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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: 2) by jman on Tuesday November 21, @05:13PM (4 children)

    by jman (6085) Subscriber Badge on Tuesday November 21, @05:13PM (#1333750) Homepage
    My VIC-20 held about 100K per side (assuming a 30-minute tape), but given how tiny those BASIC programs were, never needed more than a handful of tapes.

    After upgrading to the C64 and splurging on the floppy drive (actual 5-1/4", not those pretend not-really-floppy 3-1/2" things), total storage per media actually went down a little as it was only 170K (single sided, double-density), but oh so much faster than loading from tape!

    Many in the Enterprise world still use tape for archival.
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  • (Score: 2) by drussell on Tuesday November 21, @07:29PM (3 children)

    by drussell (2678) on Tuesday November 21, @07:29PM (#1333775) Journal

    It's pretty bad when C64 floppy seemed fast for you at the time. :)

    It's the slowest floppy interface ever.

    SO painfully slow!!

    • (Score: 2) by jman on Wednesday November 22, @12:02PM (2 children)

      by jman (6085) Subscriber Badge on Wednesday November 22, @12:02PM (#1333853) Homepage
      Well, it *was* forty years ago; most computers were slower. The V20 chip (an NEC clone of Intel's 8088) I used to build a DAS machine in the latter 80's ran at a whopping 5Mhz, which just blew away the C64's 1.something from a six or so years earlier.

      Now I have an "aging" i9 clocking billions of cycles per second, and even interprative languages run pretty quickly on it, given enough memory.

      The floppy comment was that it way faster than loading from tape.
      • (Score: 2) by drussell on Thursday November 23, @04:37PM (1 child)

        by drussell (2678) on Thursday November 23, @04:37PM (#1333980) Journal

        Well, it *was* forty years ago; most computers were slower.

        No, they weren't. Not the floppy data transfer rate.
        The C64-style floppy interface was by FAR the slowest, it's not even close!

        Commodore 1541: 400 bytes/sec
        Commodore parallel IEEE (PET): 1,800 bytes/sec
        Atari 810: 2,400 bytes/sec
        Apple Disk ][: 15,000 bytes/sec
        IBM PC 360kB: 32,000 bytes/sec
        IBM AT 1.2MB: 64,000 bytes/sec

        The floppy comment was that it way faster than loading from tape.

        It wasn't really, though. If the tape you were loading used a tape fastloader like Turbo 250 instead of the slow (even for tape) stock 300 baud C64 protocol, you could get 540 bytes/sec from tape. This is significantly faster than the stock 1541 drive's transfer rate.

        Sure, you can do various types of fastloaders or custom firmware on the 1541 and some methods even managed to get as high as 10,000 bytes/sec (still only ⅔ the speed of a stock Apple Disk ][ !!), but Commodore's "home" line was the only crap where fastloaders ever really needed to be a thing, because their stock performance was so utterly abysmal.

        • (Score: 2) by jman on Friday November 24, @01:17PM

          by jman (6085) Subscriber Badge on Friday November 24, @01:17PM (#1334030) Homepage

          That was not my experience. Using the tape drive I had from the Vic-20, it would take, say, two and a half minutes to load a game. From the floppy, it was under a minute.

          Not going to argue about theoretical specs, just what I actually saw.