From owner-freebsd-alpha Sun Nov 28 13:42:41 1999 Delivered-To: freebsd-alpha@freebsd.org Received: from alcanet.com.au (border.alcanet.com.au [203.62.196.10]) by hub.freebsd.org (Postfix) with ESMTP id 98F7714BEE for ; Sun, 28 Nov 1999 13:42:37 -0800 (PST) (envelope-from jeremyp@gsmx07.alcatel.com.au) Received: by border.alcanet.com.au id <40335>; Mon, 29 Nov 1999 08:35:12 +1100 Content-return: prohibited Date: Mon, 29 Nov 1999 08:42:20 +1100 From: Peter Jeremy Subject: Re: de0: abnormal interrupt: transmit underflow In-reply-to: <19991126131515.C2EB21C6D@overcee.netplex.com.au> To: Peter Wemm Cc: alpha@FreeBSD.ORG Reply-To: peter.jeremy@alcatel.com.au Message-Id: <99Nov29.083512est.40335@border.alcanet.com.au> MIME-version: 1.0 X-Mailer: Mutt 1.0pre3i Content-type: text/plain; charset=us-ascii References: <19991126131515.C2EB21C6D@overcee.netplex.com.au> Sender: owner-freebsd-alpha@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On 1999-Nov-27 00:15:15 +1100, Peter Wemm wrote: > Main memory should >be plenty fast enough to keep up, as it's a good 500+mbyte/sec, and we only >need in the order of 12kbyte/sec to keep the transmitter busy. ^M >It's as though the chips have a bug and "forget" about keeping the fifo >full. I half thought I saw Bill Paul say he was suspicious that it's >something to do with the descriptor layout and that keeping the transmitter >running from a contiguous mbuf cluster rather than collecting the frame >from multiple mbuf fragments might be the solution. Given exactly the same warning message in Compaq Tru64 (aka Digital UNIX aka OSF/1), it looks to be a hardware bug, rather than a driver error (unless we have managed to replicate a bug in DEC's code[*]). A fault in the FIFO management seems the most likely. Since the Tx underflows generate rubbish on the wire, is there any way to initialise the chips so they start with 1024 byte FIFO's when running at 100mbps? This would somewhat increase latency, but would reduce the number of garbage ethernet frames generated. Peter [*] Though I've read about experiments showing that this is more common than would be expected. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message