12-28-2015, 05:18 AM
(12-28-2015, 04:59 AM)Kommander Wrote: LPAE on ARM processors
...has been introduced long ago (Cortex-A15/A7) to solve the hard 4 GB limitation that would otherwise exist due to ARMv7 being a 32 bit architecture. Does that mean that any A15/A7 SoC is able to address more than 4 GB physical memory? Of course not. This depends on the SoC in question. Most if not all Allwinner SoCs are able to address 2 GB physical memory (16Gb) and the A64 is now able to use 3 GB (24Gb) when modules become available.
Since the A64 is a tablet SoC this memory limitation is acceptable. Other ARMv8 SoCs target other uses and therefore they're able to address much much more physical memory (AMD's A1100 for example is able to use up to 128 GB).
BTW: LPAE limits you to a 40 bit address space (ARMv7) while ARMv8 is able to use an 48 bit address space. LPAE is still there since "for compatibility reasons, we still support the entire ARMv7 machine in the new ARMv8 architecture" (quoting ARM).
HTH