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Application processors

So far we've talked about microcontrollers, such as the Arm Cortex-M series. These are typically small systems with very limited resources.

Larger systems with more resources are typically called application processors, built around processors such as the ARM Cortex-A or Intel Atom.

For simplicity we'll just work with QEMU's aarch64 'virt' board.

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• Broadly speaking, microcontrollers don't have an MMU or multiple levels of privilege (exception levels on Arm CPUs, rings on x86).
• Application processors have more resources, and often run an operating system, instead of directly executing the target application on startup.
• QEMU supports emulating various different machines or board models for each architecture. The 'virt' board doesn't correspond to any particular real hardware, but is designed purely for virtual machines.
• We will still address this board as bare-metal, as if we were writing an operating system.

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