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Newsgroups: comp.os.386bsd.development Path: sserve!newshost.anu.edu.au!munnari.oz.au!sgiblab!swrinde!cs.utexas.edu!math.ohio-state.edu!caen!usenet.coe.montana.edu!decwrl!netcomsv!netcom.com!jmonroy From: jmonroy@netcom.com (Jesus Monroy Jr) Subject: Re: [FreeBSD 1.0R] DMA Problems? Message-ID: <jmonroyCJ3u56.1us@netcom.com> Organization: NETCOM On-line Communication Services (408 241-9760 guest) X-Newsreader: TIN [version 1.2 PL1] References: <jmonroyCIHJA2.oy@netcom.com> <2fl24q$jn2@u.cc.utah.edu> <JTW.94Jan3234318@pmws.lcs.mit.edu> Date: Tue, 4 Jan 1994 12:17:30 GMT Lines: 68 John Wroclawski (jtw@lcs.mit.edu) wrote: : In article <jmonroyCIvwpv.8F3@netcom.com> jmonroy@netcom.com (Jesus Monroy Jr) writes: : To clarify the issue: DMA DRAM refresh skipping would be a : bad term to use. What happens is the timer for channel 0, : the DRAM refresh timer, is reprogrammed so that there are : less refreshes per second (ie. 2000 new vs. 3000 old refreshes : per second)... : It is possible, via software, to reprogram the refresh cycle. : My example program does this. The results are had when the : system crashes. That is, to make this a software *probe* : the program would (if it existed for *BSD) slowly turn down : the timer till the system crashed. At this point, some : test could readily determine the *consistency* of ths system. : This won't work very well. : It is impossible to -probe- for a minimum DRAM refresh rate because : the answer is not binary. If you avoid refresh for long enough, yes, : the data will flat-out be lost. But long before that the DRAM will : simply become much more sensitive to power supply noise, cosmic rays, : lightning, and all of the other things that occasionally cause DRAMS : to lose data. Unless you can duplicate all of these external events : during your probe operation, you cannot even begin to predict when the : RAM will fail. : I'm sorry for this reply... but Sagitarius (sp?) won't align with the moon for at least four days.... Can I give you an answer then? What is this "cosmic ray" stuff? Somebody please tell me if I should take this seriously? : For what it's worth most DRAMS operating at room temperature will hold : bits fairly well for at least ten times longer than the specified : refresh interval. This value falls rapidly at higher temperatures. At : the specified maximum operating temperature, the longest time you can : wait safely is fairly close to the listed refresh interval. : Look, here are the facts.... There are tweleve women of asian decent with a birth defect rate of about 50% that produce these chips. Companies with mucho bucks pay them next to nothing to work like slaves..... Two days a week they get drunk and 7 of the 12 women make the chips you and I will be testing next week... Please quote the literature... or at least the the K&R book. Tell me I'm an idiot or something... but please... enough speculation.... : John Wroclawski : jtw@lcs.mit.edu -- Jesus Monroy Jr jmonroy@netcom.com Zebra Research /386BSD/device-drivers /fd /qic /clock /documentation ___________________________________________________________________________