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    SubjectRe: IRQF_SAMPLE_RANDOM question...
    On Wed 8 Apr 2009 19:16, Chris Friesen pondered:
    > Gilles Espinasse wrote:
    > > Readme say :
    > > "This daemon attempts to collect real randomness from fluctuations of
    > > high-frequency clocks on a PC's mainboard. The basic assumption is that
    > > mainboard and CPU are clocked by two separate physical clocks."
    > > How large is this basic assumption true, on x86, on other arch?
    > Isn't the cpu frequency normally a phase-locked multiple of the
    > mainboard bus frequency?

    Yes - typically they are the same.

    However - I have tested clrngd out on a Blackfin, and found it gave an
    excessively high load - but it did give ok results. 77% of the time (659/848
    times) it provided results that passed it's built in FIPS test. It did die a
    few times (if the FIPS tests fails 5 times in a row clrngd aborts).

    I was going to write my own (based on a similar architecture) - but use the
    RTC clock and the main clock - since those actually would be different
    physical crystals - and the accuracy of low cost 32kHz crystals is crappy
    (typically measureable with a high enough core clock).

    But I think delays of cache misses/flushes will dominate things anyway - which
    is why clrngd works today on systems which are using the same clock source.
    (but since it will be RTC interrupt driven, vs while(1){} like clrngd - the
    load will be much lower).


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