Re: Windows timekeeping - NTP

This is a discussion on Re: Windows timekeeping - NTP ; >>> I don't follow this part. The user uses Windows to do this setting, >>> right? So Windows could choose any timezone for the hardware clock, >>> and UTC would be a natural choice. Windows obviously asks the new >>> ...

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Thread: Re: Windows timekeeping

  1. Re: Windows timekeeping

    >>> I don't follow this part. The user uses Windows to do this setting,
    >>> right? So Windows could choose any timezone for the hardware clock,
    >>> and UTC would be a natural choice. Windows obviously asks the new
    >>> user what time zone he's in, and therefore when the user says what
    >>> time his wristwatch says, Windows knows what UTC that corresponds to.

    >
    >No, the user sets the initial time when they first build the computer and
    >go into the BIOS to set the configuration. Way before any OS is even
    >installed. Perhaps these days I should have said "system builder" or
    >something like that.


    So you're talking about the person at the factory, not the person who
    gets the computer from the factory, right.

    It's been ages since I've seen a computer fresh from the factory, but
    I assume it comes with Windows already on it and the first thing the
    user sees when he turns it on is a "welcome to Windows, let's set up
    your computer" dialog. This dialog asks what time zone you're in and,
    because it knows that even if it was set at the factory, the hardware
    clock would have drifted a lot, it asks what time it is. The program
    then sets the hardware clock, making a choice as to what time zone
    offset to use with it. It chooses the user's local time zone.

    With this scenario, the reason for that choice obviously is not
    because the user is comfortable with local time -- the user never even
    sees those numbers. It is apparently a matter of backward
    compatibility.

    It's also my impression that the system builder at the factory doesn't
    go into a BIOS screen to set the hardware clock, but that guy probably
    isn't relevant if the scenario described above happens later.



    >I think the history is that MS-DOS was originally an OS for isolated,
    >non-portable, machines operated by unsophisticated users, so local time
    >was the easiest concept for the users to handle. Unix was developed
    >by academics, so they were prepared to deal with more abstract concepts
    >and consider the long term.


    I don't think there's any way to compare the two design choices because
    the hardware MS-DOS ran on was the only hardware that had a clock that
    communicated in HH:MM:SS form, so was the only hardware that made you
    make a choice as to which HH:MM:SS standard you wanted.

    If anyone knows of a computer architecture besides ISA and stuff
    designed to be compatible with it that has a HH:MM:SS hardware clock,
    speak up, but all the other clocks I can think of maintain a single
    counter, and it's up to the OS to derive from it UT HH:MM:SS or local
    HH:MM:SS for use by humans.

    The hardware used in ISA wasn't even designed for a general purpose
    computer. The MC146818A chip is for use in _really_ tiny special
    purpose machines that must offload all their time computation. It's
    somewhat of a mystery that ISA designers chose to use that chip, but
    the fact that MS-DOS was already keeping time in similar fashion
    internally made is less strange than it would be otherwise. Maybe it
    was just really inexpensive.

    As for the choice to use local HH:MM:SS instead of UT HH:MM:SS, it
    seems to me that even keeping track of a time zone and computing DST
    was beyond the sophistication of DOS of the day, so maybe using UT
    just seemed pointlessly complex. After all, even today a kitchen
    appliance with a clock in it does not track UTC inside.

    --
    Bryan Henderson Phone 408-621-2000
    San Jose, California
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  2. Re: Windows timekeeping

    Bryan Henderson wrote:
    []
    > So you're talking about the person at the factory, not the person who
    > gets the computer from the factory, right.
    >
    > It's been ages since I've seen a computer fresh from the factory, but
    > I assume it comes with Windows already on it and the first thing the
    > user sees when he turns it on is a "welcome to Windows, let's set up
    > your computer" dialog. This dialog asks what time zone you're in and,
    > because it knows that even if it was set at the factory, the hardware
    > clock would have drifted a lot, it asks what time it is. The program
    > then sets the hardware clock, making a choice as to what time zone
    > offset to use with it. It chooses the user's local time zone.
    >
    > With this scenario, the reason for that choice obviously is not
    > because the user is comfortable with local time -- the user never even
    > sees those numbers. It is apparently a matter of backward
    > compatibility.
    >
    > It's also my impression that the system builder at the factory doesn't
    > go into a BIOS screen to set the hardware clock, but that guy probably
    > isn't relevant if the scenario described above happens later.


    Well, the first thing I would do would be to go into the BIOS and ensure
    that things like time were correctly set, so I'm probably not your average
    user!

    From what I've seen, the hardware clock is often almost correct (time
    zones apart). Windows will ask the user what time zone they are in - it
    doesn't make assumptions (although Pacific may be the default).

    Cheers,
    David



  3. Re: Windows timekeeping


    Bryan Henderson schrieb:

    > If anyone knows of a computer architecture besides ISA and stuff
    > designed to be compatible with it that has a HH:MM:SS hardware clock,
    > speak up, but all the other clocks I can think of maintain a single
    > counter, and it's up to the OS to derive from it UT HH:MM:SS or local
    > HH:MM:SS for use by humans.
    >


    The Sun SPARCstation IPC used an STMicroelectronics M48T02 chip (or
    its equivalent predecessor) as its TOY clock. The data format is
    YY:MMD d hh:mm:ss ['d' is the day of the week in the range 1-7].
    I'd guess that other Sun models of that era used the same technology.

    Paul


  4. Re: Windows timekeeping

    Paul.Croome@softwareag.com wrote:

    > Bryan Henderson schrieb:
    >
    >
    >>If anyone knows of a computer architecture besides ISA and stuff
    >>designed to be compatible with it that has a HH:MM:SS hardware clock,
    >>speak up, but all the other clocks I can think of maintain a single
    >>counter, and it's up to the OS to derive from it UT HH:MM:SS or local
    >>HH:MM:SS for use by humans.
    >>

    >
    >
    > The Sun SPARCstation IPC used an STMicroelectronics M48T02 chip (or
    > its equivalent predecessor) as its TOY clock. The data format is
    > YY:MMD d hh:mm:ss ['d' is the day of the week in the range 1-7].
    > I'd guess that other Sun models of that era used the same technology.
    >
    > Paul
    >


    Digital Equipment VAX and Alpha computers used the chip from a wrist
    watch as a TOY clock. It kept seconds, minutes, hours, days and months
    but not years; the year was handled by storing the year on disk each
    time the clock was reset. (If you didn't do a SET TIME or reboot your
    system at least once a year, it would boot up with the wrong year!)

    It's an idea that makes sense; why "roll your own" when you can get one
    off the shelf for pennies.

  5. Re: Windows timekeeping

    Paul.Croome@softwareag.com wrote:

    > The Sun SPARCstation IPC used an STMicroelectronics M48T02 chip (or
    > its equivalent predecessor) as its TOY clock. The data format is
    > YY:MMD d hh:mm:ss ['d' is the day of the week in the range 1-7].
    > I'd guess that other Sun models of that era used the same technology.
    >
    > Paul


    I wonder why they needed the day of the week. In case they couldn't
    figure out what century they were in?

    Danny
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