Microprocessor and Cache

The microprocessor communicates with the rest of the system by way of a 66-MHz, 64-bit 60x bus to the Pangea IC. The backside cache is built into the microprocessor.

G3 Microprocessor

The microprocessor used in the iBook is a PowerPC 750CX microprocessor, which is a type of G3 microprocessor. It has several features that contribute to superior performance, including:

on-chip level 1 (L1) caches, 32 KB each for instruction cache and data cache
an on-chip second level (L2) cache consisting of 256 KB with a clock speed ratio of 1:1
a microprocessor core optimized for Mac OS applications

The PowerPC 750CX microprocessor in the iBook normally runs at a clock speed of 500 MHz. The PowerStep feature allows the user to slow the clock speed down to 400 MHz. See PowerStep.

Backside (L2) Cache

The data storage for the L2 cache consists of 256 KB of fast static RAM that is built into the microprocessor chip along with the cache controller. The built-in L2 cache runs at the same clock speed as the microprocessor.