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Download What Is Linux?
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developer.com - Reference V.17 14,400bps, 12,000bps, 9,600bps, and 7,200bps V.29 9,600bps and 7,200bps V.27ter 4,800bps and 2,400bps V.21 Channel 2 300bps A current trend in DOS and Windows systems is to use enhanced serial port devices, which are necessary to sustain the high baud rates that the modern fast modems can reach. Most of these devices are addressed as standard serial ports by the operating system, so they will work with Linux. Any accelerator device that requires a special driver, though, will not work unless you port the driver to Linux (not an easy task). Your standard serial ports should be at least 16550 UARTs (instead of the older 16450 UARTs) if you intend to run your modem at speeds higher than 9,600 baud. If you have an older PC, check with your dealer about upgrading the serial ports. The upgrade is usually very inexpensive and makes a major difference in modem performance with fast speeds. The 16550 UART has a 16-byte buffer, but the 16450 has only a 1-byte buffer. In general, the 16450 UARTs can only be used to 9,600 baud. Any higher throughput speeds require 16550 UARTs. Linux doesn't care whether your modem is an internal or external model, as long as it has a serial port designation that it can be addressed through. The choice between internal and external modem has become one-sided lately. Five years ago, the internal modem was the modem of choice. Most name-brand modems now are external, probably because of easier upgradability. Most manufacturers offer both types of modems. Note that internal modems save you a serial port on the back of the machine and almost always use a 16550 or faster UART. One thing to consider with many new modem models is their software upgradability. Some modems allow you to load new versions of the controlling software through a DOS session. You obtain the new software through a bulletin board or on-line service. This capability reduces the obsolescence factor considerably. Most new modems adapt themselves automatically to any of the adopted modem standards (as well as fax standards, if you purchase a fax modem). Installing a Modem If the modem you purchase is an internal modem, you must open your machine and add it in an unused slot. Make sure you set the communication port parameters to an unused value. Most internal modems are set by default to use DOS COM3 or COM4. These values also work with Linux, as long as you can copy the serial port device driver to those values. http://24.19.55.56:8080/temp/lsg13.htm (3 of 7) [3/17/2001 7:46:29 PM]
