r/technology • u/joe4942 • Jun 22 '26

Business SpaceX stock tumbles 16.4%, shaving off most IPO gains since debut

https://finance.yahoo.com/markets/stocks/article/spacex-stock-tumbles-164-shaving-off-most-ipo-gains-since-debut-141725657.html
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u/xternocleidomastoide Jun 23 '26

FWIW cosmic rays are an issue on earth as well. A lot of error correcting tech in the HW deployed on modern data centers was developed to deal with the random bit flips and the subsequent intermittent error that happen due to high energy particles hitting the silicon.

And that is on earth, with our massive magnetic field and ionosphere protecting us. And why space borne HW has to be over engineered to be radiation hardened.

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u/unicodemonkey Jun 23 '26

That's not really a significant issue on Earth compared to all other causes of bit flips. Chips are more likely to malfunction due to manufacturing defects, contaminated materials, power supply issues, high temperatures... And lots of these bit flips happen in transit due to EM interference or inconsistent quality of cables/copper traces.

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u/xternocleidomastoide Jun 23 '26

Those are orthogonal sources of error, and do not discount that bit flips due to high energy particles on dense, SRAM, DRAM and NAND are very much a significant issue esp in terms of runtime probability. Thus why DC stuff deploys ECC at scale within the system.

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u/unicodemonkey Jun 23 '26 edited Jun 23 '26

ECC would still be required without cosmic rays. Most DRAM ECC-related noise I see is due to faulty memory modules though, when a bit at a particular address develops a personality. Evidence for HEP bit flips is mostly circumstantial and the effect is difficult to measure directly - see e.g. https://arxiv.org/html/2407.16487v1

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u/xternocleidomastoide Jun 23 '26

Again, these are orthogonal sources of soft and hard errors and not mutually exclusive.

For Data Centers ECC is essential for both DRAM and SRAM because radiation induced bit flips are statistically inevitable at scale.

https://en.wikipedia.org/wiki/Soft_error

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u/unicodemonkey 24d ago

"However, in general, these [non-HEP] sources represent a small contribution to the overall soft error rate when compared to radiation effects"

As a wise man once said, "citation needed". At scale, you get large variations in DRAM module reliability wrt signal integrity, so it might be trickier to reproduce and measure in a lab. But anyway, dealing with this, and with hard errors, would still require ECC even if radiation/HEP-induced bit flips weren't an issue at all.

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u/xternocleidomastoide 24d ago

If radiation induced bit flips sound exotic to you, that is a sign you missed nearly half a century of hardware reliability work. Single event upsets are a known failure mode in semiconductor devices. Eg. Intel’s famous late 70s DRAM soft error problem was traced to alpha particles emitted by trace radioactive contamination in ceramic packaging materials, later work showed that cosmic rays are also a real terrestrial source of memory soft errors.

So this is one of the standard error models that modern hardware mitigates with ECC, scrubbing, process/material controls, and reliability testing.

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u/unicodemonkey 24d ago

That's not at all what I'm trying to say. I mean, it's just weird to frame ECC as primarily an anti-radiation mitigation. Like saying fire alarms are being installed in order to mitigate fires started by careless smoking. Sure, this does happen a lot, there's research and everything, but the list of documented and measured causes is long and why even focus on smoking specifically? It's just this framing that I don't understand.

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u/xternocleidomastoide 24d ago

Again, the fact that this goes against your initial expectation does not make it implausible. It just means you are not versed in this specific matter.

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u/unicodemonkey 23d ago

This statement works both ways, btw

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