Extra chips in PDP11/23 plus cpu board

Paul Koning paulkoning at comcast.net
Wed Dec 20 07:58:18 CST 2017

> On Dec 20, 2017, at 1:16 AM, Nigel Williams via cctalk <cctalk at classiccmp.org> wrote:
> On Wed, Dec 20, 2017 at 4:45 PM, Douglas Taylor via cctalk
> <cctalk at 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.


More information about the cctalk mailing list