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* 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 designs, and the Cortex-A53 and A57 are ARMv8A designs.
== Confusing Numbering Schemes ==
The ARM space is littered with really awful and conflicting numbering schemes.
* Early ARM chips had numbers that were different from the corresponding architecture levels. For example, the ARM11 processor is an ARMv6 chip, which is much lower-performing than other parts with lower numbers, including the ARMv7-level Cortex-A5, -A7, -A8, and -A9 devices.
* Cortex designations are not in order of release date, performance, features, or power consumption. Cortex-A8 and Cortex-A9 are some of the older designs in the series; Cortex-A15 chips add hardware virtualization support. Cortex-A12, Cortex-A7, and Cortex-A5 designs followed, with varying power/performance profiles. Cortex-A53 and -A57 chips are ARMv8.
* Other companies have introduced chips with confusingly similar designations. The Apple A7 chip is not an ARM design and has nothing to do with the Cortex-A7 (or any other Cortex core); it is roughly in the same performance category as a dual-core Cortex-A53.
