[Coco] NitrOS9 build errors

[Gene Heskett]

On Monday 20 January 2014 18:38:44 Theodore (Alex) Evans did opine:

> On 01/20/2014 03:57 PM, Gene Heskett wrote:
> > No, because the settings for an 80 track, 96 tpi 5.25 disk ARE
> > different than for a 80 track, 135 tpi 3.5" disk even if both are an
> > identical 720k in capacity.
> 
> Yes, the way that has been arbitrarily decided, they are different.
> 
> > In the former case the disk is _double_ track density, and the bit in
> > offset $10 of LSN0 is set accordingly.  In the latter case, that 135
> > is the normal track density, in fact the only known track density for
> > 3.5" disks, so that bit in offset $10 of LSN0 is not set.
> > 
> > So you cannot and must not use a common format for both disks even if
> > the capacity is identical.
> 
> This is exactly why a 720k 3.5" floppy should be set as 96tpi in the
> descriptor even though it is a 135tpi disk.  If there were 160 track
> 3.5" floppies, there would be some reason, but I have never heard of
> such things.  Since I used a common format when I started using 3.5"
> floppies on my CoCo 3 (I used the 80 track descriptor that shipped with
> level 2 at that time) one certainly can.  You may think that it is a bad
> idea, but it is certainly possible to do.

Absolutely Alex.  The main reason for all this PIMA folderol, the ability 
to put a 48 tpi disk in the 96 tpi drive and read it by double stepping the 
drive, giving folks an extra 48 tpi disk drive intended for read-only, was 
a heck of a good idea.  But it falls flat on its face when someone forgets 
and tries to write to that disk, in THAT drive, because the track rewritten 
is not wide enough to erase the whole 48 tpi width track, so you wind up 
with a 48 tpi disk that, because of the data crosstalk the wider heads of a 
48 tpi drive will see, renders that area of the disk unreadable forever.

Robert Gould and I worked out a patch to prevent that write that has not 
been committed that I know of.  That is about the time I blew the SALT in 
my coco3, and although the SALT has now been replaced, I now have a power 
up crash and burn machine, and I have been busy with my local AM 
broadcaster where both of his transmitters gave up, for different reasons, 
in about 2 weeks time.  And it will be about 2 more weeks by the time I 
round up all the near obsolete transistors to fix the night time low power 
box, a 30 yo LPB-60.  The main 1 kw rated Gates is only 60 yo.  And parts 
are easer to get since gates sold several thousand of those over its 20 
some year production run.

To Tormod:

I can send you that patched driver, or Robert can I expect, as I think it 
really belongs in the next release, but this mail server strips 
attachments.  So if you have a PM address that will accept, or at least can 
whitelist gheskett at wdtv.com, I can send that version of rb1773.asm and you 
can commit it.

ISTR I tried to CC: you once, and it bounced.

Cheers, Gene
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