Subject: Re: DEQNA trouble.
To: None <port-vax@NetBSD.ORG>
From: John Wilson <>
List: port-vax
Date: 07/29/1999 20:41:07
FWIW, I sifted through a lot of assorted driver code when I was doing the
DEQNA emulation for my PDP-11 emulator, and found that the manuals lie
(or at the very least they're too vague).  I forget the exact details, but
anyway it appears that all that talk in the manuals about bits encoded in
the length of a SETUP packet, refers to the length *after* converting it
back to a positive byte count and processing the bits for high-byte-start
and low-byte-end (one of which I think they claim was dropped on the DELQA?
anyway each one deducts one from the actual length).  It's possible I read
the code wrong (please tell me if so!), some of the drivers I saw seemed to
have strange combinations of expecting the bits to be set before or after the
negate-and-divide-by-two though, so I think this has caused some confusion
in the past as well.

John Wilson
D Bit