[Coco] HD floppy controller update: success!
jcewy at swbell.net
Sat Jul 5 12:35:45 EDT 2008
Hey Chuck, this is good stuff you're working on.
IMHO, I think a High Density CoCo OS-9 disk should be formatted the same
as an MM/1 HD floppy. The MM/1 uses the WD37C65, and 33 256-byte
sectors per track. I don't have any info immediately at hand about gap
length. In the MM/1 technical manual the "rates" parameter to dmode is
$10. Perhaps this is passed directly to the FDC, and the 37C65
datasheet might give more specific info.
If you do decide to manufacture some boards, my temptation level would
go sky high. Cost would be a factor for me. PCB only option would be
cool. But I may have to download Eagle and see if I can fab a
double-sided board. I have a homebrew CNC drill that I've done far too
little with so far. I wonder where I can get ahold of the 82077AA.
Chuck Youse wrote:
> So after working pretty much dawn till dusk yesterday, and a couple more
> hours this morning, I've proven that the CoCo 3 at 1.78MHz can indeed
> read high-density floppies with the 82077AA-1! No HALT required! I've
> successfully read sectors from all parts of a PC-formatted disk (and
> verified the data).
> Of course, for the Coco 256-byte sectors are MUCH preferred; ideally 36
> 256-byte sectors per track. Has anyone ever heard of such a format? I
> could use some gap length hints. Also, does anyone know how I might
> format such a disk under Linux? setfdprm/fdformat doesn't seem to do
> the trick (fdformat ignores the setfdprm parameters... dumb)
> Coco mailing list
> Coco at maltedmedia.com
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