The Computer

p.37, in Whitehall, explaining the message from space:: "It's a computer program," he said quietly.; . . .; "It's in three sections. ... The first part is a design -- or rather it's a mathematical requirement which can be interpreted as a design. The second part is the program proper, the order code as we call it. The third and last part is data -- information sent for the machine to work on."
And p.39:: "Our newest computers still work in microseconds. This is a machine that must operate in milli-microseconds [10^-9s], ..."⁽¹⁾
p.54-55, Flemming telling Judy about the computer:: "The memory is in the core and the core is held in a total vacuum to within a degree or two of absolute zero."; "Each core is built up of alternating layers ... half a thou. thick ... a complete yes-no gate circuit⁽²⁾ on a spot of metal you can hardly see."; "Is that the equivalent of a brain cell?"; "If you like."; . . .; "The core's a three-metre cube. That makes several millions of millions. And there are six cores."⁽³⁾; "It's bigger than a human brain."; "Oh yes. Much bigger. And faster. And more efficient."

⁽¹⁾In the 1960s a respectable super computer, with its own building and 24-hour staff, might have a speed of 10⁶ instructions per second, as suggested, and 10⁶ bytes of main memory. Giga-hertz clock speeds (10⁹) became commonplace c2000 with, for example, the Intel(!) Pentium 3.
⁽²⁾Does that maybe sound more like a processing gate rather than just a memory bit?
⁽³⁾So let's say about 4×10¹³ brain cell equivalents. For 1961 that is a good margin over a human in terms of neuron numbers. But if the contest were in terms of synapses, it is now known to be much tighter:: There are "only" about 2×10¹⁰ neurons in a human brain. However, each neuron is connected to several thousand others on average, perhaps 10¹⁴+ synapses in total -- far higher connectivity than in electronic circuits (as of 2012). The A for A text does say "cells", that is neurons.; See Do we have brain to spare?, D. A. Drachman, Neurology 64(12) 2005 [doi] [p.med] [www]['12].