Duplexing is a performance option that lets you choose how an adapter sends and receives packets over the network.

Auto (TX adapter only):
The TX adapter negotiates with the full duplex switching hub to send and receive packets at the highest rate. The hub must support auto-negotiation. If the hub does not support auto-negotiation, the adapter defaults to half duplex.

Full duplex (requires full-duplex switching hub):
The adapter sends and receives packets simultaneously by using a different wire to perform each function. This feature can improve adapter performance by eliminating collisions. Note that the PRO/100 T4 adapter supports full duplex at 10 Mbps only.

Half duplex:
The adapter performs one operation at a time (because send and receive lines are shared); it either sends or receives.

PRO/100B T4 adapter duplex choices: Full duplex (requires 10 Mpbs 10BASE-T full-duplex switching hub):
The T4 adapter sends and receives packets simultaneously by using a different wire to perform each function. This feature can improve adapter performance by eliminating collisions. Note that the PRO/100 T4 adapter supports full duplex at 10 Mbps only, and requires a 10BASE-T switching hub.

Half duplex:
The adapter performs one operation at a time (because send and receive lines are shared); it either sends or receives.

Warning: Incorrectly forcing a specific duplex mode may result in poor performance. Consult your LAN administrator before forcing a duplex mode or if you don't know what kind of hub you're attached to.

Full duplex mode is available using the following configurations:

PRO/100B TX adapter (10 or 100 Mbps w/ 100BASE-TX hub)

PRO/100B T4 adapter (10 Mbps only w/ 10BASE-T hub)

Configuring for full-duplex

PRO/100B TX adapter:
If you have an auto-negotiating hub (an NWay* hub), the Intel PRO/100B PCI TX adapter will automatically match the duplex setting at the hub. If you don't have an auto-negotiating hub, you'll need to manually configure the adapter for full duplex support.

PRO/100B T4 adapter:
The T4 adapter does not support auto-negotiation.

PRO/100B TX and T4 adapters:
Configuration is specific to the driver you're loading for your network operating system (NOS). See the sections for your NOS below.

Note: If you're using the PRO/100B TX or T4 adapter, you must set the Speed when configuring for full-duplex support. Don't leave the Speed set to Auto.

To set up the duplex mode, refer to the section below that corresponds to your operating system. For example, if you're running Windows NT* on a Novell* network, choose the Windows NT* method below.

Note that performance may suffer if your hub is not full duplex and you configure the adapter to full duplex. Leave the adapter on half duplex if you are not sure what type of hub you are connected to.

DOS/ODI clients
Edit the NET.CFG file. Add the SPEED and FORCEDUPLEX parameters under the link driver section. For example:

Link Driver E100BODI

SPEED 100 (or 10 for 10 Mbps operation)

FORCEDUPLEX 2

Windows NT*
Use the PRO Adapter setup program:

1. Double-click the PROSet icon in the Control Panel.
   
   
2. Click Change.
   
   
3. Set Speed on PRO/100 TX to 10 or 100. On PRO/100 T4 adapter, set to 10.
   
   
4. Set Duplex Mode to Full.
   
   
5. Click OK until prompted to restart.
   
6. Restart Windows NT.
   

Windows 95*
Use the PRO Adapter setup program:

1. Double-click the PROSet icon in the Control Panel.
   
   
2. Click Change.
   
   
3. Set Speed on PRO/100 TX to 10 or 100. On PRO/100 T4 adapter, set to 10.
   
   
4. Set Duplex Mode to Full.
   
   
5. Click OK until prompted to restart.
   
6. Restart Windows 95.

Other NDIS 2.x based clients
Edit the PROTOCOL.INI file. Add the FORCEDUPLEX and SPEED parameters to the E100B section. For example:

[E100B_NIF] SPEED = 100 FORCEDUPLEX = 2

; varies depending on your NOS ; or 10 for 10 Mbps operation

This applies to:

Intel® PRO/100B Adapter