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→Implementations of ARMv8
ARM licenses their technology at several different levels:
* An ''architectural'' licensee has the right to develop their own implementation of a particular ARM architecture. Apple (A7+ CPU) and Applied Micro (X-Gene) fall into this category. These chips execute standard ARMv8A software, but because the designs are prepared by the licensees, the performance profiles may be different from those of other manufacturers and those designed by ARM - for example, branch prediction and pipelining may be different, and some instructions will be slower while other instructions are faster than the corresponding ARM-designed devices. Therefore, optimizations may have different effects. To perform appropriate optimizations for a particular implementation, a compiler can use a "cost table" which contains information about the performance of specific instructions, enabling the compiler to pick the optimal combination of instructions for a particular operation.
* A ''design'' licensee has the right to produce devices using one or more of ARM's chip designs. This requires far less expertise on the part of the licensee, and allows what is basically a cut-and-paste of the standard ARM core(s) into the chip design that the licensee is working on. This enables the licensee to focus on the other IP (intellectual property) blocks on the chip, such as GPUs, memory controllers, radios (cellular, wifi, bluetooth, GPS, zigbee, and so forth), accelerators, and various peripherals. Most ARM licensees fall into this category. Current standard ARM chip designs are designated "Cortex" - the Cortex-A5, A7, A9, A12, A15, and A17 are ARMv7A ARMv7-A designs, and the Cortex-A53 , A57, and A57 A72 are ARMv8A ARMv8-A designs.
== Confusing Numbering Schemes ==