>>Can anyone advise me if my scsi2 scanner would work with an
>>upgraded motherboard that has an onboard UW SCSI controller
>>or would I need to add in a scsi 2 card.
<snip>
>but for a little more money I would get a cheap host adapter for the scanner
>alone, and leave it off the UW bus completely, you don't want that sucker
>slowing down your disk access if you paid a bunch of money for a UW HD.
"and leave it off the UW bus completely"
Unless you are seriously short of SCSI bus bandwidth
or have a time-critical process on the bus
(in which case _it_ should have its own private bus),
I doubt that you will notice any difference from
the mix of peripherals on the bus: remember that
the SCSI devices are intelligent and SCSI commands
can be overlapped (unlike IDE).
Where you _might_ benefit from having a separate controller is
in termination independence and cable length:
* if the the scanner is on an independent bus then whether it is
connected or switched on is of little conseqence unless you
intend to use it, whereas if you have a combined internal and
external bus you must ensure it is _always_ correctly terminated
for your SCSI devices to work (though that needn't mean you
have to keep your scanner on);
* you probably won't need to worry about cable length
read "How long can my SCSI bus be?" (see table below)
<http://www.ultranet.com/~gfield/gary/scsifaq.html#_Hlk407004683">
and asynch devices on the other bus may run faster on a short bus
read discussion in "Is the NCR 53C90 Faster than spec?"
<http://www.ultranet.com/~gfield/gary/scsifaq.html#_Hlk410546217> .
From the SCSI FAQ <http://www.ultranet.com/~gfield/gary/scsifaq.html>
"The SCSI length limits are based on the speed of the fastest device
attached to the bus. Here's a table which shows the limits:
Speed of FASTEST device Max. single-ended bus length
5 MHz (SCSI1 synch.) 6 metres
10 MHz (SCSI2 FAST) 3 metres(not rec.)
20 MHz (Ultra or Fast20) 1.5 metres(not rec.)
40 MHz (Ultra2 or Fast40) Only differential connections allowed"
Len Warner <[log in to unmask]> WWW Pager http://wwp.mirabilis.com/10120933
Chaos reigns within. Haiku error message
Reflect, repent, and reboot.
Order shall return. -- Suzie Wagner
