3.2.2. Effect of Device ID multiplexing

GIC-500 supports transporting the Device ID over awaddr_s for GITS_TRANSLATER writes, which reduces the size of awuser_s in the system. See AXI4 Slave Interface. This is invisible to software and is a system integration decision.

To support this, the address space required in the system might be larger than the normal address map, with the normal address map occupying the lower part of the address space. Given the maximum 20 bits of Device ID, this can only be the case for some systems with fewer than nine cores.

If transporting the Device ID over the address bus, the total address space required is (in bits):

max(18 + max(1, ceil(log2(total_number_of_cpus))), device_id_width + 2)

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