Intel EtherExpress PRO/100+, Installation Manual

12     Intel EtherExpress PRO/100+ TX PCI LAN Controller User’s Guide

Select Duplex Mode (Optional)

Duplexing is a performance option that lets you choose how the ethernet 
controller sends and receives data packets over the network. The ethernet 
controller can operate at full duplex only when connected to a full duplex 
10BASE-T, 100BASE-TX switch, or another full duplex adapter.

•

Auto (requires a full duplex adapter or switch with auto-
negotiation capability). The controller negotiates with the switch to 
send and receive packets at the highest rate. This is the default 
setting. If the switch does not provide auto-negotiation, the 
controller runs at half duplex.

•

Full duplex (requires a full duplex switch or adapter). The 
controller can send and receive packets at the same time. This 
mode can increase controller performance capability. If the full 
duplex switch provides auto-negotiation, the controller runs at full 
duplex. If the full duplex switch does not provide auto-negotiation, 
you need to set the controller duplex mode manually (see 
following paragraphs), because it defaults to half duplex.

•

Half duplex. The controller performs one operation at a time; it 
either sends or receives. 

Manually Configuring for Full Duplex

If your switch supports auto-negotiation with the N-way standard, duplex 
configuration is automatic and no action is required on your part. However, 
few switches in the current installed base support auto-negotiation. Check 
with your network system administrator to verify whether your switch 
supports this feature. Most installations will require manual configuration 
to change to full duplex.

Configuration is specific to the driver you’re loading for your network 
operating system (NOS).

To set up the duplex mode, refer to the section below that corresponds to 
your operating system.

 Note:

If your controller is running 
at 100 Mbps and half 
duplex, your potential 
bandwidth is higher than if 
you run it at 10 Mbps and 
full duplex.

 Note:

Controller performance 
may suffer or your controller 
may not operate if your 
switch doesn’t support full 
duplex and you configure 
the controller to full duplex. 
Make sure you always set 
the speed when you 
configure duplex.

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