Dave wrote:
Was going to replace the failing hard drive, and bought an IDE replacement
on the advice of someone I can no longer remember. Now it doesn't look like
the drive that is in there. It has what looks like a 40-pin SCSI connector,
and the drive in my Compaq SR1522X has a small connector that fits over an
edge connector about the size of a USB port. Looks like it has 10 or 12
contacts on the top and bottom of the edge connector. Is this a SATA
device? How can I find out what I am actually trying to replace? Used to
repair mini-systems in a business environment, and PCs are a whole new
experience for me. My background and strength is electronics, but I am
willing to takle anything. Would greatly appreciate any advice or
assistance anyone has to offer.

Many thanks,

Dave



The upper left hand pictures on page 9 may help distinguish
between SATA and IDE. IDE uses a relatively wide ribbon.

http://h10032.www1.hp.com/ctg/Manual/c00311113.pdf

SATA is a wafer contact connector. A proper SATA power cable,
has five fat wires coming in, going to fifteen contacts (three per rail).
Some power adapter cables only provide four wires, and lack
the 3.3V power rail. This is not normally a problem, as many
drives are still using nothing but +5V and +12V. Only certain
tiny SSD drives (perhaps now out of production), have a need for +3.3V.

The data cable is thin, and has 7 wafers for contacts. TX diff
pair, RX diff pair, and three grounds (so-called "drain" wires).
All the data for the drive, travels serially, at a very high speed.
The communication is full duplex, as the RX and TX directions are
independent. The diff pairs have shielding, inside the red plastic cover.

The SATA connector was originally designed, for usage in a "back plane"
scenario. That allows server boxes to be built, where 24 drives front-load
and slide into place. And the connector has enough capture, that the drive
connector just snaps into place. Usage in a desktop was an afterthought.
That's why the connector sections, are mounted in the same plastic
framework, to aid capture. Notice as well, that the wafer contacts are
different lengths - this allows things like advanced power and ground,
and protects against illegal signal levels showing up by accident.
If the ground signal connects first, it helps ensure the polarity of
the other signal leads remains correct. So the contacts were never
intended to be exactly the same length, and it's for a reason.

http://www-947.ibm.com/support/entry/portal/sata2.jpg

Later versions of SATA connectors, have latching mechanisms added.
The first generation of connectors were horrible, and could
fall off while the drive was running. Having recognized their
stupid mistake, later generations of connector designs,
attempted to fix this. The metal latch shown in your SR1522X manual,
is an attempt to keep the connectors from falling off.

Paul