Cable modems require extremely clear signals, and quite often any existing cable wiring in your house just won't do. So they have to drill new holes and string higher-quality cable into both the regular cable TV boxes and to the cable modem. Once premium-grade coaxial cable has been strung in your home, the cable modem is connected to the same wire that goes into your TV, and it sends and receives data over a single channel of the 125 available under most setups. Like a DSL setup, the cable modem must connect to an Ethernet card installed in your PC or the built-in Apple Talk connection in a Mac. The biggest advantage that DSL enjoys over cable is that DSL connections tend to give you the same speed uploading stuff to others on the Internet as the 1.5 mbps download speeds.
Cable modems allow much slower uploads than downloads.
RCN, for example, only lets me upload stuff at about 30 percent of the download speed. This is OK by me. N. Michigan Ave., Chicago, IL 60611.