on Sunday, November 15, 1998 2:47 AM Uzi Paz wrote:

>I wish to know if there is somewhere how to map between different
>standards, and what do the extra pins mean, i.e. if I use a 50pin to 25pin
>cable what do I lose?
>I am now interested in mapping between 50pin old (big socket) standard and
>the 25pin,

Uzi, on a standard 50 pin SCSI cable, every other pin is "mass" (I'm not
sure if this is the correct term
or if "ground" would be more appropriate, I've been in germany for quite a
while now) which is used for shielding. The 25 Pin external socket just
doesn't use the shielding. This is usually used for slow devices like
scanners, and the cable quality doesn't have to be that good.

>and the mapping between the 68 pin and the new (small socket) 50pin
>standard.

The 68 Pin Socket is for WIDE SCSI (16 Bit), the 50 pin Mini is (as far as I
know) 8 Bit FAST SCSI. You can get an adapter for converting one to the
other, but you will lose your ability to do 16 Bit transfers to the device
you have hooked up (effectively castrating your speed to that device), and
you can't assign a device ID higher than 7 to it. If your thinking about
making your own adapter, you probably are going to have quite a few
problems. SCSI is very, very picky about the cabling (and shielding). The
probems that are caused by reflection and noise on the SCSI bus belong to
some of wierdest.


Rick Swartz ([log in to unmask])
http://www.uuhome.de/richard.swartz
PC-Support  Emission-Monitoring (Air)
BASF

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