clock gate: Links Reverse-engineering an early calculator chip with four-phase logic Reverse-engineering the clock chip in the first MOS calculator Reverse-engineering the multiplication algorithm in the Intel 8086 processor Reverse-engineering the division microcode in the Intel 8086 processor The Texas Instruments TMX 1795: the (almost) first, forgotten microprocessor also features 4004, 8008, AL1, Viatron 2101, MP944 / F-14 CADC (F14 fighter flight control system), TMS 0100 calculator-on-a-chip / microcontroller - Rob