At 23:40 28-02-98 GMT, Bill wrote:
>What is wide SCSI?  Is this due to the fact the cable is wider then
>regular SCSI?

In narrow SCSI, a byte (8 bits) of data is sent out along 8 data lines in
parallel. (Other lines carry ground, control signals, power, etc. Every
other line is a ground line to shield the signal carrying lines from each
other.) With each clock cycle, a byte of data can be transferred along the
SCSI bus.

In wide SCSI, two bytes is sent along 16 data wires that are in parallel.
For each clock cycle, two bytes can be transferred. So the data transfer
rate is doubled in wide SCSI by doubling the width of the data path
(doubling the number of data lines). There are also more ground wires (for
shielding) and more control lines. With wide SCSI, twice as many SCSI devices
can be handled by adding another "addressing" bit. Yes, the cable is wider
for wide SCSI. (68 lines compared to 50.)

Note that in *ultra* SCSI, the data transfer rate is doubled by doubling
the clock rate. (Twice as many signals moving along each line each second.)
Wide and ultra would give four times the data transfer capability of narrow
(non ultra) SCSI.

Regards,
Bill