755cd pentium upgrade

[<scott.newman@fulcrum.com>]

     I have a non-new 755cd (100MHz 486DX4).  I am planning to do the 
     Pentium upgrade for it.  If I understand correctly, the upgrade is to 
     a 75MHz Pentium.
     
     I though that a 100MHz DX4 system had a clock rate of 33MHz.  In order 
     to run a 75MHz Pentium, doesn't this mean that the system clock has to 
     be changed to 25MHz?  If this is the case, won't the reduced system 
     clock speed slow down other aspects of the system, like disk and video 
     throughput.
     
     Is the Pentium upgrade really an improvement?
     
     Scott