A Mozilla engineer's analysis of 470,000 crash reports indicates that memory bit flips cause up to 15% of Firefox crashes. These bit flips, where a memory cell unintentionally changes value, can be triggered by electrical issues, hardware defects, aging components, or even cosmic rays.
The data suggests half of these bit-flip crashes stem from genuine hardware problems, though the exact contribution from cosmic rays remains unknown. The engineer emphasizes that all devices with memory, from PCs to smartphones, are susceptible to such errors.
The main topics covered are the significant proportion of software crashes caused by hardware memory errors, the various causes of bit flips, and the universal susceptibility of electronic devices to this phenomenon.
Memory bit flips cause up to 15% of Firefox crashes, asserts Mozilla engineer — figure inferred from 470,000 auto-submitted crash reports
Some proportion of these bit flip-induced crashes will be due to a cosmic ray passing through.
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A Mozilla engineer has shared survey data and calculations suggesting that up to 15% of Firefox crashes are due to a bit flip. For the purposes of this report, a bit flip occurs when a memory cell (RAM, cache, etc) updates its value from 0 to 1, or vice-versa, following some unintentional external input. The most common triggers for bit flips are thought to be electrical issues and instability, thermal effects, underlying manufacturing defects and aging, crosstalk, and even memory cells being flipped by an ionizing cosmic ray.
No one seems to have a hard figure for the biggest bit flip contributor. However, systems sent to space will use specialized components hardened to resist interference from cosmic radiation, extremes of temperature, etc, and to include aggressive error checking.
The Mozilla team received nearly half a million auto-submitted crash reports last week (opt-in feature). Data from a recently introduced “memory tester that runs on user machines after the browser crashes,” guided senior engineer Gabriele Svelto towards his eyebrow-raising bit flips, causing 15% of crashes figure, which he admits “dwarfs all the previous estimates I saw regarding this problem.”
Mozilla employed, self-confessed ‘old school nerd’ Svelto says that an initial 10% estimate was revised up because “If I subtract crashes that are caused by resource exhaustion (such as out-of-memory crashes) this number goes up to around 15%.” Moreover, it was determined that one in two bit flip crashes was due to a “genuine hardware issue.” Svelto notes this could be undershooting the real figure as Mozilla’s memory test on crash feature “only checks up to 1 GiB of memory and runs for no longer than 3 seconds.”
Thus, it is hard to drill down to probably the most fascinating statistic of how many Firefox crashes are precipitated by an errant cosmic ray passing though…
As a parting shot, Svelto doesn’t want fancy Arm-based MacBook owners, or any other niche device owner, thinking this is just about PCs with shaky RAM. Every device with memory can be affected by bit flips, asserts the engineer. That doesn’t matter if it’s a Mac, smartphone, or even a printer or router. From that perspective, PC desktop DIYers are probably in a better position, as they can replace any faulty component without throwing away the whole caboodle. But please, great cosmic ray caster in the sky, please don’t make me think I have RAM issues in 2026…
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Mark Tyson is a news editor at Tom's Hardware. He enjoys covering the full breadth of PC tech; from business and semiconductor design to products approaching the edge of reason.
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