-----Original Message-----
From: cctalk-bounces at
classiccmp.org [mailto:cctalk-bounces at
classiccmp.org]
On Behalf Of Mouse
Sent: Thursday, May 15, 2014 1:47 PM
To: cctalk at
classiccmp.org
Subject: Re: Help with Access to Old Hard Drive
I don't recall the specifics as to why they used
80 conductor wired
for a 40 pin connection; I believe it had something to do with
reducing crosstalk & interference at the higher speeds of the (at that
time) newer hard drives.
The version I saw is that the other half of the wires are grounded at the
CPU end and exist as shielding for the other lines - basically, as you say,
to reduce crosstalk and other intra-line interference.
While I'm a good deal less sure of this, I also have the impression that
there is some other difference - an otherwise unused pin grounded in the
connector? - which (a) serves to notify the host electronics that it's got
an 80-wire cable and (b) means that the host connector is operationally
different from the drive connectors (which isn't the case for 40-wire
cabling).
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You could use an 80 wire cable even on the old drives, but it would not make
any difference. To make a difference, the connector on the motherboard had
to be something other than black (usually blue). 80 pin cables allowed for
faster access to the data on hard drives. 80 pin cables also provided
additional capabilities; if connected to a CD or DVD, you did not have to
use a sound cable to get music from the speakers. ATA33 was the original,
then ATA66, then ATA100, then ATA133.
Cindy