Date: Wed, 18 Sep 1996 12:15:12 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: durian@plutotech.com (Mike Durian) Cc: freebsd-hackers@freebsd.org Subject: Re: Special Cycles on the PCI bus Message-ID: <199609180245.MAA03300@genesis.atrad.adelaide.edu.au> In-Reply-To: <199609180133.TAA05262@pluto.plutotech.com> from "Mike Durian" at Sep 17, 96 07:33:23 pm
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Mike Durian stands accused of saying: > We have not been able to track down what is generating these > cycles. We can reproduce them reliably on two system (that is > all we've tested on). The commonality between the two systems is > the Triton chipset and an ISA ethernet card (3c509). As for There is regular timer-initiated activity with the 'ep' driver which would appear to correlate with the symptoms you describe below. > Though we don't know much, we do know the following: > 1) The "Special Cycles" only start appearing when the root > file system is mounted. We think we've tracked it down > to the VOP_OPEN call in ffs_vfsops.c. This happens on > both the SCSI and IDE systems. Is there any other activity (eg. starting of timers) which happens at some interval before this? Is it possible that you're arriving here by coincidence or are you breakpointing beforehand? > 3) On an idle system in single user mode and the cable removed from > the ethernet card with the PCI bus analyzer set to trigger > on "Special Cycles" and interrupts we saw only two types > interrupts, these had values 0x20 and 0x28. Their timings > appeared to be 10ms and ~8ms appart. From this I'd assume > them to be the two system clocks. "Special Cycles" would > invariably follow the interrupts approximately 11us later > (though sometimes only ~6us). There seemed to be some cause > and effect. Did you have the 'ep' driver active at this point in time? If you disable the 'ep' driver using userconfig, do these cycles still show up? > 4) On a non-idle system the behavior was not as well behaved. > "Special Cycles" did not always follow the timer interrupts, > sometimes there were other interrupts in between. I'm > guessing that perhaps the timer interrupt was interrupted > by the other before the code the resulted in the "Special Cycle" > was executed, but this is just a guess. There might also be other activity hung off the timer. > 5) According to the databooks we have, none of the chips in the > system generate "Special Cycles". Yet they appear. And > malformed to boot. Are they causing you serious grief? > mike -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] Collector of old Unix hardware. "Where are your PEZ?" The Tick [[
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