the main thing is that the 12F is rated for a maximum clock speed of 16 MHz.
I guess it would've been too easy to call it a 16 F?? 
There is a 16 speed grade too, but it is not rated to operate as low as the Lisa's CPU board clock speed of 5 MHz. (ie. Although both are rated for 16 MHz, 12F and 16 are not strictly the same)
The CMOS variety "68HC000" will run slower, but those are more static sensitive than the older NMOS versions.
