Most 100BASE-TX Ethernet Adapters can detect when listening for collisions is not required with a process known as auto-negotiation and will operate in a full duplex mode when it is permitted. It hardwires the Ethernet transmitter on one computer to the receiver on the other. A crossover cable doesn't have a collision problem. Two computers can be connected directly together in an Ethernet with a crossover cable.

The affect on a small, 100 Mbps (million bits per scond), 5-port network is not as significant. In a 10 Mhz 10Base-T network the affect is to slow the network to nearly a crawl. The result is when a person using a computer on a hub downloads a large file or group of files from another computer the network becomes congested. Because they have to operate at half duplex (data flows one way at a time) and a hub retransmits data from one PC to all of the PCs, the maximum bandwidth is 100 Mhz and that bandwidth is shared by all of the PC's connected to the hub. If the adapters didn't have to listen with their receivers for collisions they would be able to send data at the same time they are receiving it (full duplex). Each Ethernet Adapter has both a receiver and a transmitter. The process is prescribed in the Ethernet Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol. When that happens all of the PCs have to go though a routine to resolve the conflict. If two or more PCs on the network try to send packets at the same time a collision is said to occur. When a hub receives a packet (chunk) of data (a frame in Ethernet lingo) at one of its ports from a PC on the network, it transmits (repeats) the packet to all of its ports and, thus, to all of the other PCs on the network. Although hubs and switches both glue the PCs in a network together, a switch is more expensive and a network built with switches is generally considered faster than one built with hubs.

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