as i have seen, things are like this,
020 and 030 are the same speed as it comes to mhz per mhz, ofcourse there are 030's with more Mhz than 020's
040 is 4x faster than 030 in the same Mhz
a 040@25 is twice faster than 030@50
060 is about 2x than 040 in the same mhz because of the superscalar.
so 040 WAS a BIG progress!