VAX Compatibility Mode

[Henry Spencer]

> A minute or so with the documentation - in my case, the 1981 edition of
> the VAX Architecture Handbook - reveals Table 17-3 - "Compatibility Mode
> Reserved Instructions" - which lists those PDP-11 instructions that fault
> to native mode (i.e., are not implemented by the hardware).  MARK is right
> in the middle of the list.
> 
> Given the usual high quality of Henry's writing, I was rather surprised to
> see him "shooting from the hit" on something so easy to check.

It's easy to check only if you happen to have a VAX, or at least VAX
documentation, handy.  Fortunately, I don't.  (If you think you detect
some anti-VAX bias... you're right.)  My friend claimed that the absence
of MARK was undocumented; he was probably right at the time.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry