Control Switches

This board handles most of the front panel switching: COMPUTE, RESET and the like. Six push buttons, two are on / off toggles (FAST and ERROR HOLD), the remainder are radio button style in that you push one in and the others metaphorically pop out. Defaults to RESET on power up. In hindsight perhaps an overly ambitious amount of circuitry to fit on one (160 x 100 mm) board (13 chips, 14 transistors and nineteen diodes!). But it works!! Despite looking like the insides of a 1970s super Jap radio.

I'll put up the actual circuit diagrams for this stuff as I go along. Just need to draw it out first...

Power Supply

Plain vanilla - the larger board produces +/- 21 volts (at 4 amps) (heat sink omitted). AC from a toroidal  transformer. The smaller board produces 6 volts. The latter is the lamp supply for the (ridiculously expensive (Swiss)) panel switches (which are using 6.3 V 1.26 W little bulbs rather than LEDs). Most of the electronics will use +/- 15 volts which will be down regulated from the +/- 21 volts locally on each board - as seems to be the fashion.

Is continuity inherently more powerful than discreteness?

Probably not. At least in practice. I imagine that the internal limitations (i.e. quantum mechanics, finite size) of our universe prevent the existence of any true analog computers, physical computation being limited to finite Turing computability [1]…

Given that everything computable is computable by a Turing machine and thus all computers are equivalent – analog (non-digital) computers are no more (less?) efficient than digital computers*. Nevertheless it’s hard to argue against analog computers having a certain cachet. And despite – or perhaps in spite of the internal limitations of our universe, and always being one for a challenge, I thought it high time I built a computer…

 *According to the Strong Church thesis (Vergis et al [2]), analogue (non-digital) computers are no more efficient than digital computers. Informally the thesis states that if some method (i.e. analogue computer) exists to carry out a calculation, then the same calculation can also be carried efficiently (that is in polynomial not exponential time) out by a Turing machine (i.e. digital computer).

[1] Eric Steinhart in The Blackwell Guide to the Philosophy of Computing and Information, p. 184, ed. Luciano Floridi, 2004.

[2] A. Vergis, K. Steiglitz, and  B. Dickinson, ‘The Complexity of Analog Computation’, Mathematics & Computers in Simulation, 28 (1986) pp. 91-113.