Installation guide
COlWPATIBILITY
Interfaces
ST506/ST412
The
ST506/ST412
interface
has
been
an
industry
standard
since
1981.
It
is
primarily
intended
for low-cost.
low-capacity
applications.
This
interface
standard
places
most
of
the
drive
subsystem's
logic
on
the
controller.
The
drive
in
this
installation
is
primarily
a
recording
device.
The
compatibility
from drive
to
controller
is
primarily
centered
around
one
question.
Can
the
controller
properly
handle
a drive
with
the
drive's
characteristics?
These
characteristics
are
number
of
cylinders,
number
of
heads
and
encoding
method
(MFM
or
RLL).
If
the
controller
can
handle
the
drives
characteristics
it
should
be
compatible.
RLL
is
an
encoding
method
that
allows
about
500/0
more
infonnatlon
to
be
recorded
on
a
disk
drive
compared
to
MFM recording.
This
does
not
imply'
that
drives
that
have
been
designed
for MFM
use
will
work
properly
when
connected
to a
RLL
controller. RLL
encoding
by
nature
requires
drive
circuitry
that
can
handle
a
wider
frequency
range
than
MFM drives
have
been
designed
for. If
using
an
RLL
controller
it
is
always
best
to
stay
With
an
RLL
certified drive.
This
will
minimize
the
chances
of
data
loss.
The
compatibility
of
the
controller
to
the
computer
largely
depend
on
whether
both
the
controller
and
the
computer
adhere
to
industry
standards.
If
either
the
controller
or
the
computer
deviate
from
the
standards
there
is
a
potential
for
incompatibility.
Controller
to
computer
compatibility
questions
should
be
directed
to
the
controller
manufacturer
and/or
computer
manufacturer.
ESDI
The
ESDI
(Enhanced
Small
Device Interface)
is
as
its
name
implies
an
enhanced
interface.
This
interface
has
been
around
for a
shorter
period
than
the
ST506/ST412
and
there
are
still
new
features
being
designed
in.
It
is
a
substantial
upgrade
of
the
ST506/ST412
interface.
This
interface
is
oriented
toward
high-capacity,
high-speed
small
Winchesters.
It
is
also
capable
of
handling
magnetic
tapes
and
optical
disk"
drives.
The
ESDI is
designed
around
a
serial
transfer
rate
of
10
and
15
megabit
per
second.
This
interface
puts
more
logic
on
the
drive
and
allows
the
controller
to
be
simplified.
The
compatibility
issues
are
almost
the
same
as
the
ST506/ST412
interface.
One
new
issue
is
interface
speed.
ESDI
drives
and
controllers
are
aVailable
in
10
and
15
megabit
per
second
versions.
The
controller
speed
has
to
match
the
drive
speed.
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