[Simh] VUPs?

[John H. Reinhardt]

Norman Lastovica wrote:
> in at least one case that I can think of, a VAX was purposefully slowed
> down in the microcode.  that is, at least, the rumor while I worked there.
> I'll bet Bob Supnik has some insight and stories along these lines.
>
> Care to share Bob?
>   

I'm not Bob, but from things that I've read I believe that it's the VAX 
8600 and 8650 that you're thinking of.  The tale is that the 8600 
microcode had a multitude of NOPs which were removed for the 8650 and 
were responsible for a large portion of it's speed increase.  IIRC the 
claim was that the NOPS were used much like NULs after carriage return 
characters in the old teletypes - i.e.  to create a certain amount of 
slack time to allow hardware operations to finish (or something similar).

  John H. Reinhardt