COM port overrun errors in Microsoft Windows 95 and Windows NT - Netfinity 3000

Resolving The Problem

Symptom

Communication applications return or display COM port errors (CRC errors, packet errors, overrun data, terminal window character errors) when connecting at data rates of 57kbs and higher via external modems.

Affected configurations

This tip applies to the following IBM machine types pre-installed with Microsoft Windows 95, Windows 98 or Windows NT 4.0, and using the integrated S3 Trio 3D AGP video adapter.

• IBM PC300PL Series 6862/6892 systems
• IBM PC300GL Series 6275/6285 systems

This tip may also apply to IBM Netfinity 3000 systems pre-installed with Windows NT 4.0 and using the integrated S3 Trio 3D AGP video adapter.

The COM port error condition is only seen when using an external modem on either serial (COM) ports A or B. Internal modems are not affected.

Solution

To minimize the likelihood of COM port errors, the following steps are suggested for Windows 95, Windows 98, and Windows NT 4.0.

Disable "Show window contents while dragging" under "Plus!" settings under Windows 95 or Windows 98

1. Right click on the Windows 95 or Windows 98 desktop, then click Properties.
2. Click on the Plus! tab. If present, remove the check mark from "Show window contents while dragging" and click OK.

Reduce video hardware acceleration rate under the Video Performance tab under Windows 95 or Windows 98

1. Right click on the Windows 95 or Windows 98 desktop, then click on Properties.
2. Click on the Settings tab.
3. Depending on the installed version of Windows 95 or Windows 98, click on the Advanced Properties button, or the Change Display Type button.
4. Click on the Performance tab. Under Hardware Acceleration, move the settings slider to the second position, "Basic Accelerator functions..." and click OK.

Disable"Show window contents while dragging." Under Windows NT 4.0

1. Using the steps outlined above, disable "Show window contents while dragging."

Verify"FIFO Enabled" is checked under COM port settings

1. Click on Start, Settings, and Control Panel.
2. Double click on the Ports icon and highlight the appropriate COM port. Click on Settings.
3. Click on Advanced and verify that "FIFO Enabled" is checked.

For customers using the HyperTerminal communications application included in Windows 95 Windows 98, and Windows NT it is recommended that they download the updated "HyperTerminal Private Edition" directly from the Hilgraeve Internet web site at the following URL: http://www.hilgraeve.com.