Hard Drive Speed

[Tim]

On Sat, 2007-11-03 at 12:54 -0400, Ric Moore wrote:
> Just for ducks, why would they set the drive to half speed? Think it
> might have failed some reliability test at the factory?? Am I about to
> bork my drive if I find it set to half-speed and return it to full? I
> know that any answer would be pure speculation, but I want to make a
> reasonable decision.

Quack!  

As far as I understand it, as mentioned in the instructions for some
SATA equipment I had a play with some time ago, it was to make the
drives compatible with older 1.5 Gig/sec host hardware.  That point of
view is re-inforced on a wikipedia page, but I never know how much to
trust those pages.

http://en.wikipedia.org/wiki/Serial_ATA

>From the "SATA 3.0 Gbit/s" section:

"Backward compatibility between SATA 1.5 Gbit/s controllers and SATA 3.0
Gbit/s devices was important, so SATA/300's autonegotiation sequence is
designed to fallback to SATA/150 speed (1.5 Gbit/s rate) when in
communication with such devices. In practice, some older SATA
controllers do not properly implement SATA speed negotiation. Affected
systems require user-intervention to manually set the SATA 3.0 Gbit/s
peripherals to 1.5 Gbit/s mode, generally through the use of a
jumper.[2] Known faulty chipsets include the VIA VT8237 and VT8237R
south bridges, and the VIA VT6420 and VT6421L standalone SATA
controllers.[3] SiS's 760 and 964 chipsets also initially exhibited this
problem, though it can be rectified with an updated SATA controller
ROM."

So, as far as I can see, it'll just offer a speed increase (where
possible).  If your find your drive won't work when jumpered that way,
I'd expect that you could put the jumper back on and go back to running
at half speed.

-- 
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Using FC 4, 5, 6 & 7, plus CentOS 5.  Today, it's FC7.

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