From Newsgroup: comp.sys.cbm

Hi Womo,

Can you explain this swapped SideIDs aspect a bit more or point me to
more info?

Mike G

On Mon, 30 Jun 2003 23:08:34 +0200, Wolfgang Moser <wnah@d81.de>
wrote:

These SideIDs in the headers of each
sector are the real difference betweeen CBM formatted disks
and IBM formatted disks. If Commodore would have used a
format without these swapped SideIDs, then we all could read
and write these disks with the standard BIOS routines. But
they didn't and therefore I needed to program the floppy
disk controller directly.

Womo

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From Newsgroup: comp.sys.cbm

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Hello Mike,


mg@here.com wrote:

Hi Womo,

Can you explain this swapped SideIDs aspect a bit more or point me to
more info?

please have a look in some dodumentation about common MFM
recording format. Maybe you also look for the IBM System 34
format specifications. You'll surely recognize, that every
MFM sector got an associated header field, where some
parameters are stored (Cylinder number, Head number, Size
of the Sector, ...).
Get 1581-Copy from http://d81.de and have a look into the
source code file FDCLOWLV.H . It's header comment contains
many URLs to various documentation. Look out especially for
the intel datasheets.

IBM PC compatible MFM formats always store a "0" into the
head number field, if the disk side is accessed by head 0
and a "1" if a disk sector is read/written by head 1.
Commodore did it the inverse way.


Womo



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From Newsgroup: comp.sys.cbm

Wolfgang Moser wrote:

Can you explain this swapped SideIDs aspect a bit more or point me to
more info?

[...]

IBM PC compatible MFM formats always store a "0" into the
head number field, if the disk side is accessed by head 0
and a "1" if a disk sector is read/written by head 1.
Commodore did it the inverse way.

huh, I suppose we don't really know who did it the "inverse way". It
simply depends on which head you start numbering from ;-) I remember I
saw a lot of 3.5" floppy drives' insides some years ago and I remember wondering about the inconsistencies with the numbering even on their
PCBs connectors...

P.S. It's just for this tiny, puritanic bit of my soul, which wouldn't
rest in peace if I haven't written this. :-)

--
The nice thing about standards is that there are so many of them to
choose from!

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From Newsgroup: comp.sys.cbm

Hi Patryk, you wrote:

Wolfgang Moser wrote:

IBM PC compatible MFM formats always store a "0" into the
head number field, if the disk side is accessed by head 0
and a "1" if a disk sector is read/written by head 1.
Commodore did it the inverse way.

huh, I suppose we don't really know who did it the "inverse way". It

Oh yes, sure, it all depends on some definitions in the
specifications. While IBM specified the System 34 recording
format, Commodore may have done another one. It may possible
also, that the right view depends on the controller hardware:
NEC µPD765 and compatibles against WD1770 and it's compatible
controllers.
Because _my_ personal view (for 1581-Copy) is the PC's floppy
disk controller, which is a extended µPD765 compatible FDC,
I call "side 0", what the controller tells me beeing side 0.
Well, with the high level API of 1581-Copy I changed the view
from the IBM one to the CBM one.
Womo
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