EM(4)							   BSD Kernel Interfaces Manual 						     EM(4)

NAME
     em -- Intel(R) PRO/1000 Gigabit Ethernet adapter driver

SYNOPSIS
     To compile this driver into the kernel, place the following line in your kernel configuration file:

	   device em

     Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

	   if_em_load="YES"

DESCRIPTION
     The em driver provides support for PCI Gigabit Ethernet adapters based on the Intel 82540, 82541ER, 82541PI, 82542, 82543, 82544, 82545,
     82546, 82546EB, 82546GB, 82547, 82571, 81572, 82573, and 82574 Ethernet controller chips.	The driver supports Transmit/Receive checksum off-
     load and Jumbo Frames on all but 82542-based adapters.  Furthermore it supports TCP segmentation offload (TSO) on all adapters but those
     based on the 82543, 82544 and 82547 controller chips.  The identification LEDs of the adapters supported by the em driver can be controlled
     via the led(4) API for localization purposes.  For further hardware information, see the README included with the driver.

     For questions related to hardware requirements, refer to the documentation supplied with your Intel PRO/1000 adapter.  All hardware require-
     ments listed