On 18 Jan 2011 at 14:18, Shoppa, Tim wrote:
Isn't it wonderful the way the pendulum swings?
First parallel
cylinder select (e.g. SMD and other bus and tag type address
interfaces), then step in/out cylinder select (e.g.
SA4000/SA1000/ST-506) and serial cylinder select (e.g. ESDI), then
parallel cylinder select (e.g. IDE/ATA/SCSI), then serial cylinder
select (e.g. SATA).
It would seem to be more a matter of "smarts on the disk drive" than
anything. IDE/SCSI and SATA all have controllers on the drive and so
have no dedicated signal lines for positioning. In particular
IDE/SATA LBA and SCSI don't require any knowledge of the drive
geometry, other than the sector size and the total number of sectors.
with ST506/412 and ESDI, the "smarts" were still external to the
drive.
Earlier drives had some smarts in the drive, particularly for
positioning, which doubtless contributed significantly to the price
of the drive.
--Chuck