Comment by wizzwizz4

Skimming appendix H of https://courses.grainger.illinois.edu/cs423/sp2011/lectures/..., I can't see any special treatment of the zero page, but https://stackoverflow.com/a/22847758/5223757 contains an anecdote about SPARCs not placing a page of zeroes at that address. I expect that's probably an OS restriction, and they considered it safer to modify the in-house software they understood, rather than tinker with the externally-sourced OS's memory management routines, but the anecdote is weak evidence that it might have been a hardware distinction at one point.