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posted by martyb on Monday November 20, @11:02PM   Printer-friendly
from the good-question dept.

https://www.10stripe.com/articles/why-is-56k-the-fastest-dialup-modem-speed.php

If you've ever had dialup internet service, or still do, or just know someone that does, you have probably heard terms like "56k modem". "56k" has become almost synonymous with dialup Internet access. But it's such an arbitrary number. It's not divisible by ten, it's not a power of two... so why was it chosen as the fastest dialup speed? For the answer, we will have to travel back in time quite a while.

Our visitors from Google should be warned that this is not a "stripped down" explanation; it is intended for relatively technical readers. But if you really want to know where this magic number comes from, you need to understand some of the technical background. As we shall see, "56k" was not just pulled out of a hat.

[...] Anyone that has ever used a dialup modem knows full well that they don't actually get to connect at that speed, though. And that their connection speed varies each time they dial in. There are two factors at work here.

The first is the FCC. If you are in the United States, the FCC places a restriction on the power output of devices connected to the phone network. The result is that you will never be able to connect at a speed faster than 53.3 kbit/s.

The second is the overall complexity of the phone network. 56 kbit/s (or 53.3 kbit/s) requires very good operating conditions, as it is really operating beyond the paramaters of what the phone network is required to be capable of. Operating at these speeds requires that there only be one ADC between the user and their ISP (which is not guaranteed to be true, but typically is), and that the copper wiring in the user's "local loop" have very good electrical properties. Part of the dialup process that is used to initiate a connection is an evaluation of the overall quality of the connection; if it is determined to be lacking, the modem will automatically drop down to a lower data rate.


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  • (Score: 1) by khallow on Tuesday November 21, @04:24AM (2 children)

    by khallow (3766) Subscriber Badge on Tuesday November 21, @04:24AM (#1333691) Journal
    I shall go lick my wounds. But it is possible that vux984 had found a way to achieve said speeds. Or that your modems were nerfed somehow. I read this interesting bit in the Wikipedia article [wikipedia.org] on US Robotics modems in Wikipedia.

    There was a licensing key needed for some Courier V.Everything V.90 flash upgrades. The firmware could be loaded onto the modem, but it would work in "degraded" V.34 mode. After paying a fee, and having the modem dial USR, a license key was installed that enabled the V.90 functions.

    The V.34 mode [wikipedia.org] would have the speeds you stated you achieved, if I read that article right:

    V.34 (10/96) is an updated ITU-T recommendation for a modem, building on the V.34 standard but allowing up to 33.6 kbit/s bidirectional data transfer. Other additional defined data transfer rates are 31.2 kbit/s, as well as all the permitted V.34 rates. Modems implementing this standard were often marketed under the moniker V.34+.

  • (Score: 2, Informative) by drussell on Tuesday November 21, @04:42AM (1 child)

    by drussell (2678) on Tuesday November 21, @04:42AM (#1333693) Journal

    But it is possible that vux984 had found a way to achieve said speeds.

    No, it is not. That is not a thing.

    How do you propose said speeds could be achieved on two USR Courier V.Everything modems on analog POTS lines?! 🙄

    There was a licensing key needed for some Courier V.Everything V.90 flash upgrades. The firmware could be loaded onto the modem, but it would work in "degraded" V.34 mode. After paying a fee, and having the modem dial USR, a license key was installed that enabled the V.90 functions.

    The Wikipedia article is wrong. SPORTSTER modems could be purchased with the necessary hardware to do 56k, but not capable of 56k out of the box. Many of them weren't intentionally hobbled, the early ones were pre-V.90 spec and were FREE to upgrade, then later any ones intentionally purchased as 33.6k-only models could still always be field upgraded to 56k, the TI DSP hardware was cheap and they always had the physical capability, just the firmware had to be updated. The physical hardware was the same between models except the ones that were voice / no voice (had the audio jacks on them or not.)

    ALL Courier models are fully upgradeable within the limitations of the physical hardware model capabilities. There was never any 33.6k-only Courier that wasn't just a free download away from being 56k. (or 14.4 -> 16.8 or whatever)

    • (Score: 2) by drussell on Tuesday November 21, @05:26AM

      by drussell (2678) on Tuesday November 21, @05:26AM (#1333696) Journal

      Actually, that might not be totally wrong on the Courier upgrades, if someone had an early 28.8 or 33.6k Courier and DIDN'T take advantage of the free upgrade to X2 offer, I think USR probably did the charged upgrade thing to go to a 56K standard (X2 or later V.90) but I think once you had one at X2 it was free to add V.90 and later, at least back in the day. Who knows, USR has been sold multiple times now, no idea what they would try to charge for an upgrade file on an ancient model today HAHA

      I know I never had to actually pay anything to upgrade any of my Couriers but that WAS like 20 years ago now. They still sold them until fairly recently, now I think there's just one generic Sportster V.92 model still produced for the traditional serial interface, basically just as replacements in legacy systems I would suppose...