[Coco] Thought

[Eric J. Rothfus]

> Well I'd like to do it, it's more a matter of getting the time. :(
> I'm currently juggling several arcade/micro/emu projects and get
> very frustrated at the lack of time I get to devote to each.

Don't I know it.

> It's been a *long* time since I looked at the TRS-80 M1/3 floppy
> controller hardware but from what little I recall, it wasn't timing
> critical in the sense that the Z80 issues a FDC command and is
> interrupted when the drive/data is ready. If this is true, then I
> can't see (in the 5 mins of analysis I've done in my head) that
> 'hiccups' in the USB stream would be a problem? Maybe I'm wrong, but
> it'll all come out in the wash.

The hiccups that are problematic would be those within a sector.
That is, as the data is being shifted out to the FDC, it samples
during a fixed interval, that is sensitive to timing.  Given USB,
however, I'm fairly confident that a hiccup can be avoided within
the data.  It really depends upon the size of the USB transfer.
Hiccups between sectors should be manageable, as well as those
during head-moves.

However, all of these hiccups add up, and as the signals being
generated on the floppy cable deviate from those that an original
floppy would have generated, so does my confidence that floppy
images will work.  Especially those that have been engineered to
depend upon timing or other behaviors of the floppy (copy protected
diskettes).  So my philosophy has been to keep the appearance of
the signals as close to the original floppy as possible.  Probably
overkill...but I'm just doing this for fun anyway.  :-)

> Anyway, very interesting and if I didn't have to work for a living,
> I'd get a lot more of these projects fininshed! ;) If it gets
> anywhere, I'll let you know! Thanks Eric!

:-)