30 Jul
2021
30 Jul
'21
6:20 p.m.
Same here.
I've spent many happy hours in 'the good old days' adjusting
'interleave'
of ST512/406 MFM hard disks to find the optimum setting for a particular
system/controller but had never even heard the term 'skew' until 5 or 6
years ago while playing with odd format diskettes, and then it was in the
track offset sense.
So I was surprised that some folks in the S100/CPM world use 'skew' in the
interleave sense, apparently because the CP/M documentation used it that
way. I'm always surprised how a field so dependent on rigid logical
concepts and definitions has so many inconsistencies.
Thanks everyone!
m
On Fri, Jul 30, 2021 at 8:47 PM Paul Koning <paulkoning at comcast.net> wrote:
On Jul 30, 2021, at 5:35 PM, Mike Stein via
cctalk <
cctalk at classiccmp.org> wrote:
There's a small discussion on S100computers about the terms 'skew' and
'interleave'.
In CP/M documentation 'skew' refers to what's usually called interleave
these days, i.e. offsetting sectors on a track to compensate for the fact
that by the time the computer has processed a given sector the next one
has
already passed by, so that the computer has to
wait an entire revolution
for it to pass by the head again; in other documentation as in Chuck's
22disk for example this is also called 'interleave'.
However, in later documentation the meaning of 'skew' seems to have
changed
to refer to the offset of sectors between
adjacent tracks to compensate
for
the time required to step the head.
I've only ever seen the term "skew" with that second meaning. The first
thing you mentioned in my experience is always called "interleave". For
example, the DEC RX50 has 2:1 interleave and 3 sector skew.
Interleave is normally written as the physical sector number difference of
two logically adjacent sectors (so 2:1 means there is one other sector
between logical sector 0 and logical sector 1). In one place (David
Gesswein's MFM emulator) I've seen it used the other way around, n:1
meaning that logical sector n is physically immediately after logical
sector 0.
paul