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| Source: Andrews, J., & Bakers, N. (2006). XBOX 360 System Architecture. IEEE Micro , 25-37. |
The Power PC was designed to provide a single architecture that could be used for a broad assortment of processor environments. This means that the PowerPC architecture must be both flexible and scalable. Flexibility allows the design to be either hardware or software based. Scalability allows the performance of the system to increase as hardware and capacity is added. The Xbox 360 is one example of a system that uses this computer architecture.
The PowerPC architecture has a few of the following features:
- Based off of a RISC instruction set
- Uniform-length instructions to allow simplified instruction pipelining and parallel processing instruction dispatch mechanisms
- The ability to perform both single and double-precision floating-point operations
- Physically separate storage and signal pathways for instructions and data
- Support for big and little-endian modes
- A complete 64-bit specification that is backward compatible with the 32-bit mode
- Supports multiple CPU cores
Why would Xbox use this architecture?
A game console needs to provide value for an extended period of time. In order for this to happen, a system will need to be able to run at peak performance for a variety of different work loads, gaming engines, and other game requirements as they change over a number of years.
The Xbox 360 uses the PowerPC RISC Architecture to provide flexibility and performance. The RISC instruction set limits the amount of stored memory being used, and instead increases performance for a given operating frequency by relying on internal registers and an L2 cache to optimize simple instructions. This architecture also takes advantage of symmetric multiprocessing. In this case, 3 identical CPU processors are connected to the same 512 MB DRAM memory. This improves gaming performance further, as programs can be written to optimize each CPU for a given purpose. Furthermore, the I/O chip offers a wide variety of options for external communication.
In depth information can be found at IBM developer Works. Check out the PowerPC Architecture Books I-III
Understanding the PowerPC Architecture is also a very informative (yet heavy) read
