lkml.org 
[lkml]   [1997]   [Mar]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: your mail
    On Mon, 3 Mar 1997, Richard B. Johnson wrote:

    > This is the SCSI driver. No external drives are attached, and the internal
    > drives are connected with a SHORT cable properly terminated on the far end.

    A too short SCSI cable is a no-no. The problem is that a scsi cable is
    actually a transmission line and the points where devices connects are
    essentially points of discontinuity which alter the characteristic
    impedance of the cable. Depending on the impedance of the the drives and
    the impedance of the cable, you can have *too* *short* a cable. I think
    that you will generally be safe with one foot between connections on the
    cable. Less than one foot per connection and the dominating impedance may
    be that of the drives and not that of the cable. because of this, too
    short is bad. I certainly would not use less than 6" of cable between
    connectors (and this only with drives that present not more than 10
    picofarads of capacitance at the scsi interface).

    If you doubt me, then by all means check out appendix C of the scsi 3
    spec. My scsi stuff works f*cking great (I can read and write my md raid
    at 42 MB/s and I am mounting / on /dev/md0 via initrd). I don't doubt
    that there are faster controllers, but my adaptech's are dang reliable.


    Ed Welbon; welbon@bga.com;

    Any sufficiently advanced technology is indistinguishable from linux...
    Flush bill, choose linux.



    \
     
     \ /
      Last update: 2005-03-22 13:39    [W:4.265 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site