there is allot of misinformation here so i'll set everything straight, if you disagree do the research and you will find i am right.
the MDD G4 used a 1400MHz (some say overclocked 20MHz but seriously who cares) 7455 G4 chip from motorola it's written on the die in gold ink.
Motorola from the introduction of the G4+ made two versions of the G4+ one with the extra pins for L3 cache another without the 7450 and the 7440, this carried on to be the same with the 7455 and the 7445 and again with the 7447 and the 7457, they are other than the extra pins exactly the same and pin compatible the 745x chips can be used without L3 cache as they were in some emacs, the last apple computer to support L3 cache was the mdd g4, now after that apple either used 7455's with no L3 cache or 7445's and latter on 7447's 7447A's and in the mac mini and current powerbooks the 7447B, apple has never and will never used the 7457, only a few upgrade manufactures did and they alone are not push enough for motorola to develop the chip so motorola dropped the 745x chips and now only develops the 744x chips in use by apple today.
oh and dude above use the powerlogix cache ratio utility to push the cache ratio up so the cache stays at the same speed but the cpu speed can increase, it's on a multiple much like the cpu is on the fsb.