18 Oct
1999
18 Oct
'99
6:29 p.m.
On Mon, 18 Oct 1999, Bill Sudbrink wrote:
Well, the Shugart 801s and 851s had a jumper that permitted selecting
between 800/850 characteristics and 801/851 characteristics. The
difference is hopefully explained by the following:
The drive
don't care. It's the media that is important in this case as
soft sector has only one index hole and the hard sector for NS* uses
11 holes(index plus sectors).
Ah... That makes sense. Although I thought that the index hole
was in a different position. Is the same (drive don't care) true
for 8 inch drives as well?
Some of the old 8" drives (Shugarts included) did
have the hard-sector
jumpers, but that was to accomodate a peculiarity in the
8" interface.
An 8" drive in hard-sector mode delivers both an index and a sector
pulse. Mostly, the hard-sector jumpering brought into play a couple of
one-shots. Unlike the READY signal, this was never carried over to the
5.25" drives. The READY signal, oddly enough, wasn't present on the
Shugart 400 5.25" original, but was added when 100 tpi drives came along.
Now, most drives with more than 40 cylinders offer an option setting
(even if it's a trace cut) to select disk change or ready. Few 48 tpi
5.25" drives, however, do. One surmise is that this was to make
migration from 8" drives easier.
- don