Re: Disks that boot on 13 and 16 sector ROMs?

[Andy McFadden <fadden@fadden.com>]

Lyrical Nanoha <LyricalNanoha@dosius.net> wrote:
> I've heard of disks that will boot natively on 13 and 16 sector ROMs, how 
> do they pull this off? I'd like to mess around with this ability for the 
> hell of it, now that I've been able to get DOS 3.2 up on my Apple //e 
> (with some help lol).

They added a 6&2-encoded sector 0 to track 0.  If you boot from an old
PROM it reads the DOS 3.2 boot sector, if you boot from the new PROM it
gets the new boot sector.  One of the 5&3-encoded sectors on track 0
becomes unreadable.

If you have a NIB image formatted this way, you can toggle the sector
mode in the CiderPress disk viewer to see both versions.  (I'm told that
the DOS 3.2 boot sector is actually scrambled a bit for some reason;
one of these days I'll implement that.)

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