11 Jun
2004
11 Jun
'04
11:05 a.m.
The information I have gives the makeup of each of the
gap types in
terms of bit patterns, counts, what clock transitions are missing for
MFM formats etc.
Question is, is this a standard? I mean, for any disk using MFM or FM
recording are these bit patterns going to be the same? Or is it
dependant on the controller chip being used?
It's sort-of a standard for standard controllers (the sort-of because the
WD1771, for example, could read/write a couple of data markers that no
later controller could write -- and the TRS-80 Model 1 used one of
them...). That's why you can read a disk formated on an HP9114 (WD2797
controller IIRC) on a PC (Intel 8272 controller).
However. it's not standard on non-stnadard controllers, meaning DEC M2FM
(RX02), any of the GCR ones (Apple ][, older Macs, Commodore Pet/C64
drives ,etc).
-tony