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    SubjectRe: [PATCH] (comments requested) adding finer-grained timing to PPC add_timer_randomness()
    >> In the 2.4 tree we have code that works out a cpu features word from
    >> the PVR value. The cpu features word has bits for things like does
    >> the cpu have the TB register, does the MMU use a hash table, does the
    >> cpu have separate I and D caches, etc.
    >
    >Reading the PVR is probably faster in this case, since you avoid a
    >potential cache miss. As I said in an earlier message the __USE_RTC macro
    >should be made dependent on whether the kernel supports 601 or not.

    The CPU features will nop-out sections of code that don't apply for
    a given CPU if you use the assembly macros. If you nop'out a couple
    of instructions, you win over reading the PVR, masking out bits,
    comparing, and doing a conditional branch.

    Ben.



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