Can anyone comment on whether MMIX is still used for teaching? I figure it makes more sense to just teach, say, AArch64, these days. I'm not convinced that enough is gained by using an 'idealised' instruction-set, to balance out that it's not seen in the real world.
Also, here's the Wikipedia page on MMIX. It's even supported as a target by GCC. https://en.wikipedia.org/wiki/MMIX
While this is an interesting book in its genre, I prefer to read actual MMIX code in The MMIX Supplement by Martin Ruckert[0]. The relation between the two books resembles that between, say, Manual of Surgery and Frankenstein, or Teach Yourself Romanian and Dracula.
[0] https://www.amazon.com/MMIX-Supplement-Computer-Programming-...