Re: 1571 drive is 2MHz?

wlevak_at_cyberspace.org
Date: 2003-09-19 05:42:36

The major chips are:
6502A
65C22A
8520
6526A

All are 2MHz chips.

The 1571 can run at 2 MHZ (1571 mode) or 1 MHz (1541 mode).  The clock
speed is controlled by the 64H156 at location U6.

On Fri, 19 Sep 2003 jbevren@starbase.globalpc.net wrote:

> I do remember one of the VIA lines (or was it a cia line?) that could switch
> between 1mhz and 2mhz.  Find a ref guide and read up :)
> 
> -David
> 
> On Fri, 19 Sep 2003 ncoplin@orbeng.com wrote:
> 
> > Hi All,
> > 
> > Can someone confirm that the 1571 drive is a 2MHz unit and that the MPU,
> > VIAs and CIA are all rated for 2MHz operation. The VIA chips in my unit are
> > marked 6522P2 rather than 6522A which is what I would have expected....
> > 
> > - Nick
> > 
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