Another DCJ11 oddity

[Jerry Weiss]

On 7/10/18 2:38 PM, Noel Chiappa via cctalk wrote:
>      > From: Jerry Weiss
>
>      > See http://simh.trailing-edge.com/semi/j11.html for information on the
>      > design of the J11.
>
> Thanks for that pointer; I don't think I've ever seen that - quite
> interesting.
>
> Alas, it didn't have the cache info - but now that I've though about it
> overnight, I'm pretty sure the reason for the two bits that do the same thing
> is for -11/70 compatability.
>
>
There is mention in the J-11 specification documents stating 11/70 and 
11/44 features were the target.      The force miss CCR bits are present 
in both, to allow for segregation of the cache(s).  Thus the 
compatibility may span both.    Interesting to note that if there were 
feature conflicts, these where solved in favor of the 11/44 except for 
special cases.

You can find copies in 
http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp11/j11

Jerry