[G4] "grackle"? grumble, grumble...

[brad powell]

I have a Power Mac G4 ("Sawtooth"), w/400 Mhz CPU,1.25
GB RAM and 
OS 10.4.11
 
  Until this past week I didn't think I could
significantly upgrade to a dual processor.  I just
learned that my motherboard has Uni-North
ASIC chipset/version 7.   So although I'm excited now
about the low price of dual 533mhz cpu's on ebay,  I
also read:

 "G4’s Motorola XPC106 “Grackle” PCI/Memory controller

prevented the G4 from hitting speeds higher than 500
MHz."

 Does this mean that I need to limit a processor
upgrade to
 dual 450,466 or 500mhz CPU?

 Is there some workaround to the  "Grackle"
controller,
to fully utilize a dual 533 mhz cpu or faster?  All my
googling brings me back to the same article in
LowendMac.

thanks
brad