Help! Ethernet configuration

[Steve Glaser]

	I seem to recall the CHAOSNET people telling us that
	the interlan boards belong at the very last unibus
	vector.  I'm still not sure why you would want to
	give them the lowest position in the priority scheme...
	seems to me they should go at the second to the highest position,
	just after your uda50's, and other big-time cards.

	Possibly this will help?

Come on now.  Vector assignment has absolutely nothing to do with
priority.  DMA priority is strictly determined by bus position.  The
only thing that matters on vector assignment is that they not be
overlapping.  [At least on 4.1 and 4.2 where they probe the unibus
space during boot causing interrupts to figure out what's where.]

Thus, the only reason for configuring vectors following any particular
scheme is that it makes it easier to run other systems which aren't as
bright about finding things (say VMS and/or diagnostics).

As for the rationale for putting the Interlans at the end of the bus,
that's easy.  Ethernet protocols already deal with lost/damaged packets
by retransmitting so if you get a data late on a recieve, you can
safely ignore the packet.  Actually on the Interlan card, I don't think
you'll ever get these - you just may miss a few NEW packets due to
buffer space limits on the card.

We have a number of large machines (mostly 780s, some 750s) with lots
of Interlan cards, terminal interfaces (DZ and VMZ), tape drives, etc.
We even had to hack the tm11 driver to deal with more than 4 tape
drives and the dmf32 (aka VMZ) driver to not waste interrupt vector
space.

	Steve Glaser, Tektronix
	steveg.tektronix at csnet-relay.csnet	CSNET/ARPANET
	tektronix!steveg			UUCP