Sportster x2 modem craves the fast lane but often gets stuck in traffic

The Sportster x2 does transmit significantly faster than conventional V.34bis modems.
What neither x2 or K56Flex can give you yet is full, bidirectional 56-kilobit/sec
throughput [GCN, March 17, Page 65].


There are several barriers within this speed trap. For starters, the x2 delivers full
speed only when pushing information downstream from a provider's server to you. When you
upload, you're stuck back at the 33.6-kilobit/sec V.34bis rate. That's fine for browsing
the World Wide Web or getting e-mail, but it's no better than other modems for dialing in
remotely or posting Web.


The next barrier is that the x2 modem can't attain a full-bore 56 kilobits/sec anyway,
because Federal Communications Commission regulations prohibit downstream speeds greater
than 53 kilobits/sec over ordinary telephone lines.


Even if the FCC took this rule off the books, x2 couldn't reach full potential. Its
efficiency depends on the distance between your PC and your dial-in service and on local
line quality. In the real world, you're more likely to see rates on the order of 44
kilobits/sec.


There are other performance barriers. For example, an x2 modem can only connect at its
top speed with an x2-compliant server modem. You couldn't refit, say, your agency's
bulletin board system with standard x2 modems and expect any speed gain for most users. To
get a boost, you'd have to install x2 server modems or terminal servers, and the callers
would need x2 modems themselves.


Furthermore, an x2 works only when connected directly to a digital telephone switch. If
your calls happen to be routed though an analog private branch exchange, you won't get the
x2 performance advantage. Even with newer digital PBXes, the x2 may not work. If calls
will go over any PBX, be sure the x2 modem can talk to it before you buy.


That said, an x2 in the right situation is faster than an ordinary modem and much, much
cheaper than a 56/64-kilobit/sec Integrated Digital Services Network line because there
are no ISDN installation fees or tariffs.


Out of the box, the x2 looks just like the rest of the Sportster family. When you begin
set up, though, you'll notice some differences. Instead of a floppy disk, you get a CD-ROM
with drivers for Microsoft Windows 3.x, Windows 95 and NT only.


For the moment, Apple Macintosh users are out in the cold. But they do have a
short-term option. Because the x2 functions are loaded into firmware, many U.S. Robotics
modems-all 33.6-kilobit/sec Sportsters and many Couriers-can upgrade to x2 with a $60
piece of software.


Aging MS-DOS communications applications will have fits with x2. You can make them work
only by spending a lot of time exploring the mysteries of the venerable Hayes AT modem
command set, as amended by U.S. Robotics.


Installing the driver software on a PC running Microsoft Windows 95 takes no more than
two minutes.


You're all ready to go-if you have an x2 server system to dial into. For now, that
means you'll be limited to a few Internet providers and a handful of special numbers for
large online information services.


U.S. Robotics is trying to persuade other modem makers to adopt x2. Rivals Lucent
Technologies Inc. of Murray Hill, N.J., and Rockwell International Corp. are doing the
same with their K56Flex variation. As usual


in such battles, the two 56-kilobit/sec standards currently are incompatible.


The head start belongs to x2, but in the war over standards and sales, we won't know
who won until the numbers are in. Fortunately, because both standards are
software-upgradeable, the x2 modem that you buy today is far less likely to become
obsolete if K56Flex wins than were the losers in the V.32 vs. PEP modem wars of years gone
by.


Do you really need a x2 modem? For many situations, no. But if your service provider
has jumped aboard the x2 bandwagon and the users in your office mostly download data
rather than send it, x2 makes a lot of sense.


Steven J. Vaughan-Nichols is a computer journalist in Lanham, Md.


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