ATA100 cable Pin #34 (CBLID)

  • Thread starter Thread starter V W Wall
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V W Wall

I recently installed a Seagate ST380013A 80GB drive. Since there was
an eighty conductor cable there already, I merely substituted the new
drive for the old slave using the old cable. I then transfered the OS
and other files to it and changed the cable and jumpers to make it the
master, and set the old drive slave. I just noticed that the 80 wire cable
that came with the new drive has the wire from pin 34 cut just after
the motherboard (blue) connector. The old cable does not have this cut.

I know that pin 34 is used to detect the presence of 80 wire cables.
Everything ia working OK with the cable with the un-cut wire. Just
wondered why Seagate would cut the wire in the cable they supplied
with the drive. Anybody know?

Virg Wall
 
From: V W Wall (e-mail address removed)
Date: 01/04/2004 8:00 PM Eastern Standard Time
Message-id: <[email protected]>

I recently installed a Seagate ST380013A 80GB drive. Since there was
an eighty conductor cable there already, I merely substituted the new
drive for the old slave using the old cable. I then transfered the OS
and other files to it and changed the cable and jumpers to make it the
master, and set the old drive slave. I just noticed that the 80 wire cable
that came with the new drive has the wire from pin 34 cut just after
the motherboard (blue) connector. The old cable does not have this cut.

I know that pin 34 is used to detect the presence of 80 wire cables.
Everything ia working OK with the cable with the un-cut wire. Just
wondered why Seagate would cut the wire in the cable they supplied
with the drive. Anybody know?

Virg Wall
--
Click to expand...

Pin 34 is grounded in the motherboard connector (that's how the BIOS detects
the 80 wire cable), and the wire is cut so that the drive doesn't see a ground
on that pin (don't know what effect it would have on the drive). Perhaps your
old cable had the wire isolated in some other way. I have 2 cables, one has the
cut you described, the other does not, but it metered out the same.
 
ChrisJ9876 said:
Pin 34 is grounded in the motherboard connector (that's how the BIOS detects
the 80 wire cable), and the wire is cut so that the drive doesn't see a ground
on that pin (don't know what effect it would have on the drive). Perhaps your
old cable had the wire isolated in some other way. I have 2 cables, one has the
cut you described, the other does not, but it metered out the same.
Click to expand...

I'm aware of the grounding of pin 34 on 80 wire cables. The Seagate Barracuda
7200.7 Product Manual shows pin 34 marked as (DDIAG-CLBID) and connected to both
the slave and master connectors. A "cut" connector, as in the cable supplied
with
their own "Baracuda" ST 380013A drive would obviously prevent this. Restance
measurements show connectivity between pin 34 on master to slave connectors.

There is another statement (P 23): <quote>

"The drive detects the 80-conductor cable by sensing a capacitor at the host
side
through the CBLID- signal. The result is reported in a Fast Rise Detected bit
(bit 13 of word 93 in the Identify drive parameter block)."

I wonder how it can do this if the CBLID (34) pin is connected to ground.
Every recent MB I have seen checks this pin for ground on 80 wire cables.

My attention was called to this when the BIOS was taking a long time to identify
the drives. I changed the HD cable and noticed the "cut" in the new cable. The
problem turned out to involve the ATAPI drives on the secondary controler.
I left the cable with the "uncut" wire to pin 34 in place, so I can't check
it for the pin 34 connection. "If it works don't fix it!"

It always bothers me when I know more about something than I understand. ;-(
It happens often with Windows, but I can sometimes find the answers.

Virg Wall
 
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