[COFF] machine code translation,as mental architecture models

[John Levine]

It appears that Dave Horsfall <dave at horsfall.org> said:
>On Sat, 12 Jul 2024, John R Levine wrote:
>
>> Our Vaxes ran Unix so it was all C other than a few things like tracking 
>> down a bug in the 11/750's microcode that broke an instruction in the 
>> inner loop of printf().  [...]
>
>Do tell...

The details are a litle dim after 45 years, but there was a MOVTUC
instruction in the inner loop of printf that scanned for the null at
the end of the string.  The /750 had a microcode bug that didn't
matter for the way DEC's software used it but broke the libc and
I think also the kernel version.  MOVTUC sets six registers and
we probably used one they didn't.

Bill replaced it with a few simpler instructions and the comment

	; Comet sucks

R's,
John

PS: For you young folks, Comet was DEC's internal project name for the /750.