[Coco] high density floppy controller mods

[Mike Pepe]

jdaggett at gate.net wrote:
> Do you have enough time to lay down (36) 256 byte sectors before the 
> index mark comes back around?
> 
> james 
> 

I should. the transfer rate is doubled, the rotational speed is the same.

The only thing I didn't do, which I wasn't sure about, was to modify the 
delay time of the write signal.

The controller has a LS221 one-shot between the controller and the 
drive's write data line. It's set for a pretty short time constant. I 
was going to reduce the time constant by half during HD mode, but I 
tested without it and it seems to work fine. (?)

I'm really not clear as to what the function of that one shot is anyway. 
None of the example circuits using the MB8877A I've seen show it.

I did verify that my HD formatted disks are not readable in LD mode, 
which is a good sign.

If I knew where the dskini routine is, I'd poke it into making 36 sector 
tracks and see if they can be read back.

-Mike