IBM Support

ISDN external modems fail to connect at high speeds - IBM PC Server 310, 315, IntelliStation Z Pro (Type 6899)

Troubleshooting


Problem

Systems equipped with ISDN external modems connected via either serial port fail to connect at communication speeds of 128kbps or higher.

Resolving The Problem

Source

RETAIN tip: H16219

Symptom

Systems equipped with ISDN external modems connected via either serial port fail to connect at communication speeds of 128kbps or higher.

The condition is most noticeable when attempting to transmit via two channels (B1 and B2) to achieve a transmission rate of 128kbps. The COM port speed will be set to 115.2kbps through the communication software (for example. Dial-Up Networking for Microsoft Windows 95).

Affected configurations
  • IBM PC300/700, series 65x7, 68x7, 6589
  • IBM PC300XL, series 6588
  • IntelliStation Z Pro, series 6899
  • PC Server 310 model, 8639-0Ex
  • PC Server 315 models, 8638-PSx / PJx / KJx / KSx
Solution

This is not a defect. do not replace system hardware.

The systems mentioned above meet all design specifications and operating performance requirements. This condition is a design characteristic of the serial transceiver chip used in the above PC 300/700 and PC Server 310/315 series systems.

If the customer requires high speed ISDN communications (e.g 128kbps), either of the following recommendations should be considered. Each of the following has been tested and is supported for high speed ISDN communication rates in the PC 300/700 and PC Server 310/315 series systems.

  1. Use of an internal ISDN modem.
  2. Use of a serial adapter card designed to accommodate high ISDN transmission speeds.
  3. If additional assistance is required, contact your local IBM Support Center.

Document Location

Worldwide

Operating System

IntelliStation Pro:All operating systems listed

Older System x:Operating system independent / None

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Document Information

Modified date:
29 January 2019

UID

ibm1MIGR-59803

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