The PCI 10/100Base-TX/3000 product provides the means for interfacing various
types of HP e3000 systems to either a 10Base-T or 100Base-TX network.
100Base-TX is a subset of 100Base-T networking defined by the IEEE 802.3u-1995
standard. 100Base-TX provides 100 Mbits/s data transmission over category 5
unshielded twisted-pair (UTP) cable for which two pairs of wires in the cable
are used — one wire pair for receiving data, and one wire pair for
transmitting data. The same card port that supports 100Base-TX operation can
also support 10Base-T operation.
Autonegotiation is a mechanism defined in the IEEE 802.3u specification whereby
devices sharing a link segment can exchange information while the link is being
established and automatically configure themselves to operate at the most
efficient mode shared between them.
Autonegotiation is like a rotary switch that automatically switches to the
correct technology such as 10Base-T or 100Base-TX or between half- and
full-duplex modes. Once the most efficient common mode is determined,
autonegotiation passes control of the link to the appropriate technology, sets
the appropriate duplex mode, and then becomes transparent until the link is
broken.
The following is the IEEE 802.3u-defined autonegotiation hierarchy for
resolving multiple common abilities for a 10/100Base-TX card:
100Base-TX full-duplex (most efficient)
100Base-TX half-duplex
10Base-T full-duplex
10Base-T half-duplex (least efficient)
For example, if both devices on the link support 10Base-T (half-duplex) and
100Base-TX (half-duplex), autonegotiation at both ends will select 100Base-TX
(half-duplex) instead of 10Base-T (half-duplex).
Many 100Base-TX devices on the market today such as hubs and switches do not
support autonegotiation. Either the speed and duplex mode of the device are
fixed (as is usually the case with hubs), or they are often manually configured
at the desired speed and duplex (as is often the case for switches). However,
switches that support autonegotiation are becoming more commonplace.
If the PCI 10/100Base-TX/3000 card is connected to a device, such as a switch,
that is autonegotiating, the PCI card will autonegotiate with the device to
mutually determine the highest possible speed and duplex settings between them.
If the PCI 10/100Base-TX/3000 card is connected to a device that does not
support autonegotiation or a device that has autonegotiation disabled, the PCI
card will autosense the speed of the link and set itself accordingly. The
duplex mode of the card will be set to half-duplex in this case. If you
want the card to operate in full-duplex mode, you must set it using the method
described in "Notes on Manual Speed and Duplex Mode Configuration" in this
document.
The PCI 10/100Base-TX card will sense when the connection between itself and a
hub or switch on the other end of a link has been broken. If a connection is
made to another (or the same) device and autonegotiation is enabled, the
autonegotiation and autosensing process will be done again automatically.
Autonegotiation and autosensing are also done whenever the interface is reset.
Notes on Manual Speed and Duplex Mode Configuration