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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!metro!metro!asstdc.scgt.oz.au!nsw.news.telstra.net!act.news.telstra.net!psgrain!iafrica.com!uct.ac.za!quagga.ru.ac.za!howland.erols.net!newsfeed.internetmci.com!in2.uu.net!ausnews.austin.ibm.com!usenet From: Tushar Patel <tpatel@austin.ibm.com> Newsgroups: comp.unix.bsd.freebsd.misc,comp.unix.bsd.bsdi.misc Subject: Why one should buy parity memory for reliability? Date: Tue, 24 Sep 1996 22:05:01 +0000 Organization: IBM Austin Lines: 32 Message-ID: <32485B0D.41C6@austin.ibm.com> NNTP-Posting-Host: spur07.austin.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (X11; I; AIX 2) CC: tpatel@ecpi.com Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:27935 comp.unix.bsd.bsdi.misc:4970 Hi, I was going through the FreeBSD hadbook and one of the things suggested in the book is buy "parity memory". I was involve in designing one of the microcontroller for Motorola, one of the things we left out for the future controller was not supporting parity (less pin count). The reasoning was, In the normal condition the error should not happen, if it does then there is somethings seriouly wrong, like having high temprature or more noise in the system. So, the bord designer better design the system correcly. (They had some hard numbers to back the theory and this is just the brif explanation). If the Board supports the parity memory and error occurs then in theory the OS should be notified and the access should be reapeted. Does FreeBSD support such error conditions? What happens in the case of the DMA transfer from the DISK to the memory or from memory to disk, if the memory error occures then processor is not looking at the data bus, so does that mean that the DMA master (SCSI controller) will detect the parity error and retransfer the data? There is a big difference in the price between the parity and non parity memory so I am trying to justify the parity memory purchase. Please make comments. Thanks, Tushar