Re: /etc/disktab on vax

On Jul 3, 2012, at 12:06 PM, Dave McGuire <[email protected]> wrote:

> On 07/03/2012 02:54 PM, Mouse wrote:
>>>> IIRC the Z80 required a 4x clock, so a 20MHz Z80 is about as fast as
>>>> a 5MHz 8080 or 8085.
>>> It's not that the Z80 "requires a 4x clock", but four T-states (clock
>>> cycles) make up one machine cycle.  [...]
>> 
>> Also - and this memory is seriously fuzzy, so it could be entirely
>> wrong - I think the 8080 required a two-phase clock, so that there are
>> four, not two, state changes on the clock pins per clock cycle.  This
>> could easily turn into "requires a 4x clock", so if my memory is right
>> and the Z80 copied that particular bit of design....
> 
>  The 8080 does require a two-phase clock, but they're at the same
> frequency, and nonoverlapping, so they're (sorta) easy to generate.  The
> 8224 generates them from a single crystal.
> 
>  You make a good point, but the Z80's clocking subsystem bears no
> resemblance to that of the 8080.

...and WTF does any of this have to do with /etc/disktab on the VAX?

-- thorpej