Re: Apple2 disk controller questions

[david@uow.edu.au (David Wilson)]

dempson@actrix.gen.nz (David Empson) writes:
>Allow me to step up on the soapbox for a few minutes.

>First: rotation speed and capacity issues.

First, thank you for your extremely good description of disk formats.
You saved me the trouble of researching the numbers an posting my own
(less detailed) report.

>(An aside: the high density 5.25" drive doubles the track density as
>well as almost doubling the number of bits that can be recorded per
>track.  The high density 3.5" drive has the same track density as the
>double density drive, probably to allow better compatibility with double
>density media than you typically get with 5.25" drives.)

High Density (1.2MB) 5.25" disks are a little different. They run at 500kb/s
and at 360 rpm (which incidently is the rotation speed of 8" floppies).
The PC/AT could read DD disks in its HD drive by changing the data rate to
300kb/s

Here is a table of floppy disk formats I have built up over the years
(I must add 21MB and 120MB floptical drives and Sony's HiFD drive soon):


disk	speed		data rate	trk	sector	trk/hd
size	rpm	s/rev	kb/s	scheme	kb	cnt*sz	count	KB
--------------------------------------------------------------------------------
8"	360	0.167	500	FM	41.67	26*128	77/1	260	SSSD (8)
8"	360	0.167	500	FM	41.67	26*128	77/2	520	DSSD (8)

8"	360	0.167	500	MFM	83.33	26*256	77/1	520	SSDD (9)
8"	360	0.167	500	MFM	83.33	26*256	77/2	1040	DSDD (9)

5.25"	300	0.200	250	FM	25.00	8*256	40/1	80	SSSD
5.25"	300	0.200	250	FM	25.00	8*256	40/2	160	DSSD

5.25"	300	0.200	245	GCR	49.00	16*256	35/1	140	SSDD (1)
5.25"	300	0.200	250	MFM	50.00	8*512	40/1	160	SSDD (3)
5.25"	300	0.200	250	MFM	50.00	9*512	40/1	180	SSDD (3)
5.25"	300	0.200	250	MFM	50.00	8*512	40/2	320	DSDD (3)
5.25"	300	0.200	250	MFM	50.00	9*512	40/2	360	DSDD (3)
5.25"	300	0.200	250	MFM	50.00	9*512	80/2	720	DSDD

5.25"	360	0.200	300	MFM	50.00	9*512	40/2	360	DSDD (4)
5.25"	360	0.200	300	MFM	50.00	9*512	80/2	720	DSDD

5.25"	360	0.167	500	MFM	83.33	15*512	80/2	1200	DSHD (4)

3.5"	300	0.167	250	MFM	50.00	9*512	80/2	720	DSDD (5)
3.5"	300	0.167	250	MFM	50.00	5*1024	80/2	800	DSDD (2)
3.5"	var	var	var	GCR	var	var*512	80/2	800	DSDD (7)

3.5"	300	0.167	500	MFM	100.00	18*512	80/2	1440	DSHD (6)
3.5"	var	var	var	GCR	var	var*512	80/2	1600	DSHD (A)

3.5"	300	0.167	1000	MFM	200.00	36*512	80/2	2880	DSED

(1)	Apple ][
(2)	Applix
(3)	IBM PC
(4)	IBM PC/AT
(5)	IBM PS/2 25,30
(6)	IBM PS/2 > 30
(7)	Macintosh & Apple //
(8)	IBM 3740
(9)	IBM System 34
(A)	AE 1.6MB drive on Apple //

IBM System 34 format 256 byte sectors

	12 * 00
	3 * F5
	1 * FE
	1 * Track#
	1 * Side#
	1 * Sector#
	1 * SecLen
	2 * CRC
	22 * 4E
	12 * 00
	3 * F5
	1 * FB
	256 * data
	2 * CRC
	54 * 4E
	------
	372 bytes = 2976 bits
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia  david@uow.edu.au