Beware HSP Modems. When you buy your next modem, you could innocently
buy an HSP modem, not realizing the limitations of what you're buying. Short for
host signal processor, HSP modems use fewer and cheaper chips compared to
traditional modems. The work normally done by the missing chips is transferred to
software running on the host computer's main processor (the Pentium, PowerPC).
How do you know if it's an HSP modem?
U.S. Robotics Winmodems are the most popular HSP modems. USR sells
their Winmodems as OEM products to other vendors. The IBM 56K Internet Kit is
an OEM Winmodem. If a modem is advertised as Windows-only, it is probably an
HSP model. Rockwell's 14.4 RPI modems also use HSP. So do Apple's GeoPort Telecom Adapters for Power Macintoshes. The GeoPorts for Quadra AVs are slightly different, in that they use the host computer's digital signal processor (DSP), rather than the host computer's CPU. A popular synonym for HSP modems is "controllerless modems."
There are a number of flaws in the HSP concept. In all cases, your host
computer has to do more work to make up for the modem's lack of hardware.
Users of Winmodems often notice a slowdown on their main computer with all but
the fastest CPUs. One RPI modem user reported slow transfer rates and dropped
connections until he upgraded his PC from eight to sixteen megabytes of RAM
(which improves performance in Windows). IBM's minimum requirements for
the 56K Internet Kit modem is a 486, but some features require a 90 MHz
Pentium, and DSVD features require a 133 MHz Pentium.
Note that U.S. Robotics Winmodems have an on-board DSP that takes care of
basic modulation and de-modulation tasks, so the load on the host computer is minimal. A number of USR Winmodem users have written in to say that they have been very pleased with the performance of their modem, and hadn't noticed any slowdown on their computer.
The other big disadvantage of HSP modems is that the software needed to
make them work is operating-system dependent. Apple's GeoPort Telecom
Adapters require the Mac operating system, so they won't work with MKlinux or
Be OS. Winmodems are Windows-only, so they can't be used with Linux, Solaris, OpenStep, or OS/2 unless someone writes special drivers. In contrast, any external Hayes-compatible modem with a full chip set can be used with any operating
system on any computer with a serial port.
Even if you don't plan to run Linux on your PC, you may want to play modem-to-modem games like Doom that run in DOS. DOS games generally won't work with Winmodems, unless DOS drivers are provided. Major exception: Quake will still work, because Quake runs in a DOS shell under Window, and uses the Windows network drivers.
Winmodem configuration can be messy, because Winmodems use a range of memory addresses instead of a fixed memory address. Winmodems require a DLL file that loads into memory at startup, using some of Windows' resources.
The upgradeability of HSP modems is mixed. RPI modems aren't upgradeable
to anything beyond a 14.4. After years of delays, Macintosh finally released a free
33.6 software upgrade for the 14.4 Power Mac GeoPorts, but not the Quadra AV Geo Ports. No plans for a 56K upgrade have been announced. U.S. Robotics has a free 56K upgrade for the Sportster Winmodem model #1125, but the Winmodem Vi models aren't upgradeable.
If Winmodems have these problems, why do they continue to sell? In part, the
answer is cost. By omitting a few chips, manufacturers can sell Winmodems for twenty to fifty dollars less than traditional modems. But Winmodems are also popular for features like DSVD (digital simultaneous voice and data) and answering machine features, which are easier to implement with an HSP modem.
In general, I recommend avoiding HSP modems. Get a good old-fashioned
modem with all of its chips intact. Nothing else offers the same level of reliability, compatibility, and performance. The small savings of buying a Winmodem doesn't compensate for the load it shifts to your expensive new Pentium. And if you're an online gamer, you definitely want to avoid Winmodems. Winmodems have their advantages. If you plan to only use Windows, and if gaming isn't your thing, a Winmodem can save you money, and it may offer more telephony features
than a similarly-priced modem.
- Les Jones