Apollo 11 Guidance Computer vs. USB-C Chargers

Post by _0w8t » Sat, Feb 08, 2020, 9:19 PM UTC

vardump wrote: post #59

TazeTSchnitzel wrote: post #29

Earlier 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.

Post by HocusLocus » Sun, Feb 09, 2020, 1:22 AM UTC

garaetjjte wrote: post #202

xp84 wrote: post #114

I'd like to also see an article examining these computing power attributes on the piece of garbage embedded computer on the front of the gas pumps where the lag between registering every keypress is like 800ms, and every screen redraw takes about 2000ms. It takes me an extra 60 seconds to get gas now thanks to how slow these things are, and it is nearly universal despite whether they appear to be 20 year old or new d…

>I bet they run Java. And maybe it runs on Windows CE device with anemic CPU.. On aside.. fuel pumps with embedded computers and payment terminals are US thing? There it is necessary to pay at the cashier after filling. (and it is most annoying part, because they try to upsell you hotdog/coffee, washer fluid and encourage to join loyalty program)

Post by int_19h » Sun, Feb 09, 2020, 5:10 AM UTC

Tuna-Fish wrote: post #186

int_19h wrote: post #125

Earlier quoted context omitted.

Given that all that high-level control flow is rewritten into gotos anyway, why would that make a difference in general, or specifically for 6502?

All high-level control flow is very definitely not rewritten into gotos. Almost all cpus have some form of function call instruction, and c functions are implemented by using it. Without such an instruction, or even a fast way to model it, C becomes much less efficient to implement.

Post by takeda » Sun, Feb 09, 2020, 5:55 AM UTC

stevenjgarner wrote: post #193

xp84 wrote: post #114

I'd like to also see an article examining these computing power attributes on the piece of garbage embedded computer on the front of the gas pumps where the lag between registering every keypress is like 800ms, and every screen redraw takes about 2000ms. It takes me an extra 60 seconds to get gas now thanks to how slow these things are, and it is nearly universal despite whether they appear to be 20 year old or new d…

I wonder if any of that performance is due to the intrinsic safety requirements, especially the need to select only intrinsically safe components that will never produce enough energy to ignite gasoline vapors under any transient condition - https://en.wikipedia.org/wiki/Intrinsic_safety

Post by lopmotr » Sun, Feb 09, 2020, 8:51 PM UTC

sterlind wrote: post #69

lopmotr wrote: post #46

Earlier quoted context omitted.

Something requiring human labor doesn't make it impossible! There's no lost scientific knowledge. Engineering details may be lost but we can design a new rocket that works just as well. We send unmanned probes to the moon all the time. There's no loss of resources to do it either. We have more money than ever before. We just can't be bothered. That's all.

Even if we could be bothered, I think we've lost the political technology to organize large government projects and complete them on a sane budget/timetable. The budget plan for the James Webb Space Telescope was $500m with completion in 2007. We're now at $9.6b with completion predicted in 2021. Some of the cost overruns and delays were caused by the unexpected complexity of fabricating the mirrors and assembling th…