Stan Sieler writes:
>Jon asks:
>
>>      Did you try to use the SCSI A/B Switch?  I have found several
>
>no...I sent it to a friend to try, and I don't know if he put it on
>a 3000 or a Mac.
>
>> I/O Channel.  My thoughts are to make sure the drive is not in use on
>> the
>> first HP3000, down the LDev (possible powering it off???), flip the
>> A/B
>> switch, (power up, if needed), and then up the LDev on the second
>> HP3000.
>
>We've had good luck doing that with an HPIB switch, although HP recommended
>against it in the mid '80s.
>
>Still, I'd be cautious if the ldev to be switched is on a SCSI channel
>with anything else!
 
For what it's worth, there's an item in the APS Technologies catalog
(about whom more later) that they call a SCSI PowerPlug. It claims to
allow for hot-swapping SCSI devices by maintaining signal levels and
termination during the switch, as well as isolating and holding the
handshake lines to prevent either the peripheral or the CPU from starting
a transfer. They have one with a built-in terminator for use at the end
of the chain, and another with a splitter to use within the chain. They
claim that up to two of the splitter-type connectors can be used in a
chain. I haven't actually seen or used one, but it may be worth
investigating.
 
APS is a long-time vendor of Macintosh peripheral products; as most
readers are aware, the Mac has been using SCSI for nine years, so these
people have some experience. I've bought a number of things from them and
been quite satisfied. APS can be reached at (800) 304-7416.
 
-- Bruce
 
 
 
--------------------------------------------------------------------------
Bruce Toback    Tel: (602) 996-8601| My candle burns at both ends;
OPT, Inc.            (800) 858-4507| It will not last the night;
11801 N. Tatum Blvd. Ste. 142      | But ah, my foes, and oh, my friends -
Phoenix AZ 85028                   | It gives a lovely light.
[log in to unmask]                   |     -- Edna St. Vincent Millay