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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.mira.net.au!news.netspace.net.au!news.mel.connect.com.au!munnari.OZ.AU!news.ecn.uoknor.edu!feed1.news.erols.com!howland.erols.net!news.mathworks.com!fu-berlin.de!news.apfel.de!nntp.uio.no!nntp-oslo.UNINETT.no!nntp-trd.UNINETT.no!not-for-mail From: sthaug@nethelp.no (Steinar Haug) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: NCR or Symbios SCSI Controller Date: 21 Dec 1996 20:44:38 GMT Organization: Nethelp Consulting, Trondheim, Norway Lines: 23 Message-ID: <59hi7m$fq3@verdi.nethelp.no> References: <32B5B05F.77E0@zedat.fu-berlin.de> <E2q37p.L4L@cogsci.ed.ac.uk> NNTP-Posting-Host: aun.uninett.no In-reply-to: richard@cogsci.ed.ac.uk's message of Fri, 20 Dec 1996 17:28:37 GMT Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:32913 [Richard Tobin] | >But am I right that they eat some of the bandwidth of the bus? | >They have parts of the SCSI driver in RAM, so they have to | >read from RAM from time to time. | | I think you're confused. The thing that's unusual about many NCR | adaptors is that they don't have a BIOS rom on the card, rather it's | part of the motherboard BIOS (which is why they only work with | suitable motherboards). This makes no difference to performance, | and in any case the BIOS isn't used by BSD except when booting. I believe the original poster is at least partly correct. As far as I know, the NCR/Symbios 53c810 and 53c815 SCSI processors have to fetch all the SCSI 'SCRIPTS' commands across the PCI bus, while the 53c825 and 53c875 SCSI processors have 4 kByte of static RAM for storage of 'SCRIPTS' commands on chip. Thus for instance the ASUS SC200, which is based on the 53c810, will indeed use *some* bus bandwidth. I have no idea just how much - maybe Stefan Esser can tell us? Steinar Haug, Nethelp consulting, sthaug@nethelp.no