The Power Processing Element (PPE) comprises a Power Processing Unit (PPU) and a 512 KB L2 cache. In most instances the PPU is used in a PPE. The PPU is a 64-bit dual-threaded in-order PowerPC 2.02 microprocessor core designed by IBM for use primarily in the game consoles PlayStation 3 and Xbox 360, but has also found applications in high performance computing in supercomputers such as the record setting IBM Roadrunner. The PPU is used as a main CPU core in three different processor designs: The Cell Broadband Engine (Cell BE) which is used primarily in Sony's PlayStation 3 gaming console. It uses the PPE and comes in three versions, a 90 nm, a 65 nm and a 45 nm part. The PowerXCell 8i which is a version of the Cell BE with enhanced FPU and memory subsystem. It was only manufactured as a single 65 nm version. The XCPU which is used in a three core configuration and a unified 1 MB L2 cache inside Microsoft's Xbox 360. It comes in three versions, the 90 nm and 65 nm versions, and the 45 nm XCGPU with an integrated graphics processor from ATI. Main features 64-bit, dual-threaded core 3.2 GHz typical clockrate 32 KB L1 instruction cache 32 KB L1 data cache 512 KB unified L2 cache, 8-way set associative in the PPE variant. Compatible with 64-bit PowerPC ISA v.2.02 (POWER4 and PowerPC 970) AltiVec SIMD functionality Execution units Branch Unit (BRU) Fixed Point Integer Unit (FXU) Load and Store Unit (LSU) Floating-Point Unit (FPU) Vector Media Extension Unit (VMX) In-order The PPU is an in-order processor, but it has some unique traits which allow it to achieve some benefits of out-of-order execution without expensive re-ordering hardware. Upon reaching an L1 cache miss - it can execute past the cache miss, stopping only when an instruction is actually dependent on a load. It can send up to 8 load instructions to the L2 cache out-of-order. It has an instruction delay pipe - a side path that allows it to execute instructions that would normally cause pipeline stalls without holding up the rest of the pipeline. The instruction delay pipeline is used for the Out-Of-Order Load/Stores: cache misses are put there while it moves on. The PPE's pipeline The PPE has a 23 stage general pipeline with an additional 11 stages possible for microcode and an additional 4 stages possible for