Date: Sun, 16 Nov 1997 13:14:43 -0800 From: David Greenman <dg@root.com> To: Mark Mayo <mark@vmunix.com> Cc: hackers@FreeBSD.ORG Subject: Re: de underflow errors. huh? Message-ID: <199711162114.NAA21266@implode.root.com> In-Reply-To: Your message of "Sun, 16 Nov 1997 14:59:10 EST." <19971116145910.31953@vmunix.com>
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>On Sun, Nov 16, 1997 at 12:45:44AM -0800, David Greenman wrote: > > >> >de0: abnormal interrupt: transmit underflow >> > >> >I have no clue what this means. Packets seem to be flowing through >> >the interface nicely, and there is no noticeable packet loss. >> >If anyone has any ideas what could be causing this, or if I should >> >give a hoot, please let me know. >> >> It's indicating that the PCI bus was sufficiently busy enough to cause >> the transmit DMA to be stalled too long. The proper response to this condition >> in the device driver it to dynamically increase the transmit threshold (the >> number of bytes that are DMA'ed onto the card before the transmission is >> actually started on the wire). The fxp driver does this, the de driver >> doesn't. I think Matt Thomas might have fixed this in a later rev., but I'm >> not sure about that. >> Anyway, other than the annoying console messages and perhaps a packet >> drop when it happens, the problem can be ignored. > >Do you think increasing the bus speed will make a difference? This machine >is a P54C 150 - I originally wanted to run it at 75MHz * 2, but the >dealer gave me one of the aftermarket Intel CPUs with the integrated >heat sink, and the machine just plain won't make it past the memory >check when I run the bus at 75... I've done this (75*2) setup on several >other machines with no problems - but they had the OEM'ed version of the >CPU with no heatsink, and a grey bottom. I'm guessing that this black >bottomed jobby is preventing itself from being "overclocked" somehow. >I may try and get a replacement CPU.. But before I do that do you think >the jump from 60MHz to 75MHz will help the de card? I don't know. > Or is the 100Mb fxp >simply delivering data too quickly for it to handle. Perhaps replacing >the de with a fxp... That would get rid of the problem. You didn't mention which chip was on the de card, but if it is the original 21140, then that might also be a problem - I seem to recall that it didn't do the memory-read-multiple PCI operation, resulting in very poor PCI performance. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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