US Robotics Winmodems 
and Rockwell HCF modems

What are software-based modems?

Bee.Net technical support handles hundreds of support requests every day. Of those centering on modem issues (severe connection, disconnection, or throughput problems), virtually every customer is using a software-based modem, and very often either a US Robotics Winmodem or a modem containing a Rockwell HCF chip. These are also the two most common modems shipped with new PC's.

All modems contain two main parts, a controller and a datapump. The controller includes the command set used to configure and then dial the modem, plus the routines for error checking and data compression. The datapump handles the actual sending and receiving of data.

As recently as two years ago, most controllers and datapumps were built with dedicated hardware chips, and we refer to modems with these designs as hardware-based modems. Since then, fast computer processors have become the norm and manufacturers have created modem chips that offload some or all of this work onto the processor. Both the USR Winmodem and modems with a Rockwell HCF chip are called winmodems or controllerless modems, because their hardware controller has been replaced with a Windows-based software driver. Other modems go a step further and replace both the controller and the datapump with Windows software. These are generally called host-based modems. (We suspect some "HCF" modems may also be host-based.) There are benefits and drawbacks to these designs:

Benefits:

• Since there are fewer chips and components, software-based modems reduce the retail cost by $50 or more, compared to the average hardware-based modem. By far, this is their biggest selling point.
  
  
• With fewer components, software-based modems draw less power, which can be beneficial for laptop computers and other battery-powered devices.
  
  
• Upgrading a software-based modem is a bit easier, since the modem's "brains" are just files on your hard drive. Theoretically, it's possible to take a 14.4K host-based modem and upgrade it to 28.8K, 33.6K, 56K, and beyond, by changing only the software driver. (In reality, this has never actually happened.) Upgrading the modem is just like installing a new program.
  
  
• Most hardware-based modems are upgradeable, but traditionally you needed to replace a ROM chip on the modem board, which required returning the modem to the factory, or at least partly-dismantling the modem. Nowadays, most 56K hardware-based modems are upgradeable via software and a flash ROM, but there are still limitations. The upgrade consists of writing the new code to a ROM chip on the modem board, but any disturbance (like a power outage) might render the modem inoperable. The size of the ROM chip is fixed, unlike the free megabytes or gigabytes available on the average hard drive. Also, even though the controller and datapump code can be updated, there are still real limitations in the hardware, which generally keep hardware-based modem from spanning technology generations, like upgrading a 33.6K modem to 56K.
  
  
• Certain features like voice support are easier to implement.

• By nature of their design, software-based modems steal processor time, and can be dependent on factors like the computer's bus speed, memory, and processor cache. Winmodems require a Pentium-style processor or a solid '486. Requirements for host-based modems are higher, usually starting with a Pentium 133 or 150 MHz processor. Other processors, like those from AMD and Cyrix, or budget processors like the Winchip and the original Celeron, may have more stringent requirements or may not be supported at all. Heavy processor use by a software-based modem could cause sluggishness in other programs or modem disconnections. If you play Internet games, any software-based modem can be a liability, since most games expect full access to the processor.
  
  
• In their November 12, 1998 issue, PC Magazine found the US Robotics Winmodem used 25% of the processor time on a Pentium 133 computer. About the same time, CNet reported a Motorola host-based modem taking 39% and a PC-TEL host-based modem taking 36% of the processor time on a 200 MHz Pentium MMX computer. Another report claims a poorly-written Rockwell HCF driver grabbed a whopping 80% of the processor time (admittingly on an unspecified processor).
  
  
• Software-based modems (especially host-based modems) appear to be more sensitive to line noise.
  
  
• Software can crash, be deleted, become corrupt, or conflict with other software. Many people have experienced programs or Windows functions that suddenly stop working for no reason, and software-based modems have the same liability.
  
  
• Upgrades to Windows NT 5/Windows 2000 or beyond, could create incompatibilities with existing software-based modem drivers.
  
  
• Most software-based modems are based on newer chip and software designs, which may not have had time to mature.
  
  
• Since these modems' "brains" are Windows-only executable programs, they are not usable under other operating systems like Linux, OS/2, or BeOS...and sometimes even Windows NT. Often, this list also includes MS-DOS, which can cause problems for DOS-based modem programs and DOS-based modem-to-modem games.

Although we stand behind our statements, based on first-hand experience with customers, this doesn't mean thousands of customers aren't currently using software-based modems without problems. With a fast enough computer, you may have no trouble and not notice any difference.

How do I identify software-based modems?

How do you know a modem is software-based? Read the fine print:

• A modem is software-based if it absolutely requires Windows 95, 98, NT, or a Pentium processor. Put another way, software-based modems will not run under DOS, Linux, OS/2, etc. Many will not run on a 486 processor, and none will run on a 386 processor. If the documentation says the modem "harnesses the power of Windows", it means it!

 
• Virtually all PCI card modems are software-based. (One exception is the MultiTech MultiModem ZPX.) Since the companies making these modems want a low-cost product, they usually avoid the extra circuitry needed for an ISA interface. Most software-based modems have the PCI logic located right on the main chip.

 
• Look for obvious buzzwords like HCF, HSP, PC-TEL, AMR, MDC, RPI, winmodem, controllerless modem, soft modem, soft56k, and host-based modem. Another giveaway is modems whose name contains the word "Win", i.e. "Windows-based", "Wincom", or "Winstorm".

 
• Most software-based modems are designed for PC's running Windows 95 or higher, but several Macintosh software modems also exist, although they are no longer sold. These include Apple's line of GeoPort modems, and several 14.4 modems from Global Village like the Teleport Gold II.

Problems with Rockwell HCF modems usually fall into one of two categories: 1) the modem is unable to connect at all, or 2) the modem disconnects frequently and unexpectedly. We know of three possible fixes:

• Make sure you are using the latest driver. Rockwell HCF modems became prominent in the fall of 1998 when shipped with certain new PC's. Back then we discovered the installed driver was virtually unusable, and often required an immediate upgrade. Since then there have been several upgrades to the HCF driver, and several upgrades to Bee.Net's TotalControl code, but we continue to hear complaints. It is essential to check your modem or computer manufacturer's web page regularly and install any new driver they make available. Visit the V.Unreliable site for a list of the drivers various manufacturers are shipping.

 
• Because the Rockwell HCF modem is partly software-controlled, it emulates certain chips that are found on hardware-based modems. One such chip is the UART. Windows sometimes misinterprets the UART the HCF is emulating, causing side effects like disconnections. Follow these instructions to check the UART and fix the problem if necessary.

 
• The HCF modem has different characteristic than Rockwell's hardware-based (ACF) modems. For reasons we don't understand, it retrains much more aggressively, sometimes causing it to become unstable and disconnect. New drivers may fix the problem, or you may try limiting it's upper speed or disabling 56K entirely. See our 56K and V.34 modem strings page for specific modem strings.

The main problem we've seen with US Robotics Winmodems is slow throughput. Although the modem may connect at a high speed, its actual throughput may be only ¼ of this. The only fix we've found is to disable 56K entirely, which forces the modem to connect at a slower speed, but with a faster throughput. See our 56K and V.34 modem strings page for more information. As with Rockwell HCF modems, also make sure you are using the latest driver.

Upgrading the driver and limiting the modem's upper speed are also the main ways of fixing problems with other software-based modems.