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Received: by minnie.vk1xwt.ampr.org with NNTP id AA69 ; Thu, 28 Jan 93 03:01:50 EST Path: sserve!manuel.anu.edu.au!munnari.oz.au!sgiblab!zaphod.mps.ohio-state.edu!howland.reston.ans.net!paladin.american.edu!gatech!destroyer!mudos!mudos!not-for-mail From: mju@mudos.ann-arbor.mi.us (Marc Unangst) Newsgroups: comp.unix.bsd Subject: Re: [386BSD] Creative Labs CD-ROM drivers - Any progress? Date: 26 Jan 1993 17:38:59 -0500 Organization: The Programmers' Pit Stop, Ann Arbor MI Lines: 31 Message-ID: <1k4ei3INN6kl@mudos.ann-arbor.mi.us> References: <1993Jan20.050758.26030@udel.edu> <1993Jan26.073432.16561@ntuix.ntu.ac.sg> NNTP-Posting-Host: mudos.ann-arbor.mi.us In article <1993Jan26.073432.16561@ntuix.ntu.ac.sg> eoahmad@ntuix.ntu.ac.sg (Othman Ahmad) writes: >Why do say we are stupid when the ATBus version is surely faster than the >SCSI version? I'd be interested in hearing why you think this is so. It would seem to me that the SCSI CD-ROM drive would be faster than a SonyBUS drive, if indeed there is a performance difference (which I doubt, see below). Why? Well, the controller/host adapter provided with the cheap SonyBUS drives is usually an 8-bit unit that is engineered with price in mind, not performance -- since the SonyBUS units are usually the cheaper, lower-end devices. With a SCSI device, the manufacturer doesn't have to include a host adapter in the total development and manufacturing budget, and so can dedicate a higher percentage of the total budget to the drive itself. In addition, SCSI host adapters (at least the ones I'd use in *my* system) are usually 16-bit or 32-bit cards that do bus-mastering DMA. However, I doubt there's going to be any noticable performance difference at all. Keep in mind that with a CD-ROM drive, the bottleneck is getting the data off the CD, not getting the data from the CD-ROM drive to the host. The CD<->drive transfer rate is going to be 150K/s (or 300K/s, if you have one of the fancy double-speed drives), no matter what you do with the host adapter; 150K/s is much lower than the maximum transfer rate of even an 8-bit card using programmed I/O. -- Marc Unangst, N8VRH | "Of course, in order to understand this you mju@mudos.ann-arbor.mi.us | have to remember that the nucleus of the atom | is squishy." | -W. Scheider, from a Physics lecture