Neha Patil (Editor)

Xenon (processor)

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Designed by
  
IBM

Instruction set
  
Power Architecture

L1 cache
  
32/32 kB

Common manufacturer(s)
  
IBM, GlobalFoundries

Cores
  
3 cores

L2 cache
  
1024 kB

Xenon (processor)

Microsoft XCPU, codenamed Xenon, is a CPU used in the Xbox 360 game console, to be used with ATI's Xenos graphics chip.

Contents

The processor was developed by Microsoft and IBM under the IBM chip program codenamed "Waternoose", which was named after Henry J. Waternoose III in Monsters, Inc.. The development program was originally announced on 2003-11-03.

The processor is based on IBM PowerPC instruction set architecture. It consists of three independent processor cores on a single die. These cores are slightly modified versions of the PPE in the Cell processor used on the PlayStation 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 XCPU processors are manufactured at IBM's East Fishkill, New York fabrication plant and Chartered Semiconductor Manufacturing (now part of GlobalFoundries) in Singapore. Chartered reduced the fabrication process in 2007 to 65 nm from 90 nm, thus reducing manufacturing costs for Microsoft.

Specifications

  • 90 nm process, 65 nm process upgrade in 2007 (codenamed "Falcon", later "Jasper"), 45 nm process since Xbox 360 S model
  • 165 million transistors
  • Three symmetrical cores, each two way SMT-capable and clocked at 3.2 GHz
  • SIMD: 2xVMX128 with dedicated (128×128 bit) register file for each core, one for each thread
  • 1 MB L2 cache (lockable by the GPU) running at half-speed (1.6 GHz) with a 256-bit bus
  • 51.2 GB/s of L2 memory bandwidth (256 bit × 1600 MHz)
  • 21.6 GB/s front-side bus (On the CPU side, this interfaces to a 1.35 GHz, 8B wide, FSB dataflow; on the GPU side, it connects to a 16B wide FSB dataflow running at 675Mhz.)
  • Dot product performance: 9.6 billion per second
  • Restricted to in-order code execution
  • eFuse 768 bits
  • ROM (and 64 KB SRAM) storing Microsoft's Secure Bootloader, and encryption hypervisor
  • Big endian architecture

    • XCGPU

    The Xbox 360 S introduced the XCGPU, which integrated the Xenon CPU and the Xenos GPU onto the same die, and the eDRAM into the same package. The XCGPU follows the trend started with the integrated EE+GS in PlayStation 2 Slimline, combining CPU, GPU, memory controllers and IO in a single cost-reduced chip. It also contains a "front side bus replacement block" that connects the CPU and GPU internally in exactly the same manner as the front side bus would have done when the CPU and GPU were separate chips, so that the XCGPU doesn't change the hardware characteristics of the Xbox 360.

    XCGPU contains 372 million transistors and is manufactured by GlobalFoundries on a 45 nm process. Compared to the original chipset in the Xbox 360 the combined power requirements are reduced by 60% and the physical chip area by 50%.

    Illustrations of the different generations of processors in Xbox 360 and Xbox 360 S.

    References

    Xenon (processor) Wikipedia
    (Text) CC BY-SA