From:	HENRY::IN%"gkn%sdsc-sds.arpa%kl.sri.com%csnet-relay.CSNET%relay.cs.net@RCA.COM"  6-JUN-1987 20:40
To:	info-vax@kl.sri.com
Subj:	Promiscuous mode vs. padding

Mike:

Your problem is PADDING, a hack whereby the first two bytes of the data
portion of the ethernet frame are used to contain the length.  Prior to
VMS V4.5, the DEUNA driver (XEDRIVER) assumed that padding was ENABLED,
even for promiscuous mode UCBs.  If the value in the first two bytes of
the data portion of the frame is sufficiently large, and the CXB falls
near the end of non-paged pool, you'll get an ACCVIO in routine MOVBUF
(called from IOC$IOPOST, in module IOPOST) when VMS goes to copy the
buffer back to your address space.

The solution is to disbable padding on the promiscuous mode unit, which is
done with the parameter NMA$C_PCLI_PAD (2842 decimal).  $NMADEF is in the
macro library SYS$LIBRARY:LIB.MLB, by the way.

gkn
--------------------------------------
Arpa:	GKN@SDSC.ARPA
Bitnet:	GKN@SDSC
Span:	SDSC::GKN (27.1)
USPS:	Gerard K. Newman
	San Diego Supercomputer Center
	P.O. Box 85608
	San Diego, CA 92138
AT&T:	619.534.5076
