Choice of Logic

This document, Tech Memo #19 for the PDP-11/40 project, evaluates two potential logic technologies for the system hardware: Schottky 74S series TTL and Emitter Coupled Logic (ECL). The author concludes that for technical, cost, and product availability reasons, the 74S series TTL is the preferred choice for the majority of the processor hardware. The memo provides detailed comparisons on speed, power dissipation, cost, wiring constraints, noise immunity, and second-sourcing prospects, while also suggesting that ECL could still be utilized in specialized areas like the memory buffer for higher speed requirements.