[roders]

I've got the stock 512Mb ram in my 1.8Ghz G5 (in two 256MB pairs) and have been given, and have installed in slots three and four, two sticks of PC2700 Ram (128MB each), my machine works fine, and the total amount of ram is reported correctly (768MB).
ASP reports the Apple Ram as PC3200 and the extra Ram as PC2700, the bus speed is reported as 900Mhz, this shouldn't work should it?

[WizOSX]

If the 1.8 G5 works like G4 Macs then you can certainly do what you are doing (as you already know). It's just that the bus must slow down to the speed of the PC2700 Ram when accessing memory since all RAM must be used at the same speed (the slowest RAM). So your motherboard/bus is still 900mhz, just slowed down regularly.