> Front Side Bus (Processor Interface Bus) frequency on block diagrams
> is 667 MHz for iMac iSight and 600 MHz for older iMacs.

1.6 GHz CPU <-> 533 MHz FSB
1.8 GHz CPU <-> 600 MHz FSB
1.9 GHz CPU <-> 633 MHz FSB
2.0 GHz CPU <-> 667 MHz FSB
2.1 GHz CPU <-> 700 MHz FSB

So FSB clock rate is always ⅓ of CPU clock rate on all G5 iMacs (as was already written), unless the "ratio" has been tampered with.

> Powermac G5 PCI-X have U3
> Powermac G5 PCIe U4 (= IBM CPC945)
> iMac AGP U3 Lite
> iMac iSight some other ;-)

iMac G5 iSight also has U4/CPC945. Besides, U3/U3H/CPC925 is also used in PowerMac G5 AGP ;-)