[Coco] Re: Re: Re: Disk Basic and 512 byte block floppies.

[Gene Heskett]

On Tuesday 20 January 2004 06:59, Amardeep S Chana wrote:
>"Gene Heskett" <gene.heskett at verizon.net> wrote

>> Well, as the box said, needs windows 98 or better, so I installed
>> linux.
>>
>> :-)
>
>No argument here!
>
>> The funnier part is that when I found out that the superio chipset
>> on this mobo was capable of any format you could dream up,
>> apparently even including the original apples 128 byte sectors, or
>> even 1024 byte sectors if you needed it, it was a piece of cake to
>> add the 256 byte sector formats to the linux floppy drivers
>> abilities.
>
>No, not the Apple format.  They never had 128 bytes sectors.  They
> were always 256 bytes and in Group Code Recording format.  13 or 16
> per track depending on DOS version.  Floppy disk controllers can't
> make heads nor tails of that bit stream... it's as different from
> FM and MFM as anything could possibly get.  There is a 6502 routine
> that encodes and decodes data buffers to and from a raw sector
> pattern.  It is then written/read at precise software-timed
> intervals one byte at a time to a parallel/serial circuit that
> actually twiddles or reads the head signal.  Cheap but effective
> (and SLOW).
>
>Amardeep

Ok, when I saw the 128 byte sector as a posible option, I assumed 
(theres that word again) that it was an apple format.  My bad.  There 
are all sorts of weird formats in the list of possible formats, 90% 
of which I've never come in contact with.  Anyway, there is a file 
someplace on the system, and whose location and name eludes me ATM, 
that one can edit to add the coco formats as this gives them a name 
that you can then preset the driver tow ork with, and such settings 
are valid until that disk is removed, at which point the defaults are 
restored, so one has to do the re-init operation after inserting each 
disk in the drive.

To make it simpler I extended an arrary of disktypes I found in 
floppy.c by 4 more elements, but I've not done enough testing to 
acertain if that makes the coco/os9 format automaticly detectable.

When the 2.6 kernels settle down a bit, say by 2.6.4 or so, I'll 
restest that, and if it works I'll submit a patch to andrew & see if 
I can get it into the kernel srcs for all to use.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty: soap,
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Copyright 2004 by Maurice Eugene Heskett, all rights reserved.