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SubjectRe: Rescan IDE interfaces
On Wed, 6 Jan 1999, George Bonser wrote:

>> Just for the record (I know this is a reply to an old posting,
>> but...) I've hotswapped a few IDE drives and have had no problems
>> at all. a call to hdparm to spin the drive down, then unplugged
>> it and it worked fine.
>
>You got lucky.

Yes, I know. The first time was an accident, after that, I
posted to this list, and many people replied that they
purposefully do it, and have done it for years. Only 2 people
out of about 30 have ever had trouble. The machines I'm doing
this on are shit. Someone could walk up and grab them and drop
them off the CN Tower and I wouldn't much care. The drives are
old < 80Mb Conner/Western/Seagate stuff and are useless anyways.
I use them like a zip drive of sorts...

> One of the problems with most IDE drives is that unless
>the connector is designed for hot swapping, there is no guarantee which
>pins will make/break contact first. It is possible, in some cases, to
>damage hardware because contact is made in the wrong order. If data
>signals are present before the main power or if there are (as there
>usually are) several different supply voltages (usualy two positive
>voltages and one negative), the order that they are applied can be
>important. Connectors designed for hot-swap have pins of differing lengths
>so that the circuits are broken/restored in a known order.

Yep. I'm surprised that I've been so successful with it so far.
Then again, CMOS chips are static sensitive too, and every
digital electronics book goes out of the way to point this out,
and to mention handling and storage precautions to take with
those chips. Nonetheless, with chips <= $2.00 that are easily
replaceable, I've been quite careless with, as are most people I
know, and I've yet to see any bad CMOS chips due to this poor
handling - even in rooms with a relative humidity below 20% in
wintertime. So, the precautions could save the chips, but lack
of precaution doesn't mean they'll fry either.

We shouldn't eat raw meat either. ;o)

>Plan the downtime and swap the drive/cable. What you risk is damage to the
>controller and all drives on the bus. It might work 49 out of 50 times but
>that one time will kick your ass and it might happen the first time you
>try it or the 50th. I know a guy that used to hot-swap drives too. He
>doesn't anymore. Planned downtime is always a LOT better than unplanned.

I agree with you. I wouldn't swap my new Quantum FB like that
for sure! This is just hotswapping old crap equipment that is
worthless, and downtime is meaningless.

It is good of you to point all of that out though, to make people
aware that might not have been that are reading this thread. It
would suck if someone swapped an expensive drive and fried their
drive and motherboard.

Take care,
TTYL


--
Mike A. Harris - Computer Consultant - Linux advocate

Linux software galore: http://freshmeat.net


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