Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!usc!zaphod.mps.ohio-state.edu!mips!redwood.mips.com
From: wje@redwood.mips.com (William J. Earl)
Newsgroups: comp.sys.mips
Subject: Re: TCP/IP on RC6280
Keywords: trailers
Message-ID: <44720@mips.mips.COM>
Date: 10 Jan 91 19:18:50 GMT
References: <1991Jan9.144544.22626@sobeco.com>
Sender: news@mips.COM
Reply-To: wje@redwood.mips.com (William J. Earl)
Organization: MIPS Computer Systems Inc.
Lines: 25
In-reply-to: stacy@sobeco.com (s.millions)

In article <1991Jan9.144544.22626@sobeco.com>, stacy@sobeco (s.millions) writes:
> Can some one explain to me why mips runs some of thier machines
> with trailers off (Rx3230 m120 rx2030 and some m2000's) and some
> with trailers on (RC62* and the rest of the m2000's).
> 
> I expect it is a performance issue, but am wonder how big the
> difference will be. I am having to turn off trailers on our
> RC6280 so that it can talk to our DEC 20's.

     RISC/os turns off trailers by default on some systems (generally
those with an integrated Ethernet interface), because hardware
considerations make trailers less efficient.  On other interfaces
(generally the VME-based interfaces), there is little or no difference
in performance, so we allow trailers, in case some other host runs
better with trailers.  That is, RISC/os always accepts trailers on
input, but advertises trailers only when there is no performance
penalty.  There is, in any case, no performance penalty to disabling
trailers between RISC/os systems, so you can freely turn them off on
your RC6280.

-- 
	William J. Earl			wje@mips.com
	MIPS Computer Systems		408-524-8172
	930 Arques Avenue, M/S 1-03	FAX 408-524-8401
	Sunnyvale, CA 94086-3650