XCPU

XCPU

File:X02046-008.jpg The original XCPU, Waternoose
Introduced	Late 2005
Designed By	IBM Microsoft
Codename	Xenon
Type	CPU
Used In	Original Xbox 360
Clock Speed	3.2GHz
Cache	L1: 32KB/32KB L2: 1MB
Instruction Set	PowerPC RISC
Cores	3
Threads	6
Predecessor	Shiva
Successor	XCGPU

The Microsoft XCPU, codenamed Xenon, is the central processor used in the Xbox 360. It is designed to be used with the ATi Xenos graphics chip, which also functions as the northbridge and memory controller.

The processor was developed by Microsoft and IBM, and the first version was codenamed Waternoose after the fictional character Henry J. Waternoose III.

Specifications

• 3 two-way SMD-capable RISC cores clocked at 3.2GHz
• SIMD: Two VMX128 units
• 32KB L1 data cache
• 32KB L1 instruction cache
• 1MB L2 cache at 1.6 GHz with a 256-bit bus
• 21.6GB/s FSB
• 768 bits of IBM eFUSE One-Time-Program memory for fusesets
• One-Time-Programmable ROM and 64KB SRAM for the 1BL and Config Ring
• Big-endian architecture

Versions

Waternoose (90nm)

Main article: Waternoose (CPU)

The initial version of the XCPU, named Waternoose, entered production in 2005 and is used on the Xenon and Zephyr motherboards. It is notable for being quite power hungry.

Loki (65nm)

Main article: Loki (CPU)

In 2007, the XCPU was shrunk and slightly redesigned for the 65nm process. Named Loki, it is used on the Falcon and Jasper motherboards. It is notable for having significantly lower power and thermal requirements.

XCGPU

Main article: XCGPU

In 2010, the XCPU was shrunk to the 45nm process and combined with the Xenos graphics chip to create a system-on-a-chip, called the XCGPU.