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Newsgroups: comp.unix.bsd Path: sserve!manuel.anu.edu.au!munnari.oz.au!sgiblab!darwin.sura.net!paladin.american.edu!news.univie.ac.at!hp4at!mcsun!sunic!sics.se!jonas From: jonas@sisu.se (Jonas Lagerblad) Subject: Re: Weird Problem (50 MHz, SCSI) Message-ID: <1992Oct14.220847.22548@sics.se> Keywords: SCSI, file corruption Sender: news@sics.se Organization: Swedish Institute of Systems Development References: <Bw227w.6Bw@cs.vu.nl> Date: Wed, 14 Oct 1992 22:08:47 GMT Lines: 54 In article <Bw227w.6Bw@cs.vu.nl> versto@cs.vu.nl (C Verstoep) writes: >Hi, > >The last couple of days I have (as of now unsuccessfully) tried to install >386BSD0.1 on my new system. > >My setup is as follows: > - 50 Mhz local bus UMC mother board > - 16 Mb memory, 70ns SIMMs > - Adaptec 1542B scsi controller > - Fujitsu 2624F 520 Mb scsi disk. .... Problem description omitted .... > >By the way, with **DOS5.0 I didn't have this kind of problems, but I guess >that doesn't say much. A colleague of mine has the same system at home, >with similar problems. > >Does anyone here have a clue about what could be the cause of all this? > >Thanks, >Kees Verstoep (versto@cs.vu.nl) I have had quite a lot of problems with two different 50 Mhz cards, I have traced the problem to the cache memory, which I don't think behaves quite all right when using a DMA driven disk controller. In my case the cache memory has an access time of 20 ns and the tag ram 15 ns, and since the cycle time of a 50MHz CPU is 20ns I think it should be quite tight to have 20 ns access time on the memory (even without needing to do a cache lookup). And when the situation is even worse when DMA cycles might appear which might confuse the cache logic this might cause memory corruption. I posted an article to this newsgroup a week ago inquiring if anyone besides me have had problems with their 50MHz boards and I have got approx. 10 answers where most people have had some strange memory problems, most of them had a SCSI controller. My problems have disappeared totally since disabling the cache, but I have ordered new faster cache memory, and is eagerly waiting for it to arrive. According to one of the hardware manuals for my DX50 cards the cache memory should have 15 ns access time and the tag rams 12 ns. (The times can be read on the chips which typically have some marking 67256-20 where -20 indicates the access time of the ram, the number before the dash usually have something to do with the size of the ram. The number I wrote here have no relevance at all with anything). The cache and tag rams can usually be easily found, since there usually are 8 cache rams and 3 tag rams which are not soldered, and sit in a tight formation. (In my case under the power supply :-) So my advice is to try to disable the cache, and see what happens. Best Regards -- Jonas Lagerblad Phone Office: +46-31-830250 Home: +46-31-205955 Car: +46-10-2846031 FAX: +46-31-831047 email: jonas@sisu.se