https://en.m.wikipedia.org/wiki/Heisenbug

Thanks for the updates! I’ve been really enjoying seeing this coming along. Looks amazing.

I think one of the motivations for having separate modes like this, with (some) separate registers for each, is to reduce the time taken to switch contexts between modes. If they didn’t have separate registers, the data in the user mode registers would have to be saved somewhere when making a switch into kernel mode, and then copied back again when switching back to user mode.