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Apollo 11 vs. USB-C Chargers (2020)

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

#61

Post by Tommstein »

coder543 wrote: post #47
hinkley wrote: post #38

Earlier quoted context omitted.

Analog computers have to be rebuilt if it turns out the program is wrong though, don’t they?

In the context of this thread, I believe even a digital computer would have to be rebuilt if the program is wrong... :P Unless you typically salvage digital computers from the wreckage of a failed rocket test and stick it in the next prototype. If the FCC is wrong, kaboom.

Presumably they meant a program being discovered to be wrong before the computer was actually launched. And meant literally building a whole new computer, not just recompiling a program.

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

#62

Post by [deleted] »

scaredginger wrote: post #60
coder543 wrote: post #47

Earlier quoted context omitted.

In the context of this thread, I believe even a digital computer would have to be rebuilt if the program is wrong... :P Unless you typically salvage digital computers from the wreckage of a failed rocket test and stick it in the next prototype. If the FCC is wrong, kaboom.

I'm pretty sure you can perform tests and find defects without actually flying the rocket

[deleted]

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

#63

Post by kens »

jcalvinowens wrote: post #51

>> others point out that the LVDC actually contains triply-redundant logic. The logic gives 3 answers and the voting mechanism picks the winner. This is a very minor point... but three of something isn't triple redundancy: it's double redundancy. Two is single redundancy, one is no redundancy. Unless the voting mechanism can somehow produce a correct answer from differing answers from all three implementations of the…

The official name for the LVDC's logic is triple modular redundant (TMR). The voting mechanism simply picks the majority, so it can tolerate one failure. The LVDC is a serial computer, which makes voting simpler to implement, since you're only dealing with one bit at a time.

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

#64

Post by KRAKRISMOTT »

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.

You forgot the most important one, the human computers at ground control.

Who said women can't do math?

https://www.smithsonianmag.com/science-nature/history-human-...

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

#65

Post by hinkley »

Tommstein wrote: post #61
coder543 wrote: post #47

Earlier quoted context omitted.

In the context of this thread, I believe even a digital computer would have to be rebuilt if the program is wrong... :P Unless you typically salvage digital computers from the wreckage of a failed rocket test and stick it in the next prototype. If the FCC is wrong, kaboom.

Presumably they meant a program being discovered to be wrong before the computer was actually launched. And meant literally building a whole new computer, not just recompiling a program.

Yeah, though to be fair, some of the programs Apollo ran were on hand woven ROMs, so I may be making too fine a distinction. The program itself was built, not compiled. It if we are comparing with today, it would just be installed, not constructed.

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

#66

Post by hinkley »

lmm wrote: post #54
hinkley wrote: post #37

Earlier quoted context omitted.

I still want to see postgres or sqlite running straight on a storage controller some day. They probably don’t have enough memory to do it well though.

Booting Linux on a hard drive was what, 15 years ago now?

Have you ever tried to google that?

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

#67

Post by mulmen »

KRAKRISMOTT wrote: post #64
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.

You forgot the most important one, the human computers at ground control. Who said women can't do math? https://www.smithsonianmag.com/science-nature/history-human-...

> Who said women can't do math?

The straw man?

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

#68

Post by adastra22 »

p-e-w wrote: post #36
jojobas wrote: post #21

Earlier quoted context omitted.

That sounds way too low. Modern fly-by-wire planes are said to have 12-way voting.

I don't understand this. If two or more computers fail in the same way simultaneously, isn't it much more likely that there is a systemic design problem/bug rather than some random error? But if there is a design problem, how does having more systems voting help?

They are not going to fail the same way simultaneously. This is protecting against cosmic ray induced signal errors within the logic elements, not logic errors due to bad software.

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

#69

Post by Shawnj2 »

AnotherGoodName wrote: post #10

Pretty much all USB chips have a fully programmable CPU when you go into the data sheets. It feels silly for simple hid or charging devices but basic microcontrollers are cheap and actually save costs compared to asics.

Where I work they were considering using an FPGA over an MCU for a certain task but decided against it because the FPGA couldn’t reach the same low power level as the MCU

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

#70

Post by jojobas »

p-e-w wrote: post #36
jojobas wrote: post #21

Earlier quoted context omitted.

That sounds way too low. Modern fly-by-wire planes are said to have 12-way voting.

I don't understand this. If two or more computers fail in the same way simultaneously, isn't it much more likely that there is a systemic design problem/bug rather than some random error? But if there is a design problem, how does having more systems voting help?

Which is why different sets of computers will run software developed by independent groups on different principles, so that they very unlikely to fail simultaneously.
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