It has been verified by experiment that certain auto-negotiating ethernet cards (both in PCs and in Macs), when connected to certain models of cable modem, sense the ethernet duplex setting incorrectly. Such a cable modem has ethernet hardware which is capable of operating only in half-duplex mode, at 10 Mbps, yet some auto-negotiating ethernet cards sense it as full-duplex. If an auto-negotiation card incorrectly starts operating in full-duplex mode, there can be collisions between ethernet packets being transmitted in both directions at the same time, leading to packet loss, and repeated re-transmissions. There is no visible evidence of this apart from poor performance. This problem can be avoided by manually configuring your ethernet card to be 10 Mbps half-duplex. No ill-effects will transpire from doing this, even when it is not necessary. The exact wording of the setting changes required varies from one manufacturer to another, so the instructions below are necessarily rather broadly defined.
To make this change under Win98/ME, follow these steps:
Open Control Panel.
Double-click Network.
From the scrollable list, select your Ethernet adapter (rather than any dial-up) with a green icon.
Click the button Properties.
Click the tab Advanced to bring it to the front:
In the Property box, the property name to be selected varies according to model of ethernet card. Examples are: Network Link Selection, Media Type, Connection Type, Duplex Mode, or any similarly-named property which can have Values looking like Auto-Negotiation, or 10BT, or 10BaseT.
In the Value box, select a value which either (a) explicitly says half-duplex or semi-duplex, or (b) at least does not say full-duplex [e.g. 10BaseT on its own is OK]. If there is a choice between 10 and 100 with half-duplex, choose the 10. Do not choose 10Base5, 10Base2, or AUI.
Click OK to exit the Adapter settings.
Click OK all the way out - you might need to restart.
To make this change under Windows 2000 or XP, follow these steps:
Open Control Panel.
Double-click Network and Dial-up Connections.
Identify the icon for your cable modem connection: usually Local Area Connection.
Right-click that icon and select Properties.
Under the ethernet adapter icon, click the button Configure.
Click the tab Advanced to bring it to the front:
In the Property box, the property name to be selected varies according to model of ethernet card. Examples are: Network Link Selection, Media Type, Connection Type, Duplex Mode, or any similarly-named property which can have Values looking like Auto-Negotiation, or 10BT, or 10BaseT.
In the Value box, select a value which either (a) explicitly says half-duplex or semi-duplex, or (b) at least does not say full-duplex [e.g. 10BaseT on its own is OK]. If there is a choice between 10 and 100 with half-duplex, choose the 10. Do not choose 10Base5, 10Base2, or AUI.
Click OK to exit the Adapter settings.
Click OK to exit the Connection properties
