31 Dec
2007
31 Dec
'07
9:22 a.m.
From: pete at dunnington.plus.com
---snip---
There was a signal on some drives that came on the data cable.
I think it may have been a write protect but I don't recall
exactly what it was. The ST506 may have used this signal.
I'm not sure if this is what he is talking about.
There's a "drive selected" signal, but I think most drives have that.
It's there because the 34-way control cable is daisy-chained but the
20-way data cable is radial, one per drive. I'd suspect things like step rate and number
of heads would
be more important to him than anything else.
The other important difference between the ST506 signals and the ST412
was that the ST506 didn't support buffered seek; the timing of the step
signals had to be slow enough that the stepper motor could keep up. The
ST412 was the first drive that buffered the step signals, so they could
be sent rapidly, and virtually every hard drive after that did too.