The Soul of Barb's New Machine was creat 1151
I've used it, albeit on a i386 ~20-33 MHz and I didn't think it sucked.
Yes, and? It meant that all the parts were eminently proddable, making it an ideal tool for an OS lab course, but far less for conquering the world.
As far as I know, this was mainly done to let Minix run on a 8086 peecee, which was just about affordable to the average IT student in the eighties. Tanenbaum used more machine language than strictly neccessary, to let Minix run at all on a floppy-only 8086.
Paraphrasing the coursebook 1:
ss 1.2.5 Minix is designed for code readability and compatibility with Unix v7 (then heavily restricted), portability, and the ability to run from a floppy diskette.
What happened about 1990 was that hordes of disgruntled Unix fans such as Theo de Raadt desperatedly wanted a Unix of their own and put Tanenbaum under pressure to accept their (crufty) improvements.
Tanenbaum refused, as he imho rightfully thought that that wasn't his job. His main focus at the time was reseach on the Amoeba distributed operating system.
8086 memory space was: The Soul of Barb's New Machine 1152
The 8080 had a way to derive stack access, but not the Z80. Nor was the M1 a...
1 Andrew S. Tanenbaum, 'Operating systems. Ontwerp en implementatie', Academic Service 1987
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