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Opening Arguments

Snooze it or lose it

You probably haven't been losing any sleep wondering about this, but in the digital age, a snooze alarm could be any length of time. It's nine minutes because of the limitations of tehcnology when the alarm was invented:

Alarm clocks in 1956 had standardized gears. The snooze gear needed to mesh with the teeth of the other gears. Due to the configuration of the gears, a 10-minute snooze cycle was out of the question, so the engineers had to choose between nine minutes or 10-plus minutes.

And we live in America, chock-full of that whole Protestant work ethic, so the engineers went with nine minutes. Don't dare be late for work or you'll end up a miserable failure.

The nine-minute interval carried into the digital age. Some early digital clock designer probably took a look at an old mechanical clock and decided nine minutes was the standard.

Love my snooze alarm. On work days, I set the alarm for just over an hour before I have to get up -- that's seven snooze alarms. But that means you have to wake up eight times in one morning, say the morning-loving ntwits who like to bound out of bend and tackle the day with zest. But I get to go to sleep seven times in the same morning -- that's the point.

Posted in: All about me, Science


Harl Delos
Mon, 07/14/2008 - 11:13am

Actually, I think you'll find that it's not exactly 9 minutes. It's 9 minutes, 9.25 seconds - and it has nothing to do with mechanical clocks.

It has to do with the standard 4.77MHz clock rate of the most ultra-cheap computer timer chips.

The folks at IBM weren't sure how well the original IBM PC-1 was going to sell, so they went to outside suppliers for operating systems (PC-DOS, CP/M-86, UCSD p-system) and they cobbled together the hardware from existing off-the-shelf hardware. It was quick to market, at limited investment.

To regulate the speed of the bus, they used an off-the-shelf oscillator intended for TVs. It produces 14.318 MHz, which is 4 times the 3.579 MHz frequency of the color subcarrier of baseband video. Since the cheapest 8088 chip from Intel was certified for 5 MHz, they divided that 14.328 by 3 to get 4.77 MHz. Well, 4.77266667 to be precise, but we call it 4.77 MHz.

Voila, you end up with a 4.77 MHz computer, and every electronic engineer designs chips to work at that speed, so it will be compatible.

Now, start counting the cycles on a digital chip. The number 262144 is 1,000,000,000 000,000,000 in binary. That number takes about 9.15 minutes. (9 minutes, 9.26 seconds).

If you had a full-fledged computer there, it would be no problem to make it closer to 9 minutes or to 10 minutes, but it's a lot cheaper to wait for the number to roll over.

There's an automatic air freshener on the market that shoots perfume into the air every 9, 18 or 36 minutes, for the same reason that digital clocks have a 9-minute snooze - because it's just as good to do it that way, and it's cheaper.

Some early digital clock designer probably took a look at an old mechanical clock and decided nine minutes was the standard.

The folks at the Journal-Times probably didn't take a look at digital timer circuitry, and decided that clock designers are fools. They might, in fact, be fools, of course, but not as foolish as the J-T columnist who could have learned the real answer for the price of a phone call. Most electronic engineers have dealt with timer circuits and cost constraints.

Mon, 07/14/2008 - 12:31pm

Now that's the kind of geeky surplus of information for which I come to the Internet!

For a long time, I took the snooze button as concrete proof that there was no Devil. If there was, he wouldn't go through all sorts of contortions to get a person's soul. Instead, he'd just pop up when the snooze button was going off for what would otherwise be the last time, and offer another 9 minutes in exchange.

I stopped using them when my kids started getting me up well before I had to start getting ready for work.