Hands-On Testing: 26 Modems: Faster Than 14.4 Kbps

Is faster better even when standards are in flux? We stress-test 26 high-speed modems to identify the best for today's business applications

Helen E. Holzbaur

The more characters per second your modem can transmit, the smaller your telephone bill will be. This month, we tested 26 modems that can shave communications costs by operating at speeds faster than the current CCITT V.32bis standard of 14.4 Kbps.

Fourteen of the modems anticipate the V.34 standard for 28.8-Kbps communication. The formal standard is expected to be announced around the time this issue reaches you. (For convenience, this report refers to the 28.8-Kbps modems as V.34, even though the standard isn't finalized and they canno t be considered "official" V.34 products.) The remaining 12 modems employ 19.2-Kbps communication, known as V.32terbo, which is a de facto high-speed communications standard that has been promoted by AT&T as an upgrade to V.32bis.

Why should you consider nonstandard modems? These high-speed modems excel when you can match like products at both ends of your communications link. When connected in this way, modem interoperability is not an issue, so the higher speeds of either 19.2 or 28.8 Kbps translate directly into cost savings.

What's more, in both modem classes, many vendors promise free or inexpensive upgrades to the new standard when it's officially announced (see the "Roll Call" on page 178). Falling prices are an added incentive for buying a high-speed modem. In our last Lab Report on modems ("V.32 or Better: 69 Modems," July 1993 BYTE), the average price for a 14.4-Kbps modem was $532. The V.32terbo average in this report is $452. An even bigger difference can be seen on the high end. Las t year, 28.8-Kbps modems averaged $955; this year, you can buy one for an average of $580.

If you need to communicate with customers or electronic services that use 9600-bps or 14.4-Kbps modems, all the modems that we tested in this report are designed to drop back to the slower speeds. Also, all but four modems in our sample offer 9600-bps or 14.4-Kbps fax capability. To help decide whether you should choose a V.34 or V.32terbo modem, look at the text box "V.34 Versus V.32terbo" on page 170.

To judge the best modems in each class, we measured their performance when sending files in one direction over a "normal" telephone line, as well as their ability to simultaneously transmit and receive over the same line. We also measured throughput over six different types of unstable lines (e.g., those that use satellite links) to see which modems could operate at high speeds in harsh, real-world conditions.

The ability to connect with other modems and fax machines rounded out our performance testi ng. Overall, each modem withstood about 10 hours of testing.

How to use this guide

For both V.34 and V.32terbo modems, we have selected the best overall (which considers both data and fax performance), the best low-cost model, and the best modem for data-only applications.

Measured in bytes per second. Higher numbers indicate faster performance.

Measured in bytes per second. This is the average throughput over six simulated telephone lines with varying degrees of impairments.

A rating based on the completeness of each modem's set of features.

A rating of how easy the modem is to install and operate.

The DTE (data terminal equipment) rate is the maximum speed at which the modem can receive data.

The percentage of modems the test modem successfully communicated with at speeds faster than 14.4 Kbps.

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Illustration: Modems, Inside and Out INTERFACE The key to how easy a modem is to use. Be sure status lights are clearly illuminated and that their la bels are easily understood. CPU The chip responsible for processing commands and compressing data. PROM This holds modem software and, depending on the chip set used in a particular modem, can be used for upgrading performance. See the "Roll Call" for a listing of which modems can be altered via PROM replacement to support the V.34 standard when it is finalized. RAM Modems typically use 4 KB or less, but modems with larger amounts (e.g., the Hayes Optima 28800 V.FC + Fax with 16 KB) speed data compression for faster overall performance. SERIAL PORT A 16C550 high-speed buffered UART (universal asynchronous receiver/transmitter) is required for maximum throughput with V.34 modems. Some, including Boca's V.Fast Class External Bocamodem, come bundled with a 16C550 serial card.