IBM Xenon microprocessor.

Xenon is a CPU that is used in the Xbox 360 game console. The processor, internally codenamed "Waternoose" by IBM^[1] and "XCPU" by Microsoft, is based on IBM's PowerPC instruction set architecture, consisting of three independent processor cores on a single die. These cores are slightly modified versions of the PPE in the Cell processor which was designed specifically for the PlayStation 3.^[2][3] Each core has two symmetric hardware threads (SMT), for a total of six hardware threads available to games. Each individual core also includes 32 KiB of L1 instruction cache and 32 KiB of L1 data cache.

The processors are labelled "XCPU" on the packaging and are manufactured by Chartered. Chartered reduced the fabrication process in 2007 to 65 nm, thus reducing manufacturing costs for Microsoft.

The name "Xenon" was repurposed from the code name for the Xbox 360 in early development.

[edit] Specifications

• 90 nm process^[4], 65 nm process upgrade in 2007^[5] (codenamed "Falcon")
• 165 million transistors
• Three symmetrical cores, each two way SMT-capable and clocked at 3.2 GHz^[4]
• SIMD: VMX128 with 2× (128×128 bit) register files for each core.^[4]
• 1 MB L2 cache^[4] (lockable by the GPU) running at half-speed (1.6 GHz) with a 256-bit bus
• 51.2 gigabytes per second of L2 memory bandwidth (256 bit × 1600 MHz)
• 21.6 GB/s Front-Side Bus^[4]
• Dot product performance: 9.6 billion per second
• 115.2 GFLOPS theoretical peak performance
• Restricted to In-order code execution^[4]
• eFuse 768 bits^[6].
• ROM (and 64 kbytes SRAM) storing Microsoft's Secure Bootloader, and encryption hypervisor^[6].
• Big endian architecture.

[edit] References

• Xenon hardware overview by Pete Isensee, Development Lead, Xbox Advanced Technology Group, written some time before 23 June 2004

[edit] External links

• Ars Technica explains the Xenon CPU

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