[sebhc] h17 and h8d disk images

[Barry Watzman]

That's the 2nd way ("but to do the interleaving when the disk is formatted")

It's possible, also, to do both (use the sectors out-of-sequence, and also
format them (put them on the disk) out of sequence).


-----Original Message-----
From: sebhc at sebhc.org [mailto:sebhc at sebhc.org] On Behalf Of Steve Thatcher
Sent: Wednesday, September 01, 2004 8:26 PM
To: sebhc at sebhc.org; sebhc at sebhc.org
Subject: RE: [sebhc] h17 and h8d disk images

make that three ways because I have had cp/m systems that interleaved the 
sector on the disk on the physical media.
The floppy controller could care less when the track is formatted as to 
which sector was which on a soft sector disk.

best regards, Steve Thatcher

At 07:45 PM 09/01/2004 -0400, Barry Watzman wrote:

>There are two ways to interleave.
>
>In the 1st method, used by CP/M, you have an interleave table in the
>operating system itself.  The sectors are in physical order on the
diskette,
>but are not used in physical sequence.  That is, CP/M (on an 8" disk) uses
>sector 1 then 7 then 13, then 19, etc.
>
>The other way is to have the OS use the sectors sequentially (1,2,3 etc.)
>but to do the interleaving when the disk is formatted.  So the OS will ask
>for sector 1, 2, 3 ...., but on the disk the sector after sector 1 is not 2
>but rather something else.  There is no requirement that the sectors on the
>disk be in sequential order.  In fact, there is no requirement that they be
>contiguous, or that they be "positive" numbers (if one wants to interpret
>them as signed numbers).  They are more like labels than actual numbers,
>they can be in any sequence, and there can be gaps (a fact on which may
copy
>protection schemes rely).
>
>
>
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