>> ?  so 5000/200 is 25MHz bus, clock-doubled to 50MHz in CPU, and 5000/240
>> is 40MHz bus, clock-doubled to 80MHz in CPU?
>
> No, the /200 and /240 are R3000 machines, not R4000 machines.  These
> really are 25MHz and 40MHz CPU cores respectively.

TURBOchannel is driven independent from CPU clock source.  3MIN/MAXINE
and 3MAX+ are designed to decouple CPU module and rest of system.
That enabled, for example, 3MIN/MAXINE to have 20MHz/25MHz/33MHz R3000
or R4000 module in popoff-popin fashion.

Tohru Nishimura