> On Dec 20, 2017, at 1:16 AM, Nigel Williams via cctalk
> <cctalk@classiccmp.org> wrote:
>
> On Wed, Dec 20, 2017 at 4:45 PM, Douglas Taylor via cctalk
> <cctalk@classiccmp.org> wrote:
>> There is a CPU board for sale on ebay, M8189, and it has the usual 3 chips
>> CPU, MMU, FPU. However, there are 2 extra chips and I've never seen that
>> before.
>
> https://en.wikipedia.org/wiki/PDP-11_architecture#Optional_instruction_sets
>
> Microcode ROMs for the CIS (Commercial Instruction Set)
I believe PDP11 COBOL makes use of those if available, and the RSTS kernel will
use the string move instruction for block memory copies if it sees CIS.
paul
