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Linux was called 'obsolete' in 1992, and now it powers servers around the world (www.xda-developers.com)
submitted 2 months ago by to c/linux@lemmy.world
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[–] 2 points 2 months ago (2 children)

RISC literally just means reduced instruction set architecture. Any CPU that has a small amount of instructions (defined somewhat arbitrarilly) is considered to be a RISC CPU as opposed to a CISC (complex instruction set architecture) CPU. The idea behind RISC is to improve performance by reducing bloat, but the tradeoff is that performing more complex tasks takes more instructions to do.

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  • [–] 0 points 2 months ago (1 child)

    Yes, but they could have compatibility like x86. The difference is that every CPU creator can have different sets, not just a superset. That's why ARM is not well defined, because its by nature cannot be. There is no definition of what an ARM or RISC CPU has to offer or be compatible to.

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  • [–] 2 points 2 months ago

    ARM is a series of ISAs, which are strict definitions which CPUs must conform to to be considered ARM compatible. RISC has no set or sets of ISAs, and is more of a philosophy.

    If one company, like Mediatek or Qualcomm makes an AARCH64 CPU, compiles a binary for a common operating system, like Linux, and wants to run it on the others' CPU, that is possible because the ISA for AARCH64 is strictly defined.

    On the other hand, take two incompatible RISC architectures, say one CPU that uses MIPS and another RISC-V, and try to run binaries compiled for the other architecture, then try to run it. It will not run because they are inherently incompatible, even though they are both a subset of the wider RISC umbrella.

    Also depending on which ARM assembly programmer you ask, modern ARM isn't even really RISC due to its complexity despite the name. That is a whole other unrelated conversation, though.

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