model 720 comparison

We currently have two model 720s in the computer room.  Old 720 is feature
#2061 and batch cpw of 240.  New 720 is feature #2062 and batch cpw of 420.
Both systems have similar dasd.

The cpw numbers predict that New 720 will run 80% faster than Old 720.  But
running a CL pgm that counts to 50 million on each system gives the
following results:
    OLD count to 50 million - 28 seconds
    NEW count to 50 million - 24 seconds.

Same numbers in batch or interactive. And NEW 720 has nothing running on it
right now.

Now New 720 IS much faster in real time than Old 720.  Dayend runs a lot
faster. And because of the way things are done here we have had to migrate
back and forth between the two system twice already.  The scratch install,
mirror the drives, load all libraries that has been run on both systems ran
a lot faster on New 720.

Any idea where New 720 gets its quicker speed from ?  The cpu only looks to
be 20% faster, dasd is the same, yet in practice it does run at least 50%
faster than Old 720.

thanks,

Steve Richter