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AnchorDesk

David Coursey
Why your PC is no better than a $15 wristwatch

David Coursey
Executive Editor, AnchorDesk
Wednesday, July 3, 2002
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Working behind the scenes, a small government agency headquartered outside of Denver operates a network of 14 servers capable of changing the operating systems on your PC--and millions of others--in less than a second.

These servers interact with susceptible computers some 550 million times a day. Yet most people don't know they exist, the special protocols that control them, or even the nature of their mission.

Major computer manufacturers and operating system developers are also part of the conspiracy: Both Microsoft and Apple have included special code in their latest OSes that lets this shadowy network carry out its mission.

And what, exactly, is that mission? Making sure your PC knows what time it is.

SORRY TO GO ALL Art Bell on you there. But I'm interested in time--especially computer time--the way some people are obsessed with the government's role in hiding space aliens.

Which is why last week I found myself talking to a physicist who has made time the focus of his professional life. He told me something interesting: "Real clock people," he said, "don't use Windows."

Or any graphical user interface, for that matter. In fact, real clock people don't trust their computer's clock for much of anything. Why? Because as soon as you've set the clocks--yes, that's plural--inside your PC, they start to wander. And if you don't reset them often, those little errors can add up to seconds per day and minutes per week.

For example, the computer I'm using right now can gain or lose as much as 1.3 seconds in a hour. That may not seem like much to you, but it means I can't count on it alone to run my radio program--where seconds of dead air can seem like hours--each day.

THAT'S WHERE that shadowy government agency--better known as the National Institute of Standards and Technology, a part of the U.S. Commerce Department--comes in. It operates those 14 time servers to synchronize clocks connected to the Internet.

The people who use NIST's Internet Time Service range from Windows XP and Mac System X users, whose systems automatically consult time servers to set their clocks, to stock brokerages that use those servers to keep their systems accurate to within 3 seconds, as mandated by the SEC.

Public safety agencies use these servers to determine what happened when for legal purposes. Some computer systems base their security regimes on time synchronization--again using the NIST's servers as reference points. The only time stamps that federal courts will accept are those with an audit trail that links directly back to an NIST time server.

I KNOW ALL THIS because I spent the better part of an afternoon reading everything I could find out about time on the NIST Web site and then speaking with NIST physicist Judah Levine.

Among other things, Levine is the author of the free NISTime client software. Both Windows XP and Mac OS X have their own built-in time clients. There are also many shareware time clients available for downloading.

All these applets connect to time servers, operated by the NIST or someone else, using a protocol called NTP (for Network Time Protocol) or a variant called SNTP, with the "S" standing for simple.

According to Dr. Levine, people who want accurate time should choose a client that will synchronize the PC clock several times a day. It should also compensate for Internet latency. Every packet takes time to traverse the Net, but the amount of time is different for virtually every packet sent. While some time clients attempt to take this lag into account, their success at doing so varies.

Assuming your client corrects for both the Internet delay and your clock's normal drift, it should keep your system accurate to within a few milliseconds at all times. The best Dr. Levine has ever achieved, using a best-case Internet connection, is accuracy to within 10 millionths of a second when compared to the atomic clocks at NIST in Boulder, Colo.

UNFORTUNATELY, the clients in Windows and Mac OS aren't ideal. They share two problems: First, they may not synchronize often enough. The default--and unchangeable--synchronization interval for Windows XP is one week. That's better than nothing, but not good enough to let me use my PC's clock during my radio program.

Mac OS X doesn't say how often it synchronizes the time, though a quick check found the clock on my iMac tightly synchronized with the radio clocks in my office (about those, see below). I suspect the interval may be adjustable someplace in the Unix system that underpins OS X, but I haven't found where that someplace is yet.

Another potential problem for computer clocks is the servers they sync with. Both Microsoft and Apple operating systems default to time servers operated by the respective companies. How sure are we that those servers are correct?

One final problem with PC clocks: You remember how my physicist friend told me that real clock people don't use graphical interfaces? It's because the UI takes up so many processor cycles that it causes a "jitter" in the PC's software clock. That overhead, plus the inherent inaccuracy of software clocks (not to mention the battery-operated hardware clock that keeps time when your computer is powered down) means a PC will never be closer than some number of milliseconds to the actual time. And that's if you reset the PC clock hourly, the way some of my computers do.

THE SUM RESULT of all these problems: Your PC is probably no better than a $15 wristwatch at keeping accurate time. If I had to rely on my PC's clock, I'd probably install either NISTime (for Windows) or one of the better shareware or freeware products. But being a time wonk, I don't use computer time very much. Instead, I rely on some other alternatives.

I recently started buying radio-controlled clocks that automatically synchronize themselves every evening and are designed to stay accurate even when they don't sync for a few days.

These clocks used to cost $1,000 or more (some still do). But a power increase at the NIST's WWVB radio station (it operates on 60KHz long-wave) allowed for the development of less expensive models. I've paid as little as $19.95 for the small Oregon Scientific clocks I use during the radio program and take with me as a source of accurate time when I'm broadcasting outside the studio.

Radio clocks come in a wide variety of sizes and shapes--from wall clocks to wristwatches--as well as prices. You can find a list of vendors at the NIST Web site.

IF YOU'RE REALLY, really serious about time, the most accurate option is provided by the constellation of Global Positioning System (GPS) satellites. Each of these birds carries its own atomic clock. In addition to helping people on the ground get their navigational fixes, these satellites transmit time pulses.

Using a special receiver costing in the neighborhood of $10,000, GPS can provide time down to a few nanoseconds. (Nano being 10 to the -9th power; milliseconds are 1/1000th of a second.) You can link your computer to some consumer GPS receivers; while the time won't be to the nanosecond, it will be plenty close enough for most purposes.

Believe it or not, I've really just scratched the surface of this topic. The NIST Time and Frequency site has more detailed explanations, lots of links, vendor lists, and a 7-page paper detailing the failings of PC clocks.

But search as I might, NIST and even the patient Dr. Levine were unable to answer my most important and perplexing question: If I always know exactly--OK, to a few milliseconds--what time it is, why am I always so late?

For that, I'm told, I should skip the physicists and head for a psychiatrist.

Do you know what time it is? Have I gone completely off the deep end? Any other time wonks out there? TalkBack to me!

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