Re: rescan scsi

Matthias Urlichs (
20 Jun 1997 20:37:37 +0200

" ;The Doctor What" <> writes:
> I have a question....why do people say NOT to add scsi devices on the
> fly to a system? I thought that was (inpart) the point of SCSI?
No. SCSI is not designed for hot plugging.

> 2) There is a chance of an electrical discharge that frys hardware....


A SCSI bus really is a high-frequency system. This means that when you play
with the bus, you have varying electrical capacity on the wires while
you're in the process of plugging the device in or out (and if you're
messing with terminators it gets worse -- MUCH worse). This means that you
can create spikes on the wire that exceed tolerances. I.e., the input gates
of the chips get fried.

I did that once too often. Result: One fried Adaptec 1542 (I still have the
thing -- still dead). Two fried peripherals, luckily they had standard NCR
chips which I was able to replace, after convincing the d*mn distributor to
drop their $1000-minimum-order policy just this once. :-(

You _do_ need to make sure that the bus is quiet while you're plugging
things in or out, preferably by shutting down the system. Even better,
though probably not strictly necessary these days: turn off the power of
all devices on the bus.

> 3) You might accidentally be sucked into the computer and be forced to
> play silly 80's games involving frisbees and glowing cycles.
Ahh, TRON... still one of the best.

I like your game but we have to change the rules.
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