[TriLUG] Dealing with bit flips from cosmic rays

[John Franklin via TriLUG]

On May 30, 2021, at 13:37, Charles West via TriLUG <trilug at trilug.org> wrote:
> TL:DR:  Are there software ways to harden a Raspberry Pi Zero against bit
> flips?
> 
> I've been looking into space craft design and found some interesting things
> related to computing for space missions.  The common way to do computation
> is to have special hardened hardware that can handle a lot more radiation.
> These things can mass kilograms and run at ~200 mHz while costing $200,000+.

Water is known to be a good radiation shield.  Putting a Pi in a hollow surrounded by several centimeters of water would lengthen the serviceable lifespan of the Pi.  The problem is water is heavy, and getting it to orbit is expensive.

Software tricks, such as parity pages of memory, would protect against bit flips in main memory, but that gets harder to do in L2/L3 cache, and near impossible to do with CPU registers, at least on a stock Pi.  Also, that protects against bit flips, but not permanent damage to the DRAM resulting in stuck bits.

NASA has a really cool flame experiment where they point a camera towards a pair of wires with loops at the end to hold a bit of flammable material and light it.  One of the images from the experiment is here [2].  The dots in the background of the image aren’t stars.  They're damaged bits of the CCD suffered from hard radiation.

If there were a cheaper way, they would already be using it.

jf
[1] https://space.stackexchange.com/questions/1336/what-thickness-depth-of-water-would-be-required-to-provide-radiation-shielding-i <https://space.stackexchange.com/questions/1336/what-thickness-depth-of-water-would-be-required-to-provide-radiation-shielding-i>
[2] https://www.flickr.com/photos/nasamarshall/9935162654/ <https://www.flickr.com/photos/nasamarshall/9935162654/>
-- 
John Franklin
franklin at elfie.org