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From: gkendall@ncr-mpd.FtCollins.NCR.COM (Guy Kendall)
Newsgroups: comp.periphs.scsi
Subject: Re: speed difference on external drives?
Message-ID: <726@ncr-mpd.FtCollins.NCR.COM>
Date: 28 Feb 91 16:31:40 GMT
References: <1991Feb23.194013.13400@unixland.uucp>
Reply-To: gkendall@ncr-mpd.FtCollins.NCR.COM (Guy Kendall)
Organization: NCR Microelectronic Products Division
Lines: 22

In article <1991Feb23.194013.13400@unixland.uucp> bill@unixland.uucp (Bill Heiser) writes:
>
>Does having a SCSI drive external to a 386 system, on a cable
>several feet long, affect the data transfer rate?  Is it significantly
>better to have the drive mounted internally in the system?
>

If you are using asynchronous SCSI, then the cable length does affect
the transfer rate. If the external cable is only several feet long,
then it should not make any noticable difference. I once heard that the 
SCSI signals travel at around 5.25 nS/meter and if you are only talking
several feet then this will not add much at all to the transfer period.

If you are using synchronous SCSI, then it is not supposed to make
any difference at all.
 

-- 
Guy W. Kendall - Applications Engineer   gkendall@ncr-mpd.FtCollins.NCR.COM
NCR Microelectronic Products Division          Voice: 719-596-5795
1635 Aeroplaza Drive                             Fax: 719-570-6045
Colorado Springs, CO 80916                       BBS: 719-596-1649