Re: ATA anomaly Question

[Bill Hacker <wbh@xxxxxxxxxxxxx>]

Joerg Sonnenberger wrote:

> On Sun, Mar 20, 2005 at 03:31:28AM +0800, Bill Hacker wrote:
>
> > >   Typically the cable is reversed (motherboard side is connected to the
> > >   drive and the drive side is connected to the motherboard) when the
> > >   message occurs for a standard PATA drive and the cable is 
> > >   UDMA-capable.
> >
> > Most sockets & headets are keyed (blocked pin position) to prevent
> > that (at least on the better cables I try to use). Ground leads 'float'
> > at one end, are collected at the other end, IIRC.
>
>
> The problem is that you can indead use both sides for UDMA33 and slower,
> but need to use the correct side for UDMA66+. IIRC it was related to the
> different timing of signals, but I might be wrong.
>
> Joerg

Not only timing of signals, but the encoding/decoding methodolgy
and addition of error-correction.

But the cables differ by having extra embedded ground/shield wires - 
more like SCSI,
where every second wire has always been a ground in a flat cable.

There is a decent explanation here:

http://www.interfacebus.com/Design_Connector_IDE.html

The IDE connectors did NOT originally do that - the data wires were 
side-by-side,
leading to cross-modulation with fast pulse rise times, so extra wires were
embedded, then gathered at one end and tied to 2 ground pins.

This allowed the connector to stay at 40 pins (others exist, but are 
rarely seen).
- though still only at a fraction of the allowable length for SCSI or 
SMD, let
alone DVD SCSI or HP-Parallel Current Loop.

As Matthew pointed out, the 'message' about not finding the cable (on a 
SATA port)
is superfluous/gratuitous/irrelevant.

Bill