This is turning-on-scanner:-dangerous? in view mode; [Up]
Date: Sun 31-Oct-1991 16:12:32 From: dcarpent@sju.edu (D. Carpenter) Subject: turning on scanner: dangerous? I discovered recently that it is possible to turn on an HSD scanner and get the NeXT to recognize it without powering down the NeXT first. This is very convenient, but is it dangerous? Do I risk doing damage to my computer by not powering down prior to turning the power on on the scanner? Thanks for any advice
Date: Sun 02-Nov-1991 16:19:19 From: jiro@shaman.com (Jiro Nakamura) Subject: Re: turning on scanner: dangerous? (YES) In article <1991Oct31.161232.276@sjuphil.uucp> dcarpent@sju.edu (D. Carpenter) writes: > I discovered recently that it is possible to turn on > an HSD scanner and get the NeXT to recognize it without > powering down the NeXT first. This is very convenient, > but is it dangerous? Do I risk doing damage to my > computer by not powering down prior to turning the power > on on the scanner? Yes there are risks: 1) It is definitely NOT a good idea to have powered down devices on the SCSI bus. When their controllers are powered down, they may respond strangely to bus signals intended for other machines. Keep all of your SCSI devices powered up at the same time. This problem is not uncommon, but since only some devices exhibit this behaviour, not many people are aware of it. 2) When you finally do power up the device, depending on its specs. it may do a bus reset. This is a Bad Thing. Or it could just plain be confused for the couple of milliseconds until it figures out what had happened to it. In other words, if you want to keep your data safe (imagine if your drive does a Write command just when your other device comes up and some bits are tranposed/trashed), just keep them powered up. - jiro
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