Apollo 11 vs. USB-C Chargers (2020)

The most powerful chip in the list (Cypress CYPD4126) has 30x general purpose I/O pins.[1]

AFAIK, this is typical of USB controller chips, which generally have about 20-30 I/O pins, but I’m sure there are outliers.

The AGC seems to have four 16-bit input registers, and five 16-bit output registers[2], for a total of 144 I/O pins total.

[1] https://ta.infinity-component.com/datasheet/9c-CYPD4126-40LQ...

[2] https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#Other...

I feel like I/O would be the real pain point there. I suppose if you throw out performance you could forward X/VNC/whatever over serial (possibly with TCP/IP in the middle; SLIP is ugly but so flexible), but that's unlikely to be playable.

Yeesh. Beware the random wall wart I guess.

a universal turing machine is a particular machine which can simulate all other turing machines. the gpac, by contrast, is a family of machines: all machines built out of such-and-such a set of parts

you can't simulate an 11-integrator general-purpose analog computer or other differential analyzer with a 10-integrator differential analyzer, and you can't simulate a differential analyzer with 0.1% error on a (more typical) differential analyzer with 1% error, unless it's 100× as large (assuming the error is gaussian)

the ongoing research in the area is of course very interesting but a lot of it relies on an abstraction of the actual differential-analyzer problem in which precision is infinite and error is zero

The arithmetic circuits alone, like adders, multipliers etc., regardless if they are mechanical or electronic, analog or digital, should not be called computers.

When the arithmetic circuits, i.e. the "central arithmetical part", as called by von Neumann, are coupled with a "central control part", as called by von Neumann, i.e. with a sequencer that is connected in a feedback loop with the arithmetic part, so that the computation results can modify the sequence of computations, then this device must be named as a "computer", regardless whether the computations are done with analog circuits or with digital circuits.

What defines a computer (according to the definition already given by von Neumann, which is the right definition in my opinion) is closing the feedback loop between the arithmetic part and the control part, which raises the order of the system in comparison with a simple finite state automaton, not how those parts are implemented.

The control part must be discrete, i.e. digital, but the arithmetic part can be completely analog. Closing the feedback loop, i.e. the conditional jumps executed by the control part, can be done with analog comparators that provide the predicates tested by the conditional jumps. The state of an analog arithmetic part uses capacitors, inductors or analog integrators, instead of digital registers.

Several decades ago, I had to debug an analog computer during its installation process, before functioning for the first time. That was in a metallurgic plant, and the analog computer provided outputs that controlled the torques of a group of multi-megawatt DC electric motors. The formulae used in the analog computations were very complex, with a large number of adders, multipliers, integrators, square root circuits and so on, which combined inputs from many sensors.

That analog computer (made with op amps) performed a sequence of computations much more complex than the algorithms that were executed on an Intel 8080, which controlled various on-off execution elements of the system, like relays and hydraulic valves and the induction motors that powered some pumps.

The main reason why such analog computers have become obsolete is the difficulty of ensuring that the accuracy of their computations will not change due to aging and due to temperature variations. Making analog computers that are insensitive to aging and temperature raises their cost much above modern digital microcontrollers.