> Personally, I don't see this as much of a selling point for me since it will do next to nothing for the performance of the system over standard PC133 SDRAM since the G4 only has a 133MHz bus.
Don't confuse a PPC mainboard with a classic Amiga: Unlike the CPU in a classic Amiga, a G3/G4 is not connected to main memory. It is connected to the Northbridge via a bus called "Front Side Bus" (FSB). Other components with direct memory access capability (IDE, PCI, AGP) also go through the northbridge. The northbridge connects to memory via the memory bus. That bus and the FSB are unrelated. Different bandwidth, different protocol, even different clock is possible. A fast memory bus - faster than the FSB - obviously has performance benefits for the whole system because the CPU is only one of several Northbridge "customers".
If someone says "the G4 does not support DDR", it actually means that its bandwidth does not reach the bandwidth of DDR-RAM. It's not a statement about compatibility. And it's not an issue of the G4 not understanding the protocol of DDR RAM (it doesn't have to because it is not connected to it).
To the claim that a G4 is suitably served with 133 MHZ SD-RAM: The G4/Altivec bus(-protocol) on the FSB is faster than single data rate SD-RAM133. Even if the CPU was the only component you want to consider, SD-RAM133 after the northbridge already holds up a G4. I recall that for the CPU alone, the upgrade to DDR memory and reduced latency accounts for a 10% improvement. Add to that the benefits of DMA at DDR-RAM-speed and think of a scenario like games, compiling and AV (all saturating the bus with demands from the CPU, the grapics card and the IDE).
Finally, there is the price tag that makes DDR RAM a selling point: the first generation boards with an Arctica northbridge (Pegasos 1, Amiga One) usually require the use of registered SD-RAM. That is not only slower than unregistered SD-RAM, it's also more expensive and difficult to find.
