Date: Sat, 31 May 1997 11:13:49 +0200 From: j@uriah.heep.sax.de (J Wunsch) To: freebsd-chat@FreeBSD.ORG (freebsd-chat@freebsd.org) Cc: francisco@natserv.com (Francisco Reyes) Subject: Re: IDE or Ultra SCSI Message-ID: <19970531111349.YK60956@uriah.heep.sax.de> In-Reply-To: <199705301538.LAA02031@federation.addy.com>; from Francisco Reyes on May 31, 1997 00:50:37 %2B0000 References: <199705301538.LAA02031@federation.addy.com>
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As Francisco Reyes wrote: >From my understanding IDE can do one command "per channel". `Channel' is a confusing term. Spell it as `controller', and you have something you can compare with other architectures in our (Unix) world. Still, you are limited to one outstanding command per controller with IDE, while you can have many outstanding commands per controller with SCSI. And while it is common that you are limited to two controllers with IDE, there's no obvious limit for the number of SCSI controllers you could plug in, other than the number of slots available. See wcarchive. Remember, FreeBSD has been able to talk to two ST-506 controllers long before this was common practice in the PC world. I assume one machine running at my previous employer was one of the very first (if not the first one at all) running 386BSD with two wdc controllers (one IDE, and one WD1007V ESDI). I had to patch the wdc code for this, it must have been late 1993. The machine is still running these days (with FreeBSD 1.1.5.1), although the ESDI drive has been retired. > I decided to stay with SCSI, but I am talking to the vendor to see if > they can get me plain SCSI (Adaptec 2940 instead of 2940U) and just > plain old SCSI-2 drives. Nay. Labelling drives as SCSI-3 (is this really standardized already?) and controllers as Ultra is the marketing hype you gotta live with. The older non-Ultra controllers and drives that are labelled just SCSI-2 are no longer being built. The 20 MHz `Ultra' feature is turned off by default. Unless you've really got more disks to talk simultaneously than 10 MB/s, don't turn it on. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)
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