31 Jan
2012
31 Jan
'12
11:43 a.m.
On Tue, Jan 31, 2012 at 1:42 PM, Fred Cisin <cisin at xenosoft.com> wrote:
Doh! Too many years since I was grubbing around at that level
(following too many years of deep grubbing on 4040s and 1541s).
On Mon, 30 Jan
2012, Ethan Dicks wrote:
On Tue, 31 Jan 2012, Christian Corti wrote:
> s/GCR/MFM/g
> GCR was almost never used on the Amiga. The Amiga does an entire track of raw data to and
from GCR in memory
[...] Thus supporting my contention of an instance of MFM
without DAMs.
(FM/MFM and DAMs are both essential components of the "IBM"/WD track
format "standard", but are largely independent of each other - Amiga being
an example of MFM without the IBM/WD track structure.)
Yes. If you were to magnaflux an IBM/WD diskette, it would look
radically different (pun intended) from an Amiga diskette, the biggest
visible difference being individual sectors with variable gaps vs
jammed-together sectors with a variable-length tail. The consequence
of such is that the Amiga doesn't have to look for the start of a
sector when reading - it just opens the gates, slurps up slightly more
than one turn of the medium and figures out what's what in software.
Depending on how you define GCR, it can easily be
argued that MFM
IS A TYPE OF GCR. ?Ethan is therefore not WRONG.
Thanks for defending me, but I mis-remembered. CBM disks use a
recognizable GCR, and Amiga floppies use an MFM scheme. The rest
should be accurate (sectors are adjacent without variable intersector
gaps, and the blitter engine is used to convert to/from binary buffers
in CHIPMEM)
-ethan