Troubleshooting Macintoshes for Disconnects

Testing the Line

You can determine whether your problem is related to a software conflict or a line noise problem by using a dedicated data comminucations program (i.e. Zterm,Microphone, etc.) and logging into our shell. If you are able to maintain a connection, then disconnects possibly reflect some conflict between MacPPP and your system. If you are unable to maintain a connection you may be experiencing line noise problems. If you need a copy of Zterm for this test you can find it here.

Modem Init Strings

The correct modem init string is very important. Check your manual for a Hardware Handshaking factory default, or click
here for a list of manufacturer-recommended strings by modem type. Try adding S10=20 at the end of the recommended string to make it hang on the line during loud line bursts. You can increase this number up to 255 although I wouldn't recommend much above 100.

Extensions, etc.

Extensions and Control Panels that are not a part of the standard Apple operating system can cause conflicts with data communications - especially complex packages like MacPPP. System 7.5 has an extensions manager that should allow you to restart with "System 7.5 Only." Try choosing this option and install nothing extra except the Config PPP Control Panel and the PPP extension. For System 7.0 or 7.1 you may have to accomplish this manually.


It is possible that a connection problem could be resolved by upgrading to a newer dialler. You may wish to start with the latest dialler from Steve Dagley, FreePPP 1.0.4 This program behaves similarly to MacPPP, although if you are using $USERID$ and $PASSWORD$ on the connect script, you'll have to replace those with your username and password.

Port Speed

Try reducing your Port Speed one choice at a time. If the Port Speed is equal to or less than the speed of the modem, disable data compression in your modem init string. Check your modem manual (for example, USR uses &K0; to disable data compression). If any of these low speeds work, this may reflect other conflicts between your modem and MacPPP. Try upgrading to FreePPP, or try restarting your machine with system extensions and control panels only, plus the PPP extension and Config PPP control panel.

Flow Control

Use of flow control can greatly affect connections in MacPPP. Start with full flow control (CTS &RTS;). Some sources recommend CTS Only for any port speed over 9600. Use None if the port speed is equal to or less than the modem speed. Variations of Port Speed and Flow Control can lead to a connection that works best with your Macintosh and modem. Many modem manufacturers recommend using CTS Only as a flow control option. Your modem's technical support department may have specific recommendations for you should you choose to contact them.