On  2 Dec 98 at 12:15, Javier Vizcaino wrote:

> After reading the very detailed solution below, my question is:
> does the standard care about the inexistent 8 bits (for a 16 bits
> transfer on the 68 pin disk from the 50 pins controller, would have
> to do instead two 8 bit transfers), or that doesn't work at all?

  In order to do wide SCSI, you need:

(a) a wide-capable controller,

(b) a wide-capable drive (or other device...),

(c) a 68-pin connection between them with no intervening partial
termination (I'd rather not explain that in detail...),

(d) successful "negotiation" of the wide protocol between controller
and device.

  Notice item (d).  The wide controllers I've used (Adaptec) allow
you to enable/disable wide negotiation on a per-device basis.
Without successful negotiation, the controller and drive are going to
stick to narrow/fast/ultra 8-bit SCSI as if there were only a
50-pin connection between them.
  [I've seen a failure where a wide controller and wide drive really
were connected with a 50-pin cable and negotiation was left enabled.
The drive and controller apparently agreed to talk wide, but the
narrow cable caused symptoms very like a drive failure.  Turning off
negotiation worked until I could get a 68-pin cable.]

David G

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