🚀 go-pugleaf

mimperat@cs.dal.ca (Marco Imperatore) writes:

>Hi all.

>I'm trying to program the FDC directly through the I/O ports (0x3f2-0x3f5).
>I think I have some things figured out but there are still a lot of things
>which are unclear.  For instance:
>  1.  Which FDC commands provide an interrupt (IRQ6) when complete?

...lots of fun questions deleted......(brevity)

>As you can see I'm still rather uninformed.  I ordered the Intel Peripherals
>book and it should be here in a few days but I'm not sure if it will contain
>any information on the FDC.

The Intel book is quite good to have anyhow, but you will probably find
that it doesn't do justice to the formatting modes.  What you probably
need is an IBM publication that covers the abstract information about
floppies, since they (or DEC) came up with the idea of a floppy in the
first place.  A good application note from IBM or DEC will explain how
data is written on diskettes, right from the low level (i.e. magnetic
fields) to high level (Dos or equiv. level).

I don't know many answers for you questions, since I haven't had the
need to go so deep into things, but a few things I can answer.  
Numbers of heads, etc. etc. are following (MS-DOS formats assumed)
Form-
atted		Num of	Num of	Sctrs	Bytes
Size		Heads	Tracks	/ Trk	/ Sctr	Normal	Unusual	Obs
160Kb	5.25"	1	40	8	512		X	X
180Kb	5.25"	1	40	9	512	X		X
320Kb	5.25"	2	40	8	512		X	X
360Kb	5.25"	2	40	9	512	X		X
720Kb	3.5"	2	80	9	512	X
1.2M	5.25"	2	80	15	512	X
1.4M	3.5"	2	80	18	512	X

In general, approx. formatted capacity is Heads * Tracks * Sectors *
Bytes-per-sector.

There's one (of the easier) questions answered.  Also, a look at
Norton's Utilities may yield more answers that may be helpful.
Especially Nortons Disk Doctor, Disk statistics option.

Best of luck with the rest of your quest(ions!).

[dav]   aka.
David Emrich
gude@uniwa.uwa.edu.au