Editing Power Mac G4 (section)

== Mirrored Drive Doors ==
The last G4 towers take DDR memory: PC2100 in 133 MHz machines and PC2700 in 167 MHz machines. PC2100 memory in a 167 MHz machine stops it booting with a single tone and a flashing front light. They hold four hard drives in two carriers, with the 100 MHz ATA cable in the rear carrier and the 66 MHz cable in the front, which Apple says must not be swapped.<ref name="mdd" /> Apple also notes that several bus-powered FireWire devices with an Apple ADC 17-inch CRT display can exceed the supply's capacity and shut the system down (p. 112).<ref name="mdd" /> The supply connector and test points are tabulated on [[Power Mac G4 (Mirrored Drive Doors) Service Source]].