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A comment on History of Xenix – Microsoft's Forgotten Unix-Based Operating System. Parent comment

Re:History of Xenix – Microsoft's Forgotten Unix-Based Opera... by TheOtherHobbes on Friday October 07, 2016 @03:40PM (#12663392)
ROM boot was only true of 8-bit micros. The standard for mainframes and minis was to boot an OS from tape/disk/(paper tape.)

OS choices and OS upgrades happened regularly. You could run all sorts of things on a PDP/11, VAX, DG Nova, etc.

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Re:History of Xenix – Microsoft's Forgotten Unix-Based Opera... by pjmlp on Friday October 07, 2016 @04:06PM (#12663550)
No, it was also the way in the Amiga, Mac and Atari, the floppies only had a partial implementation, all 16 bit.

As for the mainframes and minis, I never worked with them, besides the AS/400.

But from my collection of old papers and manuals, many of them had "bytecodes" with microcoded execution (more higher level than plain CISC Assembly) burned on their processors.

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Re:History of Xenix – Microsoft's Forgotten Unix-Based Opera... by slrz on Saturday October 08, 2016 @07:03PM (#12669117)
Yes, some were microcoded. And you were able to replace that microcode with your own creations!

See for example this paper, where they took a VAX and rewrote its microcode so that it executed instructions for the Warren Abstract Machine, the output format of their Prolog compiler.

It's like you would reprogram your Core i7 to directly consume JVM bytecode.

http://hps.ece.utexas.edu/pub/gee_micro19.pdf

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Re:History of Xenix – Microsoft's Forgotten Unix-Based Opera... by pjmlp on Sunday October 09, 2016 @11:31AM (#12671636)
Thanks for the link.

I was a big Prolog fan during my degree.

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Re:History of Xenix – Microsoft's Forgotten Unix-Based Opera... by digi_owl on Saturday October 08, 2016 @02:21AM (#12665915)
Supposedly even the original PC had a BASIC boot option.

And frankly, its design is not that far from the other micros (ISA cards can extend the BIOS by responding to specific memory address ranges, much like a ROM cart on a C64). Its just so damn well wallpapered over these days.

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