31 Jan
2013
31 Jan
'13
9:50 p.m.
I was interested to read about the differences between
the 9121 and
82901 commands, eg the 9121 supports a superset of the 82901 commands
and so should be fully backwards compatible. One difference I have noted
I beleive it was specifically designed to be. It was intended that any
systme that supported the 82901 could also use the 9121, no matter waht
assumptions it made. In this repsect, the respose to the standard
idenmtification coammends is the same, there is one extended command that
returns a differnet value o nthe 2 drives so it is possible to tell them
apart, but a ssytsem designed fo the 82901 wouldn't use that command.
Also the total numebr of sectors per disk is the same -- IIRC the 82901
is double-sided 35 cylidner and the 9121 is single sided 70 cylinder.
-tony