Technical information

CHAPTER 2
Architecture
24 Processor Module
The G3 microprocessor in the PowerBook G3 Series 1999 computer runs at a
clock speed of 333 or 400 MHz. Table 2-1 shows how the speeds of the CPU
clock, the backside cache, and the main memory bus are related.
The PowerPC G3 family of microprocessors includes the PowerPC 740
™
and
the PowerPC 750
™
; the PowerBook G3 Series computers use the PowerPC 750.
Backside Cache 2
The controller and the tag storage for the backside cache are built into the
microprocessor chip. The cache controller includes bus management and
control hardware that allows the cache to run at an independent sub-multiple of
the processor’s clock speed, rather than at the slower clock speed of the main
system bus. In the new PowerBook G3 Series computer, the ratio of the
microprocessor and backside cache clock speeds is 5:2.
The data storage for the backside L2 cache consists of either 512 KB or 1 MB of
fast static RAM on the processor module.
Bus Clock Speeds 2
Table 2-1 shows the clock speeds for the microprocessor, the backside cache,
and the main buses.
Memory Controller and PCI Bridge 2
The memory controller and PCI bus bridge IC is a Motorola MPC106, also
called Grackle. The Grackle IC provides the bus bridge between the processor
bus used on the processor module and the PCI bus used for the I/O controllers
Table 2-1 Clock speeds
Bus or device
Clock speeds (MHz)
G3 microprocessor 333 400
Backside L2 cache 133 160
System bus 66.7 66.7
PCI bus 33.3 33.3