Designing a Microprocessor from Scratch 2014-05-26

Introduction

A long time ago, before integrated microprocessors, there was a wonderful chip with a number designation of 74181 (a 4-bit ALU). This was a time when you made up a microprocessor using many TTL logic chips. Two or four of these ALU chips made the core of a microprocessor. For a 16-bit ALU, there was a companion chip designated 74182 which was used to speed up the carry output.


These chips are no longer readily available but the published circuit diagram makes it useful...

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