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Annotation of embedaddon/ntp/html/hints/solaris.xtra.4023118, revision 1.1

1.1     ! misho       1:  Bug Id: 4023118
        !             2:  Category: kernel
        !             3:  Subcategory: other
        !             4:  State: integrated
        !             5:  Synopsis: sun4u doesn't keep accurate time
        !             6:  Description:
        !             7: 
        !             8: [ bmc, 12/20/96 ]
        !             9: 
        !            10: The clock on a sun4u drifts unacceptably.  On a typical 143 mHz Ultra,
        !            11: the clock took 1.0001350 seconds to count 1 second.  While this may seem
        !            12: trivial, it adds up quickly.  In this case, the TOD chip will have to
        !            13: pull the clock forward by 2 seconds every 4 hours and 7 minutes.
        !            14: This drift rate is so high, that the clock is close to being too broken
        !            15: for NTP to guarantee correctness (in order for NTP's mechanism to work,
        !            16: it must be assured that the local clock drifts no more than 20 ms in 64
        !            17: seconds;  this particular 143 mHz Ultra will drift by nearly 9 ms in that
        !            18: period).  This problem has been reproduced on virtually all sun4u
        !            19: classes.
        !            20: 
        !            21: The fundamental problem lies in the kernel's perception of ticks per
        !            22: second.  The PROM is responsible for determining this figure exactly,
        !            23: and the kernel extracts it into the variable cpu_tick_freq.  On sun4u's,
        !            24: this number is disconcertingly round:  143000000, 167000000, 248000000,
        !            25: etc.  Indeed, a simple experiment revealed that these numbers were
        !            26: quite far from the actual ticks per second.  Typical was the 143 mHz
        !            27: Ultra which was discovered to tick around 142,980,806 (+/- 10) times
        !            28: per second.
        !            29: 
        !            30:  Work around:
        !            31: 
        !            32:         Integrated in releases: s297_27
        !            33:  Duplicate of:
        !            34:  Patch id:
        !            35:  See also:
        !            36:  Summary: