First Microprocessor LSI Technology State-of-the-Art in 1968

[Microprocessor 4004]

This paper is designed to be a supplement to the paper “Architecture Of A Microprocessor” written in 1971 by Ray M. Holt. This paper is written because of the recent declassification of the 1968 F14A Central Air Data Computer (CADC) microprocessor design.

Introduction

With 30 years of computer architecture design, MOS/CMOS process technology, and computer history written in stone, it is difficult, at best, for the current readers to critically examine the architecture and technology decisions made in the time frame of 1968-69. I will attempt to set the stage with what we faced in 1968 for technology choices and I will attempt to present some of the design trade-off’s that were made that time. The architecture and logic of the F14A MOS-LSI chips were designed my Mr. Steve Geller and myself.

Of course, it is normal and natural for the current computer designer to compare all designs with the current Intel series of microprocessors. Intel has accomplished a tremendous feat in producing commercial microprocessors that have been able to meet or exceed the expectation of the computing world. However, the current accepted microprocessor definition, (i.e. the single-chip CPU) is a by-product of, mostly, Intel’s marketing needs and commercial motives and, not necessarily, the best integration of computing architecture and technology. The commercial and consumer world uses what is available at a cost-effective price.

What Did The CADC do?

The CADC performed the function of controlling the moving surfaces of the aircraft and the displaying of pilot information. The CADC received input from five main sources, 1) static pressure sensor, dynamic pressure sensor, temperature sensor, analog pilot information, and digital switch pilot information. The output of the CADC controlled the moving surfaces of the aircraft. These were the wings, maneuver flaps, and the glove vane controls. The CADC also controlled four cockpit displays for, Mach Speed, Altitude, Air Speed, and Vertical Speed. The CADC was a redundant system with real-time self-testing built-in. Any single failure from one system would switch over to the other. Two state-of-the-art quartz sensors, a 20-bit high precision analog-to-digital converter, a 20-bit high precision digital-to-analog converter, the MOS-LSI chip set, and a very efficient power unit made up the complete CADC. A team of over 25 managers, engineers, programmers, and technicians from AiResearch and American Microsystems labored for three years to accomplish a design feat never before attempted, a complete state-of-the-art, highly integrated, digital air data computer. This paper will discuss the MOS-LSI microprocessor chip set only.
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