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    SubjectRe: atomic RAM ?
    On 04/08/2010 11:28 AM, David Newall wrote:
    > Will the system use multiple cores? If it's only single core, perhaps
    > atomic operations are really necessary?
    At the moment I am just planning a single core NIOS project. But SMP is
    a decent option for NIOS, as it is no hardware problem - and often has
    been requested - to design multiple CPUs in a single in such an FPGA and
    run SMP Linux on it.

    OTOH, to do FUTEX in full (MMU) - Linux, atomic operations are
    definitively necessary, as in Userland you can't disable the interrupt
    without a Kernel call (which to avoid FUTEX is all about.) Currently the
    plan with the NIOS (MMU, non-SMP) arch is to simulate atomic operations
    with the said "atomic region" (as is done with e.g. the BlackFin arch).

    (BTW.: when enumerating the ways how atomic macros are done I forgot to
    mention the "new ARM" method: dedicated "load locked, store conditional"
    operations that help simulating atomic behavior in user space without
    the Kernel's help.)


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