). The results were decidedly mixed.
Up and Running
Even with plug-and-play hardware, installation continues to be the weakest link for many products. Physically, connecting the external Sportster to a COM port or plugging in the internal Connecta was easy. However, in both cases, trying to follow the explicit step-by-step software-installation guide left me puzzled.
Right off the bat, Windows 95's auto-detect feature failed to notice either modem. An explicit hardware search missed the Sportster and thought the Cardinal was a COM port. I finally tossed the instructions, installed the modems "manually," and began dialing.
With both modems, I saw connection speeds as high as 4
9 Kbps. But the stability and usability of those x2 connections were marginal. The x2 modem's downlink speed often dropped back from its initial connection speed. In some cases, I wound up with a slower connection than I obtained with a standard 33.6-Kbps modem. And on highly compressible data, download speeds were slower than when using a 28.8-Kbps modem.
I consulted extensively with USR's technical support regarding these results, even to the point of loading the modem's ROM with updated software. There was no noticeable improvement, however. USR speculated that the problem was located in the phone line I used for the test. That line did, however, pass the USR LineTest diagnostic connection program, which pronounced it x2-capable (see the sidebar "USR's LineTest: Check It Yourself and See").
Despite the spotty results of this informal testing, there are still several good reasons to make the switch to an x2 modem. If your current modem is slower than 28.8 Kbps, you're overdue for an upgrade anyw
ay. An x2 device will give you all the speed of a 33.6-Kbps V.34 modem -- along with the potential for higher speeds -- for about the same cost.
If your phone-line conditions are favorable and your local Internet service provider (ISP) offers x2 service, you can see download speeds approaching 53 Kbps, although uploads remain limited to a maximum of 33.6 Kbps. Combine this potential speed increase with the low cost and flash-ROM upgradability of these units, and they represent true bargains.
Counting Bits
There's a big difference between testing a technology and testing the application of that technology. The theoretical basis for x2 is sound. And in a lab full of test equipment, there's little dispute that you could easily demonstrate an asymmetrical transfer rate of 33.6 Kbps up to, and 56 Kbps down from, an x2 provider's digital modem. But, as my testing showed, the theory has little bearing on what you see in the real world.
A casual test of the x2 technology is far mo
re difficult. It's not enough to simply time how long it takes to download a file or load a Web page. You have to consider the factors that control the perceived speed across an Internet connection. For example, variables that change from connection to connection include local and long-distance phone conditions, the load at the local phone office, the response of the local ISP, and so on.
Over the course of four days, I initiated over 100 x2 dial-up sessions at various times of the day and night, connecting via long-distance lines to USR's x2 point of presence (POP) and x2 BBS in Illinois. I also tried my local provider's x2 POP over local lines. Given my high expectations, the experience was disappointing.
My initial sign-ons indicated connection speeds ranging from a paltry 33.3 Kbps to an exciting 49.3 Kbps. But these initial speeds don't tell the whole story. After connecting, an x2 modem automatically drops down to 33.3 Kbps and then renegotiates back up to the highest reliable speed it can m
aintain.
I interrupted these sessions periodically to query the modem as to its actual connection rate and found that, despite the initial connection speed, the downlink rate never exceeded 40 Kbps. Uplinks topped out at about 24 Kbps. When I connected to the same provider using a 28.8-Kbps modem, I achieved a 26.4-Kbps rate for both the uplink and the downlink.
Should You Buy?
Modems using K56flex, a competing 56-Kbps standard that's promoted by modem-chip maker Rockwell and backed by the likes of Lucent and Motorola, were just coming out after I completed my tests. Despite this jockeying within the industry, it's easy to forget that neither x2 nor K56flex are actual standards. Instead, they're similar to the early independent attempts at establishing Class 2 commands for fax modems and V.FC modulation. U.S. and international committees are working on standards, but they aren't likely to appear until next year.
Does buying an x2 modem make sense? If you're running on a st
andard analog phone line, want incrementally improved download speed without the hassle and cost of ISDN, and have a local ISP that's x2 compatible, then it certainly does. In areas that have better local lines than mine, it's reasonable to expect better results than I observed. Even in the worst case, an x2 modem makes an economical and easily upgradable V.34 device.
Product Information
Sportster 56K Faxmodem..................................$219 external
........................................................$199 internal
U.S. Robotics
Skokie, IL
Phone: 800-342-5877
Phone: 847-982-5010
Internet:
http://www.usr.com
Circle 1117 on Inquiry Card.
How Fast Is a 56-Kbps Mo
dem?
