VideoGist - Building the BBC Micro (The Beeb)

Building the BBC Micro (The Beeb) - Computerphile

Computerphile

12 min, 26 sec

The video outlines the challenges and processes involved in developing the BBC Microcomputer, from initial sketches to final production.

Summary

The BBC Micro was developed under a tight deadline without a working prototype initially, relying on paper sketches.
The project was a part-time venture fueled by an exchange of designs for parts, which eventually led to an intensive prototyping week.
The transition from Acorn's Atom to the BBC Micro was driven by the BBC's educational programming needs and the emerging 16-bit technology.
The machine's design was pulled off the drawing board to meet the BBC's cost point, leading to a dual processor system that was simplified to a single processor with the option of a secondary one.
The BBC Micro's features and hardware specifications were shaped by a constructive dialogue between the BBC and Acorn.

Chapter 1

Initial Development Phase

0:00 - 39 sec

The beginning stages of the BBC Micro's development involved a rushed request from the BBC and reliance on mere paper sketches without detailed plans.

Herman rang around to announce the BBC's visit for a prototype, which was not yet built.
Roger's skepticism was met with determination by the team to create a working prototype.
The project started as a part-time, in-kind contribution where designs were exchanged for parts.

Chapter 2

Prototyping Under Pressure

0:39 - 2 min, 38 sec

A prototype for the BBC Micro had to be developed rapidly, culminating in an intense three-day work period.

The BBC's interest in a machine for their educational program triggered the prototyping of the BBC Micro.
The design was based on the Acorn Atom's successor, internally known as the Proton, which was to transition from 8-bit to 16-bit.
Due to the BBC's cost constraints, the design shifted from a dual processor system to a single main processor with optional secondary processing.

Chapter 3

Collaboration with the BBC

3:17 - 2 min, 36 sec

The BBC's involvement brought specific requirements and collaborations, impacting the machine's features and programming language.

The BBC's research department had a major educational focus and required a machine that could illustrate programming concepts on their show.
BBC Basic emerged as a compromise between Acorn's past experience and the BBC's demands for a cleaner language.
Hardware features like teletext mode and speech generation chips were added to meet BBC specifications.

Chapter 4

Finalizing the Design

5:53 - 3 min, 37 sec

Final design decisions included technological advancements and negotiations with the BBC on aspects like power supplies.

The BBC initially rejected switch mode power supplies due to radio frequency interference, leading to overheating issues with linear power supplies.
Other design features included a single block of shared memory and ULA technology to integrate systems.
The memory system was aggressively designed to operate at 4 megahertz, pushing the limits of available technology at the time.

Chapter 5

Production Challenges and Legacy

9:30 - 2 min, 52 sec

Production faced challenges with memory addressing and bus capacitance, but the BBC Micro became known for its reliability.

The data bus was overloaded, requiring unconventional solutions like a resistor pack to simulate an engineer's finger.
Despite the aggressive design and minimal margins for error, the BBC Micro was surprisingly reliable.
The machine's durability is reflected in the longevity of its components, except for the power supply capacitors.