The Manchester machines were very significant for at least two reasons. First off, they were the first to feature "Williams tube" CRT memory, which was the hig

The Manchester machines were very significant for at least two reasons. First off, they were the first to feature "Williams tube" CRT memory, which was the high-speed memory of choice in any early computer effort that could afford it (including the IAS machine which is Dyson's subject, and for which he apparently fails to give Williams proper credit). Second, it was the first machine to feature any kind of an index register, a facility that was quite widely copied. You can trace the influence from the spread of the Manchester name for the facility: they called it the "B-tube", a reference to the internal structure of their own machine. (Already having an "A-tube" for the accumulator, and a "C-tube" for control registers, they used the first free letter.) And if you read through the computing literature of the '50s, you'll find frequent references to index registers using terms like "B-boxes", which are otherwise inexplicable.