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Windows 98 > Communication Tips

Increase Modem Speed in Windows 98


In Windows 98, your modem may seem to work fine, but the true fact is, the baud rate for you COM Port doesn't allow you to reach top-speed. To improve your port's speed:

  1. Click Start, Select Settings > Control Panel, open System
  2. Click the Device Manager tab, and click on the "+" sign next to Ports (COM & LPT)
  3. Select the port your modem uses, click Properties, then click the Port Settings tab, and set the Bits per second to 115200 bps, that way you won't have a sort of filter on the Port.

    115200 bps is the maximum setting for a "Standard" COM port. If you encounter problems, try setting this value lower. With System Monitor you can check if there are any problems. System Monitor (sysmon.exe) can be Installed by starting the Add/Remove Programs Properties in Control Panel, select the Windows Setup tab, double click on the System Tools entry and select System Monitor

    (If you are not sure which COM port your modem uses, click on the "+" sign next to the Modem Icon in Control Panel and select your Modem. Click on Properties and choose the Modem Tab. Here you will see the COM port used by your modem)

  4. For most Modems you can use Hardware in the Flow control drop-down box

The Maximum speed at which Windows 98 communicates with the modem is set in Control Panel > Modems, click the Properties button on the General tab. Windows 98 selects a conservative default speed, to prevent data loss on slower computers. So if you are using a fast computer (defined by MS as a 80486 or Pentium), set a faster speed here. If applications report data errors, lower your speed.

In Windows 98 Microsoft opted for some limited support of the setting known as MaxMTU in Windows 95.

  1. Select your Dial-Up Adapter from Network in Control Panel
  2. Click Properties and select the Advanced tab
  3. In the selection box on the left, select IP Packet Size
  4. Now you can select a setting in the Value drop-down box, choices are: Automatic, Large, Medium and Small
  5. The settings Large, Medium and Small will put a IPMTU value in the registry entry for your Dial-Up Adapter of respectively 1500, 1000 or 576

For for more information, visit the HelpWithWindows Web Site. Here you'll find info on the MaxMTU fix, and other settings to increase your comm's speed.

It is not widely known, but the serial ports on motherboards and add-in cards that use some specific I/O controllers will support operation at speeds greater than 115200 bps:

  • ALI:
    M1543(Aladdin V south bridge)

    Serial ports provided by these chips will run at 230400 and 460800 bps.

  • NS:
    PC87307 / 87317
    PC97307 / 97317

    Serial ports provided by these chips will run at 230400 / 460800 / 921600 bps.

  • SMC:
    37C665IR / 666IR
    37C669 / 669FR,37N769
    37B72x / 77x / 78x / 80x,37C67x / 68x / 93x / 93xAPM / 93xFR,37M60x / 61x,37N958FR

    Serial ports provided by these chips will run at 230400 and 460800 bps.

  • WinBond:
    W83877TF (TF only, A/F/AF not supported)
    W83977F /AF /TF / ATF

    Serial ports provided by these chips will run at 230400 / 460800 / 921600 bps.

All they need is the proper software to enable and program these high speed modes.

For Win95/98, getting greater than 115Kbps requires two parts:

  1. Executing a small program at boot time to enable the high speed mode
  2. An updated serial.vxd that knows how to program the high speed rate

The file SHS17.ZIP from provides all you need to determine if your serial ports are compatible and, if so, to take advantage of the high speed operation that these chips support.

Increase Modem Speed in Windows 98