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Figure 2-1 is a simplified block diagram of the iBook computer. The diagram shows the main ICs and the buses that connect them together.
The architecture of the iBook is designed around the PowerPC G3 microprocessor and two new custom ICs: the Uni-N memory controller and bus bridge, and the KeyLargo I/O device controller. The microprocessor and the two custom ICs occupy the center of the block diagram.
The PowerPC G3 microprocessor is connected to the Uni-N memory controller and bus bridge IC by a 60x bus with 64 data lines and a bus clock speed of 66 MHz. The Uni-N IC has other buses that connect with the KeyLargo IC, the main system RAM, the graphics IC, and the Ethernet PHY IC. The buses implemented by the Uni-N IC are summarized in Table 2-2, which is in the section Memory Controller and Bus Bridge.
The Uni-N IC is connected to the KeyLargo I/O controller IC by a 32-bit PCI bus that has a bus clock speed of 33 MHz. That PCI bus also connects to the Boot ROM. The KeyLargo IC has other buses that connect with the hard disk drive, the power controller (PMU99), the sound IC, the internal modem, the CD-ROM drive, and the optional wireless LAN module.
