XBOX 360 Architecture

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XBOX 360 Architecture

• Jake Seigel
• Darren Peters

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Stuff well talk about
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Odds and ends about the Xbox 360

• Released in a variety of versions with varying
  hardware.
• Hard Drives 20GB, 60GB, 120GB
• Xbox Live Arcade
• Compatibility with Original Xbox
• Halo is wicked

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The System
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The CPU

• Xenon, based on IBMs PowerPC Instruction set
  architecture
• 165 million transistors
• 3 cores, each core clocked at 3.2GHz
• Each core contains 2 symmetric multithreading
  hardware threads
• Also implements the VMX128 SIMD vector
  instruction set

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The CPU Cores

• Each core has 32KB L1 instruction cache, and 32KB
  L1 data cache
• All cores share 1MB L2 cache
• Each core implements in-order issuance
• Each core also implements the VMX128 SIMD
  instruction set. This has been customized for
  graphics workloads.

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Why In-Order Issuance?

• Out of order issuance allows instructions to
  execute faster, as instructions waiting for data
  do not hold up instructions waiting in the queue
• In-order cores take up less space on the chip
• In-order cores use much less power (lol)
• Two simultaneous threads make in-order processing
  much more efficient than traditionally thought
• In-order issuance is simpler, aiding design and
  implementation

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The VMX128 SIMD Instruction Set

• Single-Instruction Multiple-Data
• Contains 128 128-bit registers per hardware
  thread
• Contains instruction sets for floating point,
  permutation, and simple computations
• Includes an instruction specifically for
  computing dot-products, common to graphics
  applications
• The CPU can compute 9.6 billion
  dot-products/second

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The CPU
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The GPU

• ATI Xenos R500 (runs at 500Mhz)
• eDRAM framebuffer on a separate chip
• 32GB/s connection between parent and daughter
  chips

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Features

• Unified Shader Architecture
• No distinct vertex or pixel shader engines
• Adjusts automatically to the load
• DirectX 9.0 and HLSL 3.0
• Capable of vector and scalar operations with
  single-cycle throughput

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More Features

• 16 texture fetch engines feeding the shaders
• 16 programmable vertex fetch engines with
  built-in tessellation
• 16 interpolators in dedicated hardware
• Allows a form of data streaming called Xbox
  Procedural Synthesis. (One way data transmission
  from the CPU to the GPU)

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Even more features

• The GPU supports shader data to be exported
  directly to a buffer in memory.
• This allows the 360 to natively support GPGPU
  processing.

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Performance

• 500 million triangles per second
• 16 gigasamples per second using 4X FSAA
• 48 billion shader operations per second
• 96 shader calculations per cycle (at peak)

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The others

• The Xboxs heatsinks are actively cooled by a
  pair of 60 mm exhaust fans.
• Microsoft added an aluminum heat sink to cool the
  GPU in Xboxs made in late 2007
• The 360 eats 116.48 kWh which will cost you
  20.10 a year to play it about 2 hours a day

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References

• http//hardware.teamxbox.com/articles/xbox/1144/Th
  e-Xbox-360-System-Specifications/p1
• http//www2.computer.org/portal/web/csdl/doi/10.11
  09/MM.2006.45
• http//en.wikipedia.org/wiki/Xbox_360_hardware
• http//www.xbox.com/en-AU/support/xbox360/manuals/
  xbox360specs.htm
• http//www.eetimes.com/news/latest/showArticle.jht
  ml?articleID197006869
• http//www.beyond3d.com/content/articles/4/
• Jeff Andrews, Nick Baker, "Xbox 360 System
  Architecture," IEEE Micro, vol. 26, no. 2, pp.
  25-37, Mar./Apr. 2006, doi10.1109/MM.2006.45

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And now, one last look at our faces