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John,

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From:    John Waaser <[log in to unmask]>
Subject: Drive "controllers"

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Someone said:

Ok, I'm starting to believe this :)   Paraphrasing, does the command
and response go through the "controller" in the machine through to the
real electronics that run the drive?   It almost has to be working, as
Linux partitioning tools reported the full size of the drive.  Given
that much, is safe to assume Linux can access it?

In my old days as owner of Crossroads Computer here in town, I used to
do warranty service on several mail-order computers such as Comtrade,
Pony, and others. I recall the time that the son of someone I knew had
just gotten a Comtrade for Xmas, and was having problems with it. The
error message reported a hard drive controller problem. The standard
response to that was to replace the motherboard. I guess that the
thought there was that the hard drive interface was the same as the
controller, and that was on the MB, right?

Well, folks, IDE stands for Integrated Drive Electronics. The controller
is on the hard drive, and what is on the motherboard is just the
interface through which that controller speaks to the processor and
whatever else it needs to speak with.

Comtrade sent a new motherboard, and paid me to go out and exchange it.
Of course the motherboard was not exactly the same. Specifically, the
new motherboard, shipped bare, was supposed to take a cache RAM card,
while the cache RAM was soldered to the original MB. After exchanging
the MB, the computer failed to boot at all. (As, we, the enlightened
would surely suspect....) Anyway, I opined that the problem was likely
with the drive, and suggested that I could return it to its original
configuration and replace the drive and it would work. The 15-yr-old
spoiled-rotten kid called Comtrade, and told them what I said. The tech
rep told the kid that the repair guy didn't know what he was talking
about, and that the two of them together were going to fix the computer
over the phone. After 45 minutes of having this kid poke and prod inside
where he had never seen before, they finally decided they'd send out a
new MB of the same type as the original one.

When I got the call that the MB had arrived, I asked if they had shipped
a drive with it. The kid's mother said that there was a package in there
about the right size, but I picked up my workbench hard drive anyway.
When I arrived, the only thing there was the MB and a package of cables
and such. When I changed out the board, it was back to its original
configuration and behaving exactly as it had. This is February, and the
Xmas present had never worked. I then unplugged the hard drive, plugged
in my workbench drive, and the computer booted. When Comtrade shipped a
new hard drive, and paid me for a third visit to repair the computer, it
worked fine.

The drive controller is on the drive. The only thing on the MB is a path
for communication.

And sometimes it's fun showing the customer just who does not have a
clue what they are talking about!
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Your reply includes:
==============================
Well, folks, IDE stands for Integrated Drive Electronics. The controller
is on the hard drive, and what is on the motherboard is just the
interface through which that controller speaks to the processor and
whatever else it needs to speak with.

The drive controller is on the drive. The only thing on the MB is a path
for communication.
==============================

I am not sure what to make of your reply.  I quoted "controller" because
I was fairly certain that the MB (or in-slot board) was indeed just an
interface to the "real electronics that run the drive".  I think we are
saying the same thing.

Beyond anything else I should be asking, I am curious whether the
interface board could be sufficiently dated as to prevent a recent Linux
kernel from successfully talking to the on-drive controller of a new[er]
IDE drive.  More specifically, if Linux says "it's time to format your
500GB drive" and that drive is indeed 500MB, then is it safe to assume
that Linux can write to the entire drive?

Bill




Wilhelm K. Schwab, Ph.D.
University of Florida
Department of Anesthesiology
PO Box 100254
Gainesville, FL 32610-0254

Email: [log in to unmask]
Tel: (352) 846-1285
FAX: (352) 392-7029