KEV11-B Extended Instruction Set
From Computer History Wiki
The KEV11-B Extended Instruction Set is is reportedly (documentation on it is impossible to find) an optional chip for LSI-11 chip set which adds support for the PDP-11 Extended Instruction Set, but not also FIS floating point (like the KEV11-A).
For the KEV11-B, one version is known, the 23-090A5; it is suitable for the M7270 quad module etch revisions C and D.