Date: Sun, 21 Dec 1997 18:08:37 -0600 From: Karl Denninger <karl@mcs.net> To: Alex <garbanzo@hooked.net> Cc: psh1@cornell.edu, freebsd-hackers@FreeBSD.ORG Subject: Re: your mail Message-ID: <19971221180837.31464@mcs.net> In-Reply-To: <Pine.BSF.3.96.971221154010.25163P-100000@zippy.dyn.ml.org>; from Alex on Sun, Dec 21, 1997 at 03:41:43PM -0800 References: <199712210803.AAA00800@wartch.rih.org> <Pine.BSF.3.96.971221154010.25163P-100000@zippy.dyn.ml.org>
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On Sun, Dec 21, 1997 at 03:41:43PM -0800, Alex wrote: > > > On Sun, 21 Dec 1997 psh1@cornell.edu wrote: > > > Yep. I'll bet that was it. While we are on that subject. Are there any > > devices you can safely plug in or out while running? > > Many non PS/2 devices like AT keyboards, serial mice, adb keyboards and > mice, external scsi devices, and occasionally if you're lucky (or just > stupid) floppy data cables. If you're talking PS/2 devices, probably none > of them. I fried a keyboard by plugging it into the mouse only port (or I > seemed to, perhaps it was something else). > > - alex SCSI devices can only be "safely" unplugged and plugged if the connector is designed for it. Specifically, the power and ground pins have to be longer than the signal pins so that the circuitry (particularly the tri-state buffers on the target device) power up and settle BEFORE you connect their data lines to the bus. You won't be likely to FRY anything if its not, but you will almost certainly glitch the bus - which will usually crash the system (or lock the SCSI bus up entirely - the same effect comes from either, as you're reaching for the RESET switch). You can also destroy the data being transferred at the instant when you do this. The short form is *DON'T DO THAT*, unless you have quiesced the bus first (in which case the glitch generally won't hurt anything, as no data transfer will be in process). -- -- Karl Denninger (karl@MCS.Net)| MCSNet - Serving Chicagoland and Wisconsin http://www.mcs.net/ | T1's from $600 monthly to FULL DS-3 Service | NEW! K56Flex support on ALL modems Voice: [+1 312 803-MCS1 x219]| EXCLUSIVE NEW FEATURE ON ALL PERSONAL ACCOUNTS Fax: [+1 312 803-4929] | *SPAMBLOCK* Technology now included at no cost
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