On Sun, 30 Nov 1997, Doug Ledford wrote:
> On 30-Nov-97 Rogier Wolff wrote:
> >I'm not sure that you understand what termination is.
>
> If you say so :)
>
> >If you have a cable, and hoist one end of it from 0V to 5V in a few
> >ns, the other end will take a while before it notices that you did
> >that (speed of light at least). Worst case the other end will have a
> >completely different wave form, and you will have trouble deducing what
> >the other end did to generate this. However with a small trick, you
> >can make the wave form travel intact along the wire (the "transmission
> >line effect"): you have to make the conductor be surrounded by a
> >cylindrical grounded plane. Coax. This effect is reasonably strong: A
> >grounded wire on both sides of the conductor in a flat cable is already
> >a reasonable approximation of the coax leading to the transmission
> >line effect.
>
> And is the reason that SCSI cables have 50 or 68 pins (80 if your
> differential SCSI). Of those 50 pins, 25 are ground pins, of the 68 pins,
> 34 are ground pins, etc. However, this does not yet hit on the real need
> for termination.
HUNH !!!!!, Differential is available for -ALL- numbers of
pins & under diff. the number of ground pins is a hell of alot
less. Doug I know you know this .. !
50 pins covers scsi-I & scsi-II
68 pins covers scsi-II & scsi-III
80 pins covers Seagates SCA .
...snip very good explanation...
>
> ----------------------------------
> E-Mail: Doug Ledford <dledford@dialnet.net>
> Date: 30-Nov-97
> Time: 13:34:30
> ----------------------------------
>
, JimL
+-----------------------------------------------------------------------+
| James W. Laferriere - Network Engineer - babydr@nwrain.net |
| System Techniques - 25416 - 22nd S. - Kent, WA 98032 |
| Give me VMS -or- Give me Linux -but- only on AXP |
+-----------------------------------------------------------------------+
|-> Linux-Vax Port, Now in Progress !YAY! there's Progress To Report <-|
|-> Please See http://ucnet.canberra.edu.au/~mikal/vaxlinux/home.html <-|
|-> Maintainer: Michael Still mikal@blitzen.canberra.edu.au <-|
+-----------------------------------------------------------------------+