_______________________________
                     |                               |
                     |           APPENDIX C          |
                     |                               |
                     |     ABOUT DISK INTERLEAVE     |
                     |_______________________________|  


The disk interleave means the way the sectors are written to the disk to get the
maximum disk access speed.  For all physical drives, there is an interleave (3.5
disk, 5.25 floppy, hard disk).

In D.D.DeLuxe, if you are using an Apple //gs and a 3.5 drive (800k or 1.44m),
you can specify the interleave value.  Most disk utility program today use a
fixed interleave (interleave 4 for 3.5 disk) when you ask to format a disk.
With D.D.DeLuxe, you can specify you own to get the maximum disk access speed
(both write and read).

The rule is:  the higher the interleave, the more time it take to access the
disk (both read and write).

The ideal is an interleave of 1 for all type of disk, but the disk controller
and/or the computer and/or the operating system are too slow to handle the data
transfer (the drive can, but not the computer or controller or the operating
system).  It is why we must put an interleave; it's to slow down the data
transfer between the drive and the computer/controller/operating system.

On an Apple //gs, when you format a 3.5 disk, use the following interleave:

     - Prodos 8 application:   interleave 3
     - Prodos 16 application:  interleave 4
     - GS/OS application:      interleave 2

Use exactly these interleaves to get the maximum disk access speed.  You can
use other interleave than these one if you wish (it will work), but it will
slow down the disk access (read and write).

When a new faster Apple //gs (more than 2.8 MHz) will be available, you will be
able to use an interleave of 1 (the fastest disk access) for 3.5 disk.

If you have an disk program that uses Prodos 16 but you intend to boot the
program with GS/OS, it's preferable to format the disk with an interleave of 2
to get the maximum disk access.



                   <<<< Written by Louis Roy, 1989 >>>>


This documentation come from the D.D.DeLuxe V5.0 documentation, appendice C.