The rate of cosmic ray intersection is most likely directly proportional to the physical cross section of the silicon. The author uses per-bit empirical data f

The rate of cosmic ray intersection is most likely directly proportional to the physical cross section of the silicon. The author uses per-bit empirical data from 10 years ago, when memory was 100 times less dense, and then extrapolates to the present. It would likely be more correct to use a per-chip (or per cm^2) rate.