*BSD News Article 21592


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From: burgess@hrd769.brooks.af.mil (Dave Burgess)
Newsgroups: comp.os.386bsd.questions,comp.periphs.scsi
Subject: Re: CDs and SCSI
Date: 28 Sep 1993 08:58:35 -0500
Organization: Armstrong Laboratory, Brooks AFB, TX
Lines: 25
Message-ID: <289fup$967@hrd769.brooks.af.mil>
References: <CE29yI.IKt@festival.ed.ac.uk> <CE2AF7.AA@veda.is>
NNTP-Posting-Host: hrd769.brooks.af.mil

In article <CE2AF7.AA@veda.is> adam@veda.is (Adam David) writes:
}richard@castle.ed.ac.uk (Richard Tobin) writes:
}
}>There seem to be numerous CD rom drives on sale that are sold with
}>SCSI adaptors much cheaper than the adaptors supported by BSD (Adaptec
}>etc).  What is the difference between these adaptors and the supported
}>ones?  Obviously they may require different drivers, but are the
}>adaptors themselves inherently less capable?
}
}You might find that they are not DMA busmasters, so you could end up using
}more CPU cycles pushing all that data around. You might also find them slower
}for this or any other number of reasons. Wasn't someone working on an ST-02
}driver?
}

Isn't the amount of CPU used for these types of transfers something like
17 cycles + 2/byte?  At 20Mhz, that is a herd of data in a second.

It seems to me that Glen Overby at plain.nodak.edu was working on it.  I
haven't heard much on it an a while.
-- 
------
TSgt Dave Burgess
NCOIC AL/Management Information Systems Office
Brooks AFB, TX