The diagnostic may indeed be easy to capture, but it doesn’t demonstrate the failure.  ☹

From: Paul Koning <paulkoning@comcast.net>
Sent: Sunday, January 30, 2022 8:55 AM
To: HECnet <hecnet@lists.dfupdate.se>
Subject: [HECnet] Re: KG11 emulation probably defective -->diagnostic ZKGAB0 for KG11 runs without complaints.

On Jan 30, 2022, at 12:21 PM, Mark Pizzolato - Info Comm <Mark@infocomm.com> wrote:

On Sunday, January 30, 2022 at 5:34 AM, Reindert wrote:

The diagnostics in XXDP for KG11 completes without problems, so far, so good.
It limits the scope to interface problems between Decnet11MP and Simh KG11.

We really don't know how robust the diagnostic is and if it exercises the same
details that are used by the DDCMP implementation.

You could run the DDCMP case with KG11 debugging enabled and identify what it is doing precisely and then go back and see if the diagnostic is doing the same stuff...

CRC is both straightforward and tricky, so it would not be too strange to have bugs here.  Capturing a SIMH debug trace for the KG device would potentially be informative.  The diagnostic might be the easiest one to capture.

FWIW, PyDECnet has a universal CRC implementation that can be useful as a reference implementation.  The unit test script (tests/test_crc.py) shows test runs for every CRC I have seen described, including lots of extremely obscure ones.

paul