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Apollo 11 vs. USB-C Chargers (2020)

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Re: Apollo 11 vs. USB-C Chargers (2020)

#131

Post by adrian_b »

kens wrote: post #128
adrian_b wrote: post #124

Earlier quoted context omitted.

Most "analog computers" have been simple, and even if they usually provided the solution of a system of ordinary differential equations, that does not require a control part, making them no more closer to a complete computer than a music box that performs a fixed sequence. I agree that this kind of "analog computers" does not deserve the name of "computer", because they are equivalent only with the "registers + ALU"…

You're describing a "hybrid computer". These were introduced in the late 1950s, combining a digital processor with analog computing units. I don't understand why you and kragen want to redefine standard terms; this seems like a pointless linguistic exercise.

"Hybrid computer" cannot be considered as a standard term, because it has been used ambiguously in the past.

Sometimes it has been applied to the kind of computers mentioned by me, with a digital control part and a completely analog arithmetic part.

However it has also been frequently used to describe what were hybrid arithmetic parts, e.g. which included both digital registers and digital adders and an analog section, for instance with analog integrators, which was used to implement signal processing filters or solving differential equations.

IMO, "hybrid computer" is appropriate only in the second sense, for hybrid arithmetic parts.

The control part of a CPU can be based only on a finite state automaton, so there is no need for any term to communicate this.

On the other hand, the arithmetic part can be digital, analog or hybrid, so it is useful to speak about digital computers, analog computers and hybrid computers, based on that.

Re: Apollo 11 vs. USB-C Chargers (2020)

#132

Post by ReptileMan »

The great thing about the AI age is that we are once again performance constrained so people start to rediscover the lost art of actually optimizing a program or runtime (the last such age were the waning days of ps2. Those guys made GoW 2 run on 32 megs of ram ... respect)

Re: Apollo 11 vs. USB-C Chargers (2020)

#133

Post by fuzzfactor »

ssgodderidge wrote: post #29

> The Anker PowerPort Atom PD 2 USB-C Wall Charger CPU is 563 times faster than the Apollo 11 Guidance Computer Wild to think the thing that charges my devices could be programmed to put a human on the moon

The proven way to fly people to the moon and back using such low-powered computers was to have a supporting cast of thousands who were naturally well qualified using their personal slide rules to smoothly accomplish things that many of today's engineers would stumble over using their personal computers.

Plenty of engineers on the ground had no computers, and the privileged ones who did had mainframes, not personal at all.

A computer was too valuable to be employed doing anything that didn't absolutely need a computer, most useful for precision or speed of calculation.

But look what happens when you give something like a mainframe to somebody who is naturally good at aerospace when using a slide rule to begin with.

Re: Apollo 11 vs. USB-C Chargers (2020)

#134

Post by ThePowerOfFuet »

gumby wrote: post #127
thebestmoshe wrote: post #19

Earlier quoted context omitted.

Isn’t this basically what SpaceX is doing? > The flight software is written in C/C++ and runs in the x86 environment. For each calculation/decision, the "flight string" compares the results from both cores. If there is a inconsistency, the string is bad and doesn't send any commands. If both cores return the same response, the string sends the command to the various microcontrollers on the rocket that control things…

Seems risky. I remember the automated train control system for the Vienna Hauptbahnhof (main train station) had an x86 and a SPARC, one programmed in a procedural language and one in a production language. The idea was to make it hard to have the same bug in both systems (which could lead to a false positive in the voting mechanism).

This is a great technique to avoid common-mode failures.

Re: Apollo 11 vs. USB-C Chargers (2020)

#135

Post by milkey_mouse »

kragen wrote: post #92
kens wrote: post #16

> Apollo 11 spacecraft contains 4 computers Analog computers don't get the respect they deserve. There's one more computer, the FCC. The Flight Control Computer is an analog computer in the Saturn V that controlled the rocket gimbals. It's a two-foot cylinder weighing almost 100 pounds.

i think it's (unintentionally) misleading to describe analog 'computers' as 'computers'. what distinguishes digital computers from other digital hardware is that they're turing-complete (if given access to enough memory), and there isn't any similar notion in the analog domain the only reason they have the same name is that they were both originally built to replace people cranking out calculations on mechanical desk…

https://www.gleech.org/first-computers

Re: Apollo 11 vs. USB-C Chargers (2020)

#136

Post by blauditore »

I'm a bit tired of all the sensationalist "look what landed on the moon vs. today's hardware" comparisons. The first airplanes didn't have any sort of computer on board, so computation power is not the single deciding factor on the performance and success of such an endeavor.

