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Newsgroups: comp.os.386bsd.questions Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!saimiri.primate.wisc.edu!news.doit.wisc.edu!psl.wisc.edu!128.104.200.15!ram From: ram@xor.epi.wisc.edu (Ram Bhamidipaty) Subject: Re: VLB IDE cache controller In-Reply-To: yaot@hardy.u.washington.edu's message of 21 Sep 1993 08:46:40 GMT Message-ID: <RAM.93Sep21145412@xor.epi.wisc.edu> Sender: news@pslu1.psl.wisc.edu (USENET News System) Organization: Physical Sciences Lab, UW-Madison References: <27mf1g$ajt@news.u.washington.edu> Date: 21 Sep 1993 19:54:12 GMT Lines: 39 >>>>> ">" == <yaot@hardy.u.washington.edu> writes: >> NNTP-Posting-Host: hardy.u.washington.edu >> Hi there: >> I just upgraded my old ISA IDE controller to >> a VLB cache version. >> ... However, after some thorough test, >> I notice that the cache controller doesn't seem to improve >> the I/O performance at all. >> Does Netbsd support VLB cache controller ? or I need some kind >> of driver ? Or does cache controller help at all? I'm no expert...but: 386bsd and its derivatives have a sophisticated caching system that predict what blocks from the disk will be needed and also try to optimize how the disk head moves across the surface to minimize the amount of time spent waiting for head movement (which dominates the amount of time disk accesses take). Note that DOS is a totally different case, since it does not optimize head motion and does no caching on its own (I hear that there are packages that do this, like smartdrive...) Thus I would expect almost no benefit from a caching controller, since the cache system in 386bsd is already doing that job. A VLB controller might be able to speed transfer rates, but an IDE controller can only handle two disks, which can be handled by the ISA bus. A SCSI VLB controller on the other hand would be a big win when connecting several drives. -Ram -- -------------- Ram Bhamidipaty use this ->ram@epidat.epi.wisc.edu Department of Preventive Medicine or this->ram%epidat.decnet@macc.wisc.edu University of Wisconsin, Madison Ignore the header. It might be wrong.