[SystemSafety] [External] Re: Cosmic Ray(?) Bit Flip

[Driscoll, Kevin]

> more likely to have derived from impurities in the semiconductor

... or the packaging.



An interesting case is the experiment where a databus IC was subjected to a radiation source that caused continual Byzantine failures after the radiation source was removed.  The problem cleared when the IC was reset.  An SEU caused by the radiation source had flipped a bit in the register that set the bus speed, making the speed slightly off from the speed used by the other nodes on the bus.  Manufacturing tolerances in the other nodes’ oscillators meant that some nodes saw messages from the affected node OK and others didn’t, leading to inconsistent system states (repeatedly).



-----Original Message-----
From: systemsafety <systemsafety-bounces at lists.techfak.uni-bielefeld.de> On Behalf Of Peter Bernard Ladkin
Sent: Thursday, February 18, 2021 1:20 AM
To: systemsafety at lists.techfak.uni-bielefeld.de
Subject: [External] Re: [SystemSafety] Cosmic Ray(?) Bit Flip







On 2021-02-18 00:07 , Daniel Grivicic wrote:

>

> Here is an example of software going wrong in an entertaining way.

> While entertaining it is something that could be used as a very useful real-world example.

>

> https://www.thegamer.com/how-ionizing-particle-outer-space-helped-supe

> r-mario-64-speedrunner-save-time/

> <https://www.thegamer.com/how-ionizing-particle-outer-space-helped-sup

> er-mario-64-speedrunner-save-time/>



There is a variable being actively used whose value, to cause the effect being investigated, must be one-bit different from the value it had going in.



That it was caused by a cosmic-ray single-event effect is an an assumption well beyond any evidence.

If it was a SEE, since it was occurring at (roughly) sea level it is more likely to have derived from impurities in the semiconductor.



AFAIK (late '90's) the only sea-level SEEs known to have occurred through cosmic rays have occurred to MOSFETs. The reason they are known is because the bit has latched, not just flipped, and the change can be seen when you investigate the component. It requires high energy to latch a bit, and such high energies are mostly found in cosmic rays. If it just flips, there is no evidence, and you have no idea why it flipped.



SEEs do happen at altitude, say 50K feet. Concorde flights registered them on detectors.



A gauge of the author's understanding of the subject can be obtained from the statement "In extreme cases, these upsets have caused planes to fall out of the sky and elections to give thousands of impossible additional votes to candidates....". He hasn't a clue what he is talking about.



PBL



Prof. Peter Bernard Ladkin, Bielefeld, Germany ClaireTheWhiteRabbit RIP

Tel+msg +49 (0)521 880 7319  www.rvs-bi.de<http://www.rvs-bi.de>









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