The software (and hardware) of the Apollo missions was very well-engineered. We all know computation became ridiculously more powerful in the meantime, but that wouldn't make it easy to do the same nowadays. More performance doesn't render the need for good engineering obsolete (even though some seem to heavily lean on that premise).

Re: Apollo 11 vs. USB-C Chargers (2020)

#137

Post by midasuni »

eesmith wrote: post #120
kragen wrote: post #92

Earlier quoted context omitted.

i think it's (unintentionally) misleading to describe analog 'computers' as 'computers'. what distinguishes digital computers from other digital hardware is that they're turing-complete (if given access to enough memory), and there isn't any similar notion in the analog domain the only reason they have the same name is that they were both originally built to replace people cranking out calculations on mechanical desk…

What do you regard as the first digital, Turing-complete (if given enough memory) computer? ENIAC, for example, was not a stored-program computer. Reprogramming required rewiring the machine. On the other hand, by clever use of arithmetic calculations, https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.37.... says the Z3 could perform as a Universal Computer, even though, quoting its Wikipedia page, "because it…

Colossus was before eniac, but was also programmed by plugging up. Baby was a stored program machine and had branching

Re: Apollo 11 vs. USB-C Chargers (2020)

#138

Post by theon144 »

somat wrote: post #98

The ariicle was a lot of fun however I felt it missed a important aspect about the respective computers. IO channels. I don't know about the USB charge controllers. But the AGC as a flight computer had a bunch of inputs and outputs. Does a Richtek RT7205 have enough IO?

I have no clue as to the I/O requirements of the AGC, but I imagine that with ~500x the performance, a simple I/O expander could fill the gap?

Re: Apollo 11 vs. USB-C Chargers (2020)

#139

Post by creatonez »

kens wrote: post #16

> Apollo 11 spacecraft contains 4 computers Analog computers don't get the respect they deserve. There's one more computer, the FCC. The Flight Control Computer is an analog computer in the Saturn V that controlled the rocket gimbals. It's a two-foot cylinder weighing almost 100 pounds.

Some info about the Flight Control Computer:

> The Flight Control Computer (FCC) was an entirely analog signal processing device, using relays controlled by the Saturn V Switch Selector Unit to manage internal redundancy and filter bank selection. The FCC contained multiple redundant signal processing paths in a triplex configuration that could switch to a standby channel in the event of a primary channel comparison failure. The flight control computer implemented basic proportional-derivative feedback for thrust vector control during powered flight, and also contained phase plane logic for control of the S-IVB auxiliary propulsion system (APS).

> For powered flight, the FCC implemented the control law $ \beta_c = a_0 H_0(s) \theta_e + a_1 H_1(s) \dot{\theta} $ where $ a_0 $ and $ a_1 $ are the proportional and derivative gains, and $ H_0(s) $ are the continuous-time transfer functions of the attitude and attitude rate channel structural bending filters, respectively. In the Saturn V configuration, the gains $ a_0 $ and $ a_1 $ were not scheduled; a discrete gain switch occurred. The Saturn V FCC also implemented an electronic thrust vector cant functionality using a ramp generator that vectored the S-IC engines outboard approximately 2 degrees beginning at 20 seconds following liftoff, in order to mitigate thrust vector misalignment sensitivity.

https://ntrs.nasa.gov/api/citations/20200002830/downloads/20...

Re: Apollo 11 vs. USB-C Chargers (2020)

#140

Post by kqr »

ThePowerOfFuet wrote: post #134
gumby wrote: post #127

Earlier quoted context omitted.

Seems risky. I remember the automated train control system for the Vienna Hauptbahnhof (main train station) had an x86 and a SPARC, one programmed in a procedural language and one in a production language. The idea was to make it hard to have the same bug in both systems (which could lead to a false positive in the voting mechanism).

This is a great technique to avoid common-mode failures.

Do you have data to back that claim up? I remember reading evidence to the contrary, namely that programmers working on the same problem -- even in different environments -- tend to produce roughly the same set of bugs.

The conclusion of that study was that parallel development mainly accomplishes a false sense of security, and most of the additional reliability in those projects came from other sound engineering techniques. But I have lost the reference, so I don't know how much credibility to lend my memory.

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