Aaron Kulkis wrote: > Billie Walsh wrote: >> Somewhere in the past I read that computers are wonderful machines. >> Capable of great things. BUT, they are horrible clocks. >> >> The way it was explained was that when system use was high and resources >> were strained the clock was the last thing to get updated. Thus, it >> looses time. I'm sure it isn't near the problem it was many years ago >> but if your a power user it still could be a problem. > > This is precisely why NTP was invented -- it solves this > problem by obtaining time from calibrated time servers, > and also takes into account network latency. Level 0 > sources are atomic clocks (such as run by the US Naval > Observatory -- navies have VERY high interest in extremely > accurate timekeeping because accurate navigation depends > on it), Level 1 sources obtain their time from Level 0 > sources, Level 2 from Level 1, etc. Most Level 0 and > Level 1 sources are not for use by the general public.
Actually, there are several types of stratum (not level) 0 clocks. You can get receivers that will get time from GPS, CDMA cell phone network or a time & frequency standard broadcast such as WWV in the U.S. or CHU in Canada. Of course, all of those are traceable to some national atomic clock and all can be considered stratum 0. > > Level 1 sources prefer that only 1 or a very very small > percentage (like 1 in a 1000) of an organization's > machines get time from the Level 1, and then use > those hosts as Level 2 time hosts, which are then > to serve the rest of the organization. > > Do not under ANY circumstances get NTP time from > a Level 0 time server without explicit permission > from whoever owns or has the responsibility of > operating it. If you need a level 0 time server, > then you can get a device which recieves a radio > signal from a US Navy Observatory, and connects > to a communications port in your computer. These > tend to run in the US $100 - $200 range, and will > provide time accurate within 1 microsecond. Actually, the signal comes from WWV or WWVB in Colorado or similar station (WWVH) in Hawaii. Many other countries have their own time & frequency standard broadcasts, such as CHU in Canada. You can also get an accurate time source from the PBS television network in the U.S. This is often used to set clocks in TV's and VCR's. I have a clock here, that receives the signal from WWVB. I bought it from a consumer electronics store. > > > In most NTP configuration files, the CMOS clock on the > motherboard is rated as level 10 (kind of a "last resort"). > I have no idea why onboard CMOS clocks are less > accurate than a US $5 wristwatch which includes an > LCD display in that price. > > > That would depend entirely on the accuracy of the crystal used. Watches often have trimmers, which allow the oscillator to be adjusted to improve accuracy. I have never seen one on in a computer. -- Use OpenOffice.org <http://www.openoffice.org> -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
