CMOS for NMOS

[Chuck Guzis]

On 04/15/2018 05:08 PM, allison via cctalk wrote:
> On 04/15/2018 10:25 AM, David Griffith via cctalk wrote:
>>
>> I'm pondering upgrading the CPU of a Pacccomm Tiny-2 Mk2 radio packet
>> controller from a 6Mhz Z80 processor and SIO to 10Mhz parts.  My
>> problem is that the parts already in it appear to be NMOS.  The family
>> is still being made by Zilog, but for 10Mhz parts, CMOS is all they
>> have.  Can I just drop in CMOS, change out the crystal/oscillator and
>> have things work as expected?
>>
> No, and why?
> 
> Changing to CMOS can cut power drain.  However speeding up clocks can
> make the packet controller
> broken even if it runs!  If you keep the 6mhz clock all will be fine.

Quite correct, Allison.  I confined my answer to "Can I drop a CMOS Z80
into an NMOS Z80 socket?"

And in particular, why not run the 10MHz part at the original 4MHz or
whatever?  A 10MHz part doesn't mean that it has to run at 10MHz.

As to the rest of the question, I confess that I was blind.

--Chuck