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What is a Power Processor Element / PPE
Written by Abhishek Ghosh
The PPE is the Power Architecture based, two-way multithreaded core acting as the controller for the eight SPEs, which handle most of the computational workload. The PPE will work with conventional operating systems due to its similarity to other 64-bit PowerPC processors, while the SPEs are designed for vectorized floating point code execution. The PPE contains a 32 KiB instruction and a 32 KiB data Level 1 cache and a 512 KiB Level 2 cache. The size of a cache line is 128 bytes. Additionally, IBM has included an AltiVec unit which is fully pipelined for single precision floating point. (Altivec does not support double precision floating-point vectors.) Each PPU can complete two double precision operations per clock cycle using a scalar-fused multiply-add instruction, which translates to 6.4 GFLOPS at 3.2 GHz; or eight single precision operations per clock cycle with a vector fused-multiply-add instruction, which translates to 25.6 GFLOPS at 3.2 GHz.
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