Friday, 20 September 2013

IDE & ESDI

IDE
Integrated Device Electronics. Under the IDE standard, the controller chip WD 1003 is mounted directly on
the hard disk, not on the IDE adapter. This means that the conversion to parallel data is already done on
the disk. Because of the short serial cable, this increases the transfer speed significantly relative to MFM
and RLL. IDE is a simple adapter. The adapter itself contains only amplifying circuits to/from the I/O bus.
Therefore it is inexpensive. The IDE controller does not care whether the hard disk works internally with
MFM or RLL coding.

ESDI
ESDI is an improvement over the ST506 standard. An ESDI disk operates on a common 16-bit AT bus
(ISA-bus), but it is better put together than an ordinary IDE. This results in an almost doubling of the
transfer speed between hard disk and controller/bus. ESDI is also different in many other ways. Among the
features are a sector on the hard disk which identifies its number of tracks, cylinders, etc. This information
is usually stored in CMOS.

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