The 32-bit ARM Cortex-A cores, except for the Cortex-A32, implement the ARMv7-A profile of the ARMv7 architecture. The main distinguishing feature of the ARMv7-A profile, compared to the other two profiles, the ARMv7-R profile implemented by the ARM Cortex-R cores and the ARMv7-M profile implemented by most of the ARM Cortex-M cores, is that only the ARMv7-A profile includes a memory management unit (MMU).[1] Many modern operating systems require a MMU to run.
The 64-bit ARM Cortex-A cores as well as the 32-bit ARM Cortex-A32 implement the ARMv8-A profile of the ARMv8 architecture.
Arm Holdings neither manufactures nor sells CPU devices based on its own designs, but rather licenses the processor architecture to interested parties. ARM offers a variety of licensing terms, varying in cost and deliverables. To all licensees, ARM provides an integratable hardware description of the ARM core, as well as complete software development toolset, and the right to sell manufactured silicon containing the ARM CPU.
Silicon customization
Integrated device manufacturers (IDM) receive the ARM Processor IP as synthesizableRTL (written in Verilog). In this form, they have the ability to perform architectural level optimizations and extensions. This allows the manufacturer to achieve custom design goals, such as higher clock speed, very low power consumption, instruction set extensions, optimizations for size, debug support, etc. To determine which components have been included in an ARM IC chip, consult the manufacturer datasheet and related documentation.
Instruction sets
The Cortex-A5 / A7 / A8 / A9 / A12 / A15 / A17 cores implement the ARMv7-A architecture.[2] The Cortex-A32 / A34 / A35 / A53 / A57 / A72 / A73 cores implement the ARMv8-A architecture. ARMv8-A architecture provides exclusive loads and stores instructions as synchronization primitives.[3] The Cortex-A55 / A65 / A75 / A76 / A77 / A78 cores implement the ARMv8.2-A architecture. The Cortex-A510, A710 and A715 cores implement the ARMv9-A architecture. The Cortex-A520 and A720 cores implement the ARMv9.2-A architecture
Documentation
A typical top-down documentation tree is:
IC Manufacturer's high-level marketing slides
IC Manufacturer datasheet for the exact physical chip
IC Manufacturer Reference Manuals — describes common peripherals and other aspects of physical chips within the same series
ARM Core Reference Manuals — for the exact ARM core processor within the chip
ARM Architecture Reference Manuals — includes detailed description of all instruction sets of the core[2]
IC Manufacturers usually have additional documents, including: evaluation board user manuals, application notes, getting started with development software, software library documents, errata, and more.
