Re: 68882 FPU (was: 68k support status page)

>>> Does anyone knows if I have to limit myself to a 16MHz FPU? Would
>>> a 25 or 33MHz automatically step back to 16MHz and do the job right?
>>
>> Yes, they should work.  Those ratings are the fastest recommended 
>> speed
>> for the chip (i.e. a "not to exceed speed").  Since the clock is
>> external to the chip (i.e. comes off the logic board), the chip will
>> automatically run at the slower (correct) speed.
>
> Many told me that it should. Of course, I'd rather have "I do it
> all the time" answers but I guess it will have to do.
>
> The closest I come to an answer is a BR509_REV3 archived pdf on the
> Motorola site that has some indication (p17) that it might not be
> wise to downgrade the clock too slow. But I could be wrong.

The chart at the top of p17 clearly states that frequency of operation 
of the 33.33 MHz chip is from 16.7-33.33 MHz, and the 25 MHz is 12.5-25 
MHz.  A 16, 25 or 33 MHz chip should work at 16.7 MHz clock speed 
according to Motorola's own specs.  In practice, you can often get away 
with running parts outside of the spec'd range.  Usually, folks want to 
run chips at frequencies in excess of the maximum (e.g. over-clocking a 
CPU).  And one can usually (but not always) get away with this.  
Under-clocking is rarely ever a problem.  Indeed, sometimes chips with 
different clock speeds are manufactured exactly identically, the only 
difference being that certain batches had higher yields which passed 
testing at the higher clock rates.

It should work.  I wouldn't worry about it.  But nothing is ever 100% 
certain.  Not even if a chip is labeled at a given clock rate.
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     My own luck has been curious all my literary life;
     I never could tell a lie that anyone would doubt,
     nor a truth that anybody would believe.

               --  Mark Twain (Following the Equator, 1897)
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