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    SubjectRe: [RFC] New timeofday proposal (v.A1)
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    On Thu, 2004-12-09 at 08:57 +0100, Ulrich Windl wrote:
    > On 8 Dec 2004 at 15:36, john stultz wrote:
    >
    > [...]
    > > Take a look at the adjtimex man page as well as the ntp.c file from the
    > > timeofday core patch. There are number of different types of adjustments
    > > that are made, possibly at the same time. Briefly, they are (to my
    > > understanding - I'm going off my notes from awhile ago):
    > > o tick adjustments
    > > how much time should pass in a _user_ tick
    >
    > tick adjustments are considered obsolete, because if a lcok implementation (or
    > hardware) is severly broken, users should reject using that stuff. Meaning: tick
    > adjustments are ment to be set once in the life of a computer system. No
    > continuous tuning.
    >
    > > o frequency adjustments
    > > long term adjustment to correct for constant drift),
    >
    > Actually, you are compensating for a "tick problem" on a smaller scale (constant
    > part), and variations caused by temperature, voltage, and others (variable part).
    >
    > > o offset adjustments
    > > additional ppm adjustment to correct for current offset from the ntp
    > > server
    > > o single shot offset adjustments
    > > old style adjtime functionality
    > >
    > > Tick, frequency and offset adjustments can be precalculated and summed
    > > to a single ppm adjustment. This is similar to the style of adjustment
    > > you propose directly onto the time source frequency values.
    > >
    > > However, there is also this short term single shot adjustments. These
    > > adjustments are made by applying the MAX_SINGLESHOT_ADJ (500ppm) scaling
    > > for an amount of time (offset_len) which would compensate for the
    > > offset. This style is difficult because we cannot precompute it and
    > > apply it to an entire tick. Instead it needs to be applied for just a
    > > specific amount of time which may be only a fraction of a tick. When we
    >
    > Yes, that's the "precise" variant of implementing it. Poor implementations are
    > just accurate to one tick.

    Thanks for your knowledgeable clarifications. Its good to know someone
    out there deeply understands this stuff more then at a "this is what the
    code is doing, and I have my own interpretation as to why" level. :)

    thanks again,
    -john


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