G3 is the marketing name used by Apple Computer for the 750 microprocessor that is used in Apple's popular iMac and in its Power MacIntosh personal computers. Like other PowerPC microprocessors, the G3 uses reduced instruction-set computing ( RISC ). The G3 and other PowerPC processors were developed jointly by Apple, IBM, and Motorola.
Developed at IBM, RISC is based on studies showing that the simpler computer instruction s are the ones most frequently performed. Traditionally, processors have been designed to accommodate the more complex instructions as well. RISC performs the more complex instructions using combinations of simple instructions. The timing for the processor can then be based on simpler and faster operations, enabling the microprocessor to perform more instructions for a given clock speed . Typically, the PowerPC can perform one instruction for each clock cycle. The PowerPC architecture handles 32-bit instructions.
The G3 (or 750) has an L1 and L2 cache controller built into it and comes in versions with a clock speed up to 266 MHz in the iMac and up to 400 MHz version in the Power Macintosh series. The G3 operates with low power consumption requirements. A 500 MHz version is planned.