Modem Help

Modem Speed

Below is an explanation of the modem speed variety from modem manufactures and the area in which you dial from.

Modem manufactures have long exaggerated how fast their modems are. Honesty ended at around 2400bps. Manufactures started claming that with data compression, that same 2400bps modem was good for 9600. The reality was that at best it was good for 4800, and only on text and other compressible data. No improvement at all on .ZIP files, which were the main thing people spent time waiting for before the Web existed.

Next came modems that really could reach 9600bps on a consistent basis, but manufactures were claiming they could go as fast as 38400bps, citing the same data compression garbage they did before. When 14.4kbps (14,400bps) modems came out, manufacturers tried to become more honest, and most did sell them as 14.4 modems. A few manufacturers still could not resist, and claimed speeds of 57600, or even (Hayes) 115200(!).

When 28.8kbps modems came out, the picture changed again. Unlike all the modems before them, 28.8 modems could often not reach their full rated speed. Under typical conditions, they connected at 21.6-26.4kbps, depending on phone line quality. 28.8 connects were very rare.

ISPs such as ILCS brought fiber optic lines directly into their phone rooms. This meant that while our end of the connection still had an analog phase, the cable run was reduced from thousands of feet to just a few feet. This reduced line noise enough that 28.8 was reachable most of the time. Data compression is not very useful for Internet access use because most program files, images, and sounds are already compressed before transmission, it yields a real but quite small performance increase, perhaps 20%. The upshot of this is that you loose almost nothing running your port at 38400 with a 28.8 modem, which is a good idea to prevent COM port errors.

Seizing the opportunity for more modem upgrades, modem manufactures came out with 33.6 modems. These modems could sometimes reach speeds of as high as 31kbps when connected to an ISP such as ILCS who had fiber right in their phone closet, but almost never at 33.6. Some manufacturers (Hayes come to mind) claimed that these modems are good for 230kbps with data compression, which is truly ridiculous given the pre-compressed nature of almost everything big you will be transferring nowadays.

56k modems are common now, and how fast do you think they go? I assume you won't be surprised when I tell you 42-48kbps is typical. These modems rely on a fully digital link to the ISP, so the only analog loop is to your house. Unfortunately, not all users see these increased speeds. If you are unlucky enough to have certain types of PBX's, multi-plexors, or line conditioners on your phone line, your speed will not increase at all with 56k modems.