1.44M floppy on Color Computer (was Re: Ebay reaches new low)

From: Dwight Elvey <elvey_at_hal.com>
Date: Wed Nov 10 18:08:45 1999

"Sean 'Captain Napalm' Conner" <spc_at_armigeron.com> wrote:
> If the direct addressing mode is used for instructions one and three, you
> get 4 cycles each, 5 for extended (16 bit) addressing. So this sequence
> (depending upon the addressing mode used) will take 17 to 19 cycles per byte
> to run (excluding wait states).

 Another factor, the sectors for DOS formatted disk are
512 bytes long. Any loop that only does 256 won't make it.
It would need to be formatted with more wasteful 256 byte
sectors. This has been a good line of thought ;)
 One of the other things I remember about these controllers
is that at 32us, you need to read the data byte within
27us of DRQ. I would think that this would hold for
13.5us for a 16us transfer. It truely doesn't look like
there is a way to do it with anything but DMA.
 Here is another idea that I fling like a monkey at the zoo.
Use a small PIC chip to read the 1.44 disk. Have a small
disk cache RAM to hold a buffer ( Not a lot of hardware,
so far ). Connect the unit to the CoCo, how ever one would
like. Even emulating the original controller so no
software needs to be modified, just the effective size
of the physical disk ( or map as multiple disk ).
Received on Wed Nov 10 1999 - 18:08:45 GMT

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