Is agc more a microcontroller than a computer. Do they have programmer with idea of circuit (paralkel, device control etc) than “computing”
Apollo 11 Guidance Computer vs. USB-C Chargers
81–90 of 210 posts
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#82Earlier quoted context omitted.
> I doubt you could easily get things like rope core memory or just about any of the components. " Any of the components" is an exaggeration. For example, bipolar transistors are still here, here's the schematics [0] of the switched-mode power supply in the AGC - still perfectly understandable, rebuilding it can a fun weekend project. Also, discrete NOR gates are still around, although the underlying technology is di…
Fair enough. >whether the Saturn V architecture has survived We understand very well the basic approach that was taken to land on the moon and the hardware we used to do so. We'd have to re-engineer a lot of things that aren't just off-the-shelf to do it again. But we could do so pretty quickly if there were any compelling reason to do so. As I understand it, current technologies that could include moon landing are b…
> We'd have to re-engineer a lot of things that aren't just off-the-shelf to do it again.
Yes. I think this is the perspective that people trend to overlook - every engineering project is unique, in the sense that it's optimized to do the job under very specific constraints - costs, production capabilities, available materials, etc. When the circumstance changes, sometimes you simply can't just pull the same blueprint out of the archive to make another one - redesigning it is sometimes unavoidable, even if the older design is nothing wrong from a technical point-of-view. I think the same applies to software development.
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#83Whenever one of my developers tells me that my phone is too slow when their app lags on my Android 4.1 phone, I tell them the specs of Apollo 11 computer and scold them for being unable to deliver a smoothly scrolling list of messages on a freaking supercomputer in my palm.
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#84Forget AGC: Cypress CYPD4225's clock rate is higher than that of Playstation 1 (48 MHz vs 33). However, I don't see graphics specs here so there's room for growth.
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#85I find it a bit a bit scary that a microcontroller controls charger voltage. There might be a risk of power glitches or bugs causing output voltages which destroy devices.
I would say the risk is the same as with hardware 'bugs'. Where for example a passive component that drives a power transistor can exceed it's expected tolerance rate. Thats why reliable electronic systems (medical, space, avionics) have some components or circuits redundant.
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#86Earlier quoted context omitted.
I think this is the thing we'll be looking back on like this. AI in EVERYTHING. because it'll be so cheap in 20 years. Like maybe those useless automatic taps or hand dryers will finally actually know if hands are under them properly because they'll have the equivalent of a modern day supercomputer of AI power trying to figure it out.
Maybe. 20 years ago Moore's Law was in effect. We've become accustomed to "it'll be so cheap in 20 years" because, from 1947 to 2010, transistors dropped in price by a factor of two every 2 years, while getting faster starting in 1975 due to Dennard scaling. Roughly, for ten thousand transistors or so, the prices (in inflation-adjusted US dollars) and response times varied very roughly as follows: 1950: $1'048'576 (1…
GPUs, FPGAs, TPUs, etc.--combined with open source and public clouds that abstract a lot of the complexity--have helped mitigate the impact of the slowdown of CMOS process scaling especially for the workloads that really need the performance. But it's reasonable to wonder what happens when we start to run out of various "hacks" and performance stops getting cheaper and more power efficient.
Big implications that I'm not sure the tech industry fully appreciates.
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#87And despite the fact that a wall charger has more compute power than the Saturn V, we can't actually go to the moon today. We've actually lost the ability to go. No one understands how the engines on the Saturn V work anymore. It would take years to tear them apart and analyze them, and most of the original engineers are dead. And the guidance systems would have to be built back up from scratch. Kind of sad if you th…
I don't believe that's a good portrayal of the situation. I doubt that there's anything all that special about the actual Saturn V engines. Sure, maybe nobody remembers all of the engineering details about those particular engines, and it would be hard to reverse engineer them. But I'm pretty sure we would find it much easier to design and build new engines of similar spec today. SpaceX, Blue Origin, and several othe…
The F1 engine is interesting from this PoV because the thing as it is documented does not work (and even the documented design is full of weird design decisions that nobody today knows the reason for) and it worked by combination of luck and institutional knowledge of the actual machinists who built it not exactly to specifications.
In fact if you take various “high tech” designs from middle of the 20th century you will see a pattern of things that cannot work if built as designed, but work because of random effects that are certainly outside of what the original designers thought of (I have seen large amount of instrumentation electronics where voltage sag on supply voltage is part of feedback loop and it will not work without it. I highly doubt that the original engineers consciously designed that.)
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#88And despite the fact that a wall charger has more compute power than the Saturn V, we can't actually go to the moon today. We've actually lost the ability to go. No one understands how the engines on the Saturn V work anymore. It would take years to tear them apart and analyze them, and most of the original engineers are dead. And the guidance systems would have to be built back up from scratch. Kind of sad if you th…
> we can't actually go to the moon today. On the same tech we did 50 years ago.
We arguably can't go for entirely different reasons - lack of motivation.
There are things to do on the Moon, right now. Basic science ought to be enough; but applied things like material extraction and tourism would add to that. However, we consider those things lesser priority than some others - and we're getting a lot of short-term bang for our bucks, just not so much of foundation for future developments.
So, today we don't see the reason to apply efforts to get there. Those few who could justify going "in small", are to few and far between to mount a concerted effort. So we're slowly developing such things as cheap LEO launchers and lunar landers - the precursors to return to the Moon. We'll get back there - in the future, not in present. In present we still can't.
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#89Earlier quoted context omitted.
The real fun with the AGC on landing happened on Apollo 14, with a flipped bit in the abort landing flag. Percussive maintenance temporarily flipped the bit back, giving enough time for ground control to develop a hack. Didn't they just ignore the warnings on Apollo 11? And I think it was non synced timing references rather than strictly resource availability that got them on 11
The docking (like find your way back to the mothership radar) was still turned on, so the CPU was receiving the data and having to process it. The CPU was throwing an I'm overloaded signal, but dealing with it, as the process priority put docking radar as less priority than the landing sequence. So the CPU was complaining but still doing it's job. All this is from memory :P
Yes, just looked it up.
I was (partially) wrong about the un-synced frequency though. The synchro's for the docking radar ran from a different power circuit than the AGC, and whilst they were frequency locked they weren't in phase; resulting in timings getting thrown off and the priority issues.
Edit: Superb deep dive on AGC in Ars from last week https://arstechnica.com/science/2020/01/a-deep-dive-into-the...
Re: Apollo 11 Guidance Computer vs. USB-C Chargers
#90Earlier quoted context omitted.
If it can be done efficiently in asm then it can be done in C, C++, perhaps even Rust. But there are sacrifices to be made: unmaintainable “clever” code without clean abstractions.
There are architectures that are just fundamentally C-hostile. Perhaps the most famous one is 6502. No efficient way to implement stack based parameter passing, generic pointer arithmetic, and lots of other bits and pieces. You can still use C on 6502, it's just not very fast. I guess you could define another language that mostly looks like C, but built around particular CPU architecture quirks.
I wonder if you can write fast C for the 6502, though, but you'll have to constrain your use of the language considerably?