On 15 Nov 98 at 3:02, Uzi Paz wrote:

> There are quite a lot of standards for SCSI outlets and sockets, there are
> at least two types of 50pin (external), there are 40pin, 25pin, 68pin
> sockets.

  40 pins is IDE, not SCSI.

> 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 suspect that most of this is achieved by using a common ground
return instead of one per signal line.

> I am now interested in mapping between 50pin old (big socket)
> standard and the 25pin, and the mapping between the 68 pin and the
> new (small socket) 50pin standard.

  68-pin connectors are WIDE SCSI, with 16 instead of 8 data lines
and 4 instead of 3 device address lines.  68-to-50 adapters come in
two basic types:  those that provide termination for the unused
lines, and those that do not.  If you use one that terminates those
lines, the bus beyond the 50-pin device will still work for narrow
devices (unless the rest of the lines are terminated by the
device...) but is unlikely to work for further wide devices even
though the physical connectors on the cable still have 16 pins.

David G

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