From owner-freebsd-hackers Thu May 23 14:28:34 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id OAA21744 for hackers-outgoing; Thu, 23 May 1996 14:28:34 -0700 (PDT) Received: from irz301.inf.tu-dresden.de (irz301.inf.tu-dresden.de [141.76.1.11]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id OAA21659 for ; Thu, 23 May 1996 14:28:16 -0700 (PDT) Received: from sax.sax.de by irz301.inf.tu-dresden.de (8.6.12/8.6.12-s1) with ESMTP id XAA11006; Thu, 23 May 1996 23:27:20 +0200 Received: by sax.sax.de (8.6.12/8.6.12-s1) with UUCP id XAA11581; Thu, 23 May 1996 23:27:20 +0200 Received: (from j@localhost) by uriah.heep.sax.de (8.7.5/8.6.9) id UAA18349; Thu, 23 May 1996 20:52:33 +0200 (MET DST) From: J Wunsch Message-Id: <199605231852.UAA18349@uriah.heep.sax.de> Subject: Re: 960501-SNAP: data corruption reading /dev/rwt0 (Wangtek) To: freebsd-hackers@freebsd.org (FreeBSD hackers) Date: Thu, 23 May 1996 20:52:33 +0200 (MET DST) Cc: gwk@cray.com Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) In-Reply-To: <199605231500.RAA05186@racer.dkrz.de> from "Georg-W. Koltermann" at "May 23, 96 05:00:06 pm" X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E X-Mailer: ELM [version 2.4ME+ PL17 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk 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. ;-)