[Coco] new high density controller

[jdaggett at gate.net]

The 2793 has internal clock divide. This would allow the switch between HD 
and DD drives. It will not allow the  use of 1.2 Meg floppies.

Using the 2797 and an external clock divider will allow use of 360K, 720K, 
1.2 M and 1.44M floppies.

You don't need two contrtoller chips. Yes you still have two adjustment pots.
Once set, they should not require frequent adjustments. The Intel 82077AA 
should be the chip of choice if you desire no adjustments of pots. Though 
major rewrite of the Disk basic is needed to communicate with this chip.

james

On 9 Aug 2006 at 16:44, Mike Pepe wrote:

> Problem with the 2793 is that it's not designed to be switchable between
> the 250k and 500k data rates. It has internal analog circuitry and would
> require some analog ugliness to make it work  as a dual mode controller.
> 
> Since the HD rates are really only useful in OS9 anyway- you'd need a
> driver no matter what. So, I think the 1773/82077 hybrid is the way to go.