Someone opened an issue: "Check continuity on O2 cryogenic tanks before allowing stir" https://github.com/chrislgarry/Apollo-11/issues/3
ELI5?
Apollo 11 Guidance Computer source code
131–140 of 150 posts
Re: Apollo 11 Guidance Computer source code
#132Someone opened an issue: "Check continuity on O2 cryogenic tanks before allowing stir" https://github.com/chrislgarry/Apollo-11/issues/3
ELI5?
Re: Apollo 11 Guidance Computer source code
#133Someone opened an issue: "Check continuity on O2 cryogenic tanks before allowing stir" https://github.com/chrislgarry/Apollo-11/issues/3
This is a classic XY issue, suggesting a fix ("Check continuity...") instead of describing the problem ("O2 tanks exploded during Apollo 13 mission").
Further, I believe that the suggested fix is incorrect, or at least insufficient. The Apollo 13 investigation indicated that a list of factors led to the fan wires in the O2 tanks having damaged insulation. However, unless the wires were already short-circuited before stirring, checking continuity first would not have detected the short. Indeed, the tank was stirred twice earlier in the mission without incident. The investigation suggested that operating the fans itself may have eventually moved the wires into contact with each other, which combined with the damaged insulation, finally allowed an electrical arc and the resulting explosion to occur.
The correct fix is to upgrade the thermostatic switches which protect the tank heaters from overheating to accommodate 65 V DC, so that the fan wiring isn't damaged in the first place. In addition, the tank acceptance procedure should be amended to require switch cycling under load.
Source: http://history.nasa.gov/SP-4029/Apollo_13a_Summary.htm
Re: Apollo 11 Guidance Computer source code
#134Earlier quoted context omitted.
I could be wrong. But I think part of why they did it this way was so they could edit things on the fly if a emergency dictated so. Having to ship a compiler (would have likely been an entire separate computer) would have not been feasible. With things done this way and documented this why they could (fairly sure did) have the pages printed out on paper and such. And if say there was some bug or new routine that need…
> I could be wrong. But I think part of why they did it this way was so they could edit things on the fly The AGC code was stored in ROM. Notably a specific kind of ROM called "rope memory".
"The bulk of the software was on read-only rope memory and thus couldn't be changed in operation, but some key parts of the software were stored in standard read-write magnetic-core memory and could be overwritten by the astronauts using the DSKY interface, as was done on Apollo 14."
Seams you were mostly right about not being able to change it. I was only somewhat right because I assumed it would all be editable. I over estimated the technology they had back then. I would gather from that there was for more fixed code than editable.
Source: https://en.wikipedia.org/wiki/Apollo_Guidance_Computer
Re: Apollo 11 Guidance Computer source code
#135Earlier quoted context omitted.
I have one word for those: retroreflectors.
And another- telemetry
Not that I believe in any particular moon conspiracy hypothesis, but the reflectors being on the moon do not proove anything else than someone did put them there. Wether humans went on the moon to put them there, or some other delivery system was used is (strictly) logically up for debate.
Re: Apollo 11 Guidance Computer source code
#136I will now be adding this comment to all of my code: HONI SOIT QUI MAL Y PENSE
https://github.com/chrislgarry/Apollo-11/blob/master/BURN_BA...
Re: Apollo 11 Guidance Computer source code
#137Earlier quoted context omitted.
wow , wow ! Looks like I don't understand the first thing about the CPU design . Do CPUs have to be designed to IDLE ? Can you throw some more light on this ?
A basic model of a CPU is running an infinite loop like this: 1. If interrupts not masked, check for interrupt 2. Load instruction 3. Advance instruction pointer 4. Execute instruction It doesn't ever stop - as soon as the current instruction is finished executing it moves on to the next one. So, if you don't have anything better for the CPU to do, you need to have it spin in a loop of instructions anyway. More moder…
Why do CPUs and GPUs run hotter when doing more intensive tasks?
In your last statement I could see it making sense where the CPU actually halts, but did prior CPUs always run at about the same temperature? Or do these idle processes throw fewer instructions at one time so it's not as overwhelmed?
Re: Apollo 11 Guidance Computer source code
#138I will now be adding this comment to all of my code: HONI SOIT QUI MAL Y PENSE https://github.com/chrislgarry/Apollo-11/blob/master/BURN_BA...
"Shame on him who thinks ill of it." It's almost as if the authors anticipated the need to administer percussive therapy, Buzz Aldrin style, to trolls of the far-distant future.
Re: Apollo 11 Guidance Computer source code
#139Earlier quoted context omitted.
A basic model of a CPU is running an infinite loop like this: 1. If interrupts not masked, check for interrupt 2. Load instruction 3. Advance instruction pointer 4. Execute instruction It doesn't ever stop - as soon as the current instruction is finished executing it moves on to the next one. So, if you don't have anything better for the CPU to do, you need to have it spin in a loop of instructions anyway. More moder…
Why do CPUs and GPUs run hotter when doing more intensive tasks? In your last statement I could see it making sense where the CPU actually halts, but did prior CPUs always run at about the same temperature? Or do these idle processes throw fewer instructions at one time so it's not as overwhelmed?
> did prior CPUs always run at about the same temperature?
Basically, yes. But then they typically produced so little heat they had passive heatsinks, up to and including the Pentium II (~20 W TDP) and ATI Rage 128 that I used back in '99.
Re: Apollo 11 Guidance Computer source code
#140Earlier quoted context omitted.
A basic model of a CPU is running an infinite loop like this: 1. If interrupts not masked, check for interrupt 2. Load instruction 3. Advance instruction pointer 4. Execute instruction It doesn't ever stop - as soon as the current instruction is finished executing it moves on to the next one. So, if you don't have anything better for the CPU to do, you need to have it spin in a loop of instructions anyway. More moder…
Why do CPUs and GPUs run hotter when doing more intensive tasks? In your last statement I could see it making sense where the CPU actually halts, but did prior CPUs always run at about the same temperature? Or do these idle processes throw fewer instructions at one time so it's not as overwhelmed?
Modern CPUs, GPUs and SOCs have power management states that disable entire submodules when they're not in use, by actually gating off the clock to them. If you run without power management enabled, you'll find that they run hot all the time.