Linked by Thom Holwerda on Sun 12th Aug 2012 22:16 UTC
General Development "I cannot help but speculate on how the software on the Curiosity rover has been constructed. We know that most of the code is written in C and that it comprises 2.5 Megalines of code, roughly. One may wonder why it is possible to write such a complex system and have it work. This is the Erlang programmers view."
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Comment by OSbunny
by OSbunny on Tue 14th Aug 2012 15:23 UTC
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Why is the CPU only 200MHz and manufactured using an outdated 150nm process?

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RE: Comment by OSbunny
by anevilyak on Tue 14th Aug 2012 16:05 in reply to "Comment by OSbunny"
anevilyak Member since:

Radiation hardening. Bear in mind, the Earth's ionosphere and other parts of the atmosphere shield us from quite a bit of that, while out in space and/or on mars, a significant number of cosmic rays and such will be encountered. On hardware that's not radiation-hardened, that will easily result in bits being flipped in memory and transistor states being changed, which will cause things to go wrong quite rapidly. Generally speaking, the smaller the manufacturing process/feature size, the more sensitive it is to that kind of manipulation, and there's a significant added cost and testing needed for radiation hardening (plus relatively limited use cases), which is why it tends to lag a few generations behind the latest consumer products.

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RE[2]: Comment by OSbunny
by zima on Tue 14th Aug 2012 17:47 in reply to "RE: Comment by OSbunny"
zima Member since:

More than "bits being flipped in memory and transistor states being changed" - consumer-grade kinds of hardware would be likely quickly destroyed ( the picture in Radiation effects and environments section)

Now, the ISS does have ~100 Thinkpads onboard that seem to be doing quite well, but:
a) critical systems, in particular the main computers of the station (IIRC, using i386), are rad-hard nonetheless
b) I imagine that one of the reasons for an order of magnitude more laptops than humans is to always have a spare at hand
c) the station is still quite well protected in LEO also by our magnetosphere (hm, and I wouldn't be surprised if the tenuous Martian atmosphere - without magnetosphere - makes things occasionally harder on the rovers, by changing singular high-energy particles into showers of them)

there's a significant added cost and testing needed for radiation hardening (plus relatively limited use cases)

Maybe even most usage scenarios for rad-hard processors are quite content with the amount of processing power they already have? It kinda seems like that for most avionics; or for systems working in direct vicinity to nuclear reactors, particle accelerators, or medical usages of radiation (which generally tend to just transmit readouts, heavy processing done elsewhere).
So it looks that autonomous rovers, space science missions in general (already collecting such vast amounts of ~astronomical data that there's no way to transmit it all - first stages of analysis must be done onboard), might represent even more limited use case.
(plus, the pre-launch preparations usually take something like a decade, can realistically use only what's available a few years before launch)

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