Reverse-engineering an early calculator chip with four-phase logic

[robve]

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