🚀 go-pugleaf

As the title suggest, I am wondering if there is a standard 
for 3 1/2 inch floppy formats. I am about to start using a 
3 1/2 floppy on our new machines, and I get to decide what 
format we will use. Since we have never had 3 1/2 inch drives 
before, I have no constraints to be compatible with any of 
Terak's past products.

I am interested in being compatible with some standard that exists
or is emerging.

The drives we are using are TEAC 35F, which are double sided double
density, 80 cylinders.

The format I was planing on using, and of course I would change if
some one has a better idea, is based on IBM 3740, and is as follows:

	Side 0, Cylinder 0 would be FM. Sector 7 of this track would
	be used for identifying the media characteristics. The rest
	of the track would be availible for use. This track would not 
	be visible to the OS, (in our case UNIX) through the normal 
	read/write command, but would be accessed through ioctl calls.


	Density	| Recording | Bytes/ | Sectors/	| capacity
		| mode	    | sector | Track	| in Kbytes
	--------+-----------+--------+----------+----------
	SSSD	| FM	    | 128    |	16	| 158
	--------+-----------+--------+----------+----------
	SSDD	| FM (trk 0)| 128    |  16      |
		| MFM (rest)| 256    |  16      | 316
	--------+-----------+--------+----------+----------
	DSDD	| FM (trk 0 | 128    |  16      |
		|    side 0)|        |          |    
		| MFM (rest)| 256    |  16      | 636
	--------+-----------+--------+----------+----------
	SSSD=Single Sided Single Density
	SSDD=Single Sided Double Density
	DSDD=Double Sided Double Density


An alternative scheme that I am considering is as follows:


	Density	| Recording | Bytes/ | Sectors/	| capacity
		| mode	    | sector | Track	| in Kbytes
	--------+-----------+--------+----------+----------
	SSSD	| FM	    | 128    |	16	| 160
	--------+-----------+--------+----------+----------
	SSDD	| MFM       | 512    |  8       | 320
	--------+-----------+--------+----------+----------
	DSDD	| MFM       | 512    |  8       | 640
	--------+-----------+--------+----------+----------

As to the interleave factor, I am still playing with that to
try and determine a good value for it. The two candidates that
I have in mind are 
	1. no interleave, for simplicity.
	2. same as DEC RX01

Ofcourse one can not talk about 3 1/2 floppies with out thinking
of the MAC. I have been told that they are single sided only and
they rotate at a different speed (compared to the TEAC drives)

To conclude, I would be interested in hearing from people on the
subject of 3 1/2 floppy format being used today, as well as comments
on the two formats listed above. I will ofcourse post a summary if
there is much interest

sohail
-- 
Sohail Hussain

uucp:	 ...{decvax,hao,ihnp4,seismo}!noao!terak!sohail
phone:	 602 998 4800
us mail: Terak Corporation, 14151 N 76th street, Scottsdale, AZ 85260