8 Apr
2001
8 Apr
'01
1:53 a.m.
On Sat, 7 Apr 2001, Tony Duell wrote:
To what level of detail, Tony? I have a copy of the Maxtor Product Spec
and OEM Tech Manual for the XT-8000E/EH drives that I can extract some
information from.
- don
Tony is (almost) correct: ESDI drives use a binary select scheme similar to
SCSI. The three select bits are decoded to enable drives 1,2,...,6,7.
There's no "drive 0" because that corresponds to the "deselect all
drives"
condition.
Oh, right. I wondered if it did... Incidentally, is the ESDI spec
available anywere (or at least a signal description)? However, some
PC controllers only support two drives (another legacy of the
IBM PC BIOS) and of course they use drives 1 and 2. Therefore, some PC
manufacturers suggest using a cable with a twist, to swap pins 26 and 28
(DS1 and DS2), leaving the select jumpers the same on both drives. I've
never seen a cable with a twist on a "real" ESDI system.
I wondered about that, too (it was an obvious way for a twist to be able
to swap drives 1 and 2). I assume from this that the drive select lines
are not used as data lines for anything else, then (unlike SCSI, say,
where the same 8 lines are used both to select a particular unit and to
transfer commands and data).
-tony