[colechristensen]

It would be quite hard to gather that data and would be highly dependent on hardware and source of bit flip.

But there's volatile and nonvolatile memory all over in a computer and anywhere data is in flight be it inside the CPU or in any wires, traces, or other chips along the data path can be subject to interference, cosmic rays, heat or voltage related errors, etc.

[ZiiS]

It should be fairly easy to see statistically if ECC helps, people do run Firefox on it.

The number of bits in registers, busses, cache layers is very small compared to the number in RAM. Obviously they might be hotter or more likely to flip.

[bpye]

I believe caches and maybe registers often have ECC too though I'm sure there are still gaps.