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Re: Question about modifying DOS 3.3 or ProDOS



Jayson Smith wrote:
That's what my thought is. Although actually, if DOS reads the track markings and finds out it's not on track 0, wouldn't it just seek back to track 0 anyway? I'd love to know how to do this.
Jayson

This could be done, but DOS doesn't do it this way.  It "buckets"
all persistent I/O errors into the "I don't know anything about the
drive" category.

Making more distinctions would add code that is only used very
occasionally for serious I/O errors--typically a poor tradeoff,
since that space comes out of everyone's usable space.

ProDOS relaxed the space constraints considerably by using the
Language Card area for most of the OS.

"Jerry" <awanderin@yahoo.ca> wrote in message m3y6k76d8b.fsf@yahoo.ca">news:m3y6k76d8b.fsf@yahoo.ca...

"Michael J. Mahon" <mjmahon@aol.com> writes:


Jayson Smith wrote:

Ah. I was just curious. I assume that means there's not a simple
poke I can enter to change the time DOS moves the head in an I/O
error condition? It's not really that I hate the noise, I just think
DOS wastes a lot of time, since in most cases, moving back a few
tracks would result in a valid track, unless the drive door is open,
no disk is inserted, or the disk is damaged or not formatted.
Jayson

You can change the number of tracks that recalibrate seeks back, but
after it's done, DOS expects the drive head to be positioned at track 0,
so there isn't much room to decrease the count.

Perhaps this is an off-the-wall idea: greatly decrease the number of
tracks the recalibrate seek routine uses (say only 8 tracks).  When an
I/O error occurs, and the head is out way past track 8 (e.g. track
29), multiple I/O errors would occur until the disk head was actually
on track zero, but the buzz would only happen after the fourth recal.
Would it be much slower this way?

--
Jerry awanderin at yahoo dot ca

-michael

NadaNet and AppleCrate II: parallel computing for Apple II computers!
Home page: http://home.comcast.net/~mjmahon

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