🚀 go-pugleaf

For a 33MHz 68030, there is a minimum clock speed listed for it in
the databooks. I think it's somewhere around 25Mhz for a 33MHz version, but I
don't have my databook handy.

My question is: why is there a minimum?
One possibility I have heard is that the on-chip registers and/or cache
are dynamic in nature, and since the chip is geared for 33MHz, it divides
this down to whatever rate is needed for the refresh circuitry. Therefore,
if you go below the minimum, the refresh rate slows to below the minimum
needed for the refresh.

Now, is there someone out there who knows about this? I'm interested
specifically in the 68xxx CPUs, but any general info would be helpful.
For example:
1. Is the guess I made above accurate, or is there some other reason?
2. If the reason above is correct, does it apply to the registers, the
   cache, or both (or neither?)
3. If it's just a testing parameter, how far could I crank the clock speed
   down? 20Mhz? 16,8,2,1???

Just curious.
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        --John Wittkoski
          University of Michigan
          johnwitt@engin.umich.edu