Appendix B. Duplex Mode (Optional)
Duplexing is a performance option that lets you choose how the adapter sends and
receives data packets over the network. The adapter can operate at full duplex only
when connected to a full-duplex 10BASE-T or 100BASE-TX switch, or to another
full-duplex adapter.
The possible settings for duplexing are:
v
Auto (requires a full-duplex adapter or switch with auto-negotiation capability).
The adapter 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 adapter runs at half duplex.
v
Full duplex (requires a full-duplex switch or adapter). The adapter can send and
receive packets at the same time. This mode can increase adapter performance
capability. If the full-duplex switch provides autonegotiation, the adapter runs at
full duplex. If the full-duplex switch does not provide auto-negotiation, you need
to set the adapter duplex mode manually (see the following sections), because it
defaults to half duplex.
v
Half duplex. The adapter performs one operation at a time; it either sends or
receives.
Note: If an adapter is running at 100 Mbps and half duplex, your potential
bandwidth is higher than if you run it at 10 Mbps and full duplex.
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, many
currently-installed switches do not 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 that you are loading for your network operating
system.
To set up the duplex mode, see the section that corresponds to your operating
system.
Attention: Adapter performance may suffer or your adapter may not operate if your
switch does not support full duplex and you configure the adapter to full duplex. The
switch settings must always agree with the adapter.
Also, make sure that you always set the speed when you configure duplex.
Setting Full Duplex in DOS, ODI, NDIS 2.01 Clients
For each adapter, edit the NET.CFG or PROTOCOL.INI file. If you edit the
NET.CFG file, add the following keywords to the Link Driver section. For the
PROTOCOL.INI file, add the keywords anywhere:
FORCEDUPLEX 2
SPEED 100 (or 10 if 10BASE-T)
© Copyright IBM Corp. 1998, 1999
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