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Cache Memory

The G4 microprocessor in the configurations with 466 and 533-MHz clocks has an external backside L2 cache. The G4 microprocessor in the configurations with 667 and 733-MHz clocks has an internal L2 cache and an external L3 cache.

Note
The Power Mac G4 computer does not use jumpers to control the clock speeds of the processor and cache.

External Level 2 Cache

The external backside level 2 (L2) cache consists of 1 MB of high-speed SRAM. The speed ratio of the microprocessor and cache is 2:1, as shown in Table 2-1.

Table 2-1 Speed ratio of L2 cache clock

Microprocessor clock frequency	L2 cache clock frequency
466 MHz	233 MHz (2:1 ratio)
533 MHz	267 MHz (2:1 ratio)

External Level 3 Cache

The external backside level 3 (L3) cache consists of 1 MB of high-speed SRAM. The speed ratio of the microprocessor and cache is 3:1, as shown in Table 2-2.

Table 2-2 Speed ratio of L3 cache clock

Microprocessor clock frequency	L3 cache clock frequency
667 MHz	222 MHz (3:1 ratio)
733 MHz	244 MHz (3:1 ratio)