Stalking Those Wild New Modems |
 |
by Nancy L. Ward |
Today, speeds of 28,800 bps and 33,600 bps (28.8/33.6Kbps) are the norm, with a wide assortment of brands and models to choose from.
Most of these modems are chip and/or flash (soft ware) upgradeable to 33.6K. A number of different V.34 chipset (28.8/33.6Kbps), including Rockwell/Lucent, US Robotics/Texas Instruments, Motorola, and A T & T are available. The new 56K standard is waiting in the wings; both Rockwell and US Robotics have filed new standards applications.
Although these new 56K technology modems will download at 56K, they will upload at only V.34 rates. In addition, your BBS or Internet Service Provider will need digital connections and special modems for this technology to be viable. "So, how do I make a choice between all this high tech equipment available to me?" you ask. Read on; maybe I can help.
What is a modem? Just as Windows is an interface between you and your computer, a modem is an interface between your computer and the phone lines. Today's technology translates output from your computer to phone signals, then translates the phone input back to computer language at the other end. Because the new 56K technology bypasses the analog-to-digital conversion to your computer, it can use nearly all of the available 64K (ISDN) bandwidth available to your BBS or Internet Service Provider for downloading. In order for computer and phone line translation to work between the myriad modems on the market, the International Telecommunications Union (ITU-T) establishes and ratifies standards for telecommunications. By complying with these standards, modem manufacturers assure users of compatibility between the various brands available. Be aware that not all manufacturers will adhere to these standards.
Although the 28.8K V.FC chipset (based on an early version of V.34) was rushed to market in an attempt to make it the de facto standard, ITU-T ratified the more robust and sophisticated V.34. Most newer modems meet this standard and, if backward compatible with V.FC, are generally advertised as V.everything. No matter what the manufacturers are saying, you would do well to be guided by the fact that the 56K standard will be decided and ratified by ITU-T, just as V.34 was. The final decision is not expected until late 1997. Individual manufacturers will not make the final decision!
Split Speeds: Some modems support split speeds, i.e., differing transmission and receive speeds. Say you had a transmission speed of 28.8K and a receive speed of 56K. Without split speeds support, your modem would be limited to 28.8K in both directions. So, to be upgradeable to 56K, a modem must support split speeds. How can you tell if a modem is a "split speed"? Generally you cannot tell by the box; however, you can have two things written on your receipt: 1. You can return the modem if it does not work in your computer and 2. Have the seller state on the receipt it is a split speed modem.
The UART chip and internal vs. external: Inside your computer, the UART chip (Universal Asynchronous Receiver-Transmitter) is used by serial devices, such as a modem, to communicate with your PC. The UART converts parallel data from your computer into a serial data stream and vice versa. If you have an older computer, chances are you have either an 8250 or 16450 UART, both of which have a single character buffer. This is OK if you plan to buy an internal modem, which has a UART-based serial port (or emulator) on board. Make sure it is 16550A or better. Internal modems are easy to install, are on a card that plugs into your PC's bus, and use your PC's power supply. On the other hand, external modems are self contained, incorporate a panel of lights to display current session information and aid in problem diagnosis and resolution. They can be powered on and off to reset independently from your computer. The down side is that an external modem uses a serial cable hooked to one of the PC's UART-based serial ports and doesn't have a newer UART, so if your computer has an 8250 or 16450 UART, you must correct the situation to get optimum performance from your high speed modem. Luckily, there are serial cards available which contain the latest 16550 UART. If it isn't soldered in, you can replace the chip on your motherboard.
What to avoid: RPI modems - Most don't have hardware error correction and data compression, and require you to use communication software that supports the RPI protocol. You are generally out of luck with an RPI modem if you use OS/2 or UNIX. Get an agreement from your vendor (in writing) that the modem can be returned if it turns out to be RPI. Avoid V.FC modems (nonstandard technology), el cheapo modems you have never heard of and generic brands. Again, it is virtually impossible to read on the box and determine if it is an RPI modem. Have the seller write on your receipt that is not an RPI modem.
What to look for: With the advent of the 56K modem, you may be best served to wait until the 56K standard has been set by ITU-T. No matter which standard is ratified (Rockwell or US Robotics), if you have a 28.8K modem that is either firmware or flash upgradeable to 33.6K and your modem supports split speeds, chances are good that you can also upgrade to 56K. Living with your old 28.8K or 33.6K (or even 14.4K) modem until the technology has matured will be a lot easier than making the mistake of buying something rushed to market (as so many did with V.FC) without being ratified by ITU-T.
If you just can't wait, at the very least, look for flash and/or firmware upgradeable to V.34, with V.everything preferred and get a guarantee from the seller that your modem can be upgraded. Check for split speeds support and backward compatibility with prior ITU-T standards. You will have better support and a better chance at future upgrades to 56K with a popular name brand. While you're at it, check out some of the other neat features in today's high speed modems, such as voice, speakerphone and caller ID. Finally, buy from a vendor that will allow you to return the modem if it doesn't work with your system.
To learn more about modems, visit Curt's High Speed Modem Page at http://www.teleport.com/~curt/modems.html and Navas 28800 Modem FAQ_ at http://users.aimnet.com/~jnavas/modem/faq.html .
Nancy Ward, a HAL-PC member, and is the HALNet Registrar.
E-mail me at webmaster@hal-pc.org with any comments you have and tell me what you want to see here.
Back to the Magazine Home Page