Re: Smartport driver for superdrive?

[sheldon@atlcom.net (Sheldon Simms)]

In article <55lffj$la@europa.frii.com>, shack@deimos.frii.com (Randy
Shackelford) wrote:

> >The 14 MHz oscillator doesn't mean much - that is just needed because
> >the 14M signal is not available on the slot bus, and the SWIM chip needs
> >a 14 MHz clock to be able to access high density disks.

> Yep I read that the SWIM has to run at 14 MHz so that's why the oscillator
> is there. Wonder how it works in an 8 MHz SE, I don't think you swap any
> oscillator to upgrade an old one.

The SWIM gets a 15.6672 Mhz clock on the SE, which is divided by two to
provide a 7.8336 Mhz clock for the CPU. The same 15.6672 clock is given
to the IWM on older SEs. The Mac Plus provides a 7.8336 Mhz clock to the
IWM. Apparently both chips are capable of being programmed to divide the
clock internally when they are used to access 800kb disks.

-Sheldon

-- 
W. Sheldon Simms III - sheldon@atlcom.net