[pseudohadamard]

They're not advertised as such but they are. I don't have any current evals to hand but a 25-year-old paper that looked at things like the PIII concluded that "Intel processors verge on radiation-hardened devices" and another more recent one that "No apparent device degradation was apparent on any of the samples. Cumulative dose levels for exposures ranged from 1 to 17 Mrad(Si). For comparison, the ITAR level is 500 krad(Si). As noted, total dose and DR device tolerances exceed the ITAR limits for this [AMD A4-3300, 2011 vintage budget desktop CPU] off-shore fabricated design. To the best of the authors’ knowledge, AMD has not intentionally radiation hardened the device for these environments, but the technology itself supports these characteristics". IBM and Sparc CPUs are the same, tested under proton or neutron bombardment, but they don't publish dose rate figures, just FIT or MTTU.

[evan_a_a]

Modern process nodes with smaller feature sizes are likely to fare far worse under radiation than the nodes of 25 years ago.

Additionally, total dose is only one part of the equation. Single Event Effects (SEE) also must be mitigated.

You can read NASA JPL's ASIC design guidance for a brief intro.

https://parts.jpl.nasa.gov/asic/Sect.3.4.html#A0