Date: Thu, 23 May 1996 20:52:33 +0200 (MET DST) From: J Wunsch <j@uriah.heep.sax.de> To: freebsd-hackers@freebsd.org (FreeBSD hackers) Cc: gwk@cray.com Subject: Re: 960501-SNAP: data corruption reading /dev/rwt0 (Wangtek) Message-ID: <199605231852.UAA18349@uriah.heep.sax.de> In-Reply-To: <199605231500.RAA05186@racer.dkrz.de> from "Georg-W. Koltermann" at "May 23, 96 05:00:06 pm"
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As Georg-W. Koltermann wrote: > Not really. You see, that data corruptions does not happen randomly > (and of course I know more today than I knew yesterday). > > a) Every point of corruption that I checked is exactly 512 bytes of > data being replaced by binary zeroes. That's exactly one tape > block. It sounds like a DMA problem. I remember the drive worked for me until recently, that is, about two months ago. I haven't tested it ever since (and it's currently on loan to some other FreeBSDer around). > I think there is a software problem with the wt driver, maybe related > to doing DMA on a 32 MB machine (bounce buffers?). Whether the Normally, you don't need (explicit -- i.e. the config option) bounce buffers, since wt isn't a bus-master DMA device, but rather uses the lame motherboard DMAC. The motherboard DMA code used to have bounce buffers all the time, and if that one were broken, your floppies wouldn't work either. (It needs it also for transfers that span a 64 KB boundary.) > Is there an easy way how I can restrict my machine to using just the > lower 16 MB of memory, so that bounce buffers will not be needed? options "MAXMEM=16384" > Out of curiosity, does anyone run a wt type tape with an ISA bus > adapter on a machine with more than 16 MB memory? Nope, my spam machine has only 8 MB, and that's where the wt tape is normally located. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)
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