Transfer Terminology

Bits vs. Bytes

We should tackle one last tangent before going into the different ways of connecting to the net - download and upload speeds. A lot of people write in to us and ask "why is it that my 56K modem doesn't give me a download speed of 56K/second?" The answer lies in a little trick that marketing people rely on. Modems are rated by kiloBITS per second, not kiloBYTES, which people are more familiar with.

When you talk about file sizes you always refer to them as kilobytes or megabytes, not kilobits or megabits. However, connection speeds and networking hardware are commonly measured in kilobits per second, or in the case of high speed connections, megabits per second. 8 bits = 1 byte, so doing the conversion you see that 56kilobits = 7 kilobytes.

Also, 56K modems are currently limited to a maximum transmission of 53 kilobits per second or so due to FCC regulations. Factor in the overhead of TCP/IP and your modem and the highest download speed you'll ever see on a 56K modem is probably 5 or 6Kilobytes per second.

You already knew that

The point of going through this is to bring your expectations down a couple of notches if you decide to make the jump to high speed cable modems or DSL. So when you sign up for that cable modem advertising "10 Megs per second download," keep in mind that you're not getting 10 Megabytes per second - you'll be getting 10 MegaBITS per second or 1.25 megaBYTES per second.

That's still quite an incredible transfer rate, so you should be more than pleased to get that kind of performance. After all, 1.25 megabytes per second means that you could have downloaded the 100MB Kingpin demo in 80 seconds. For the sake of consistency, the rest of this article will refer to connection speeds in kiloBITS and megaBITS, not BYTES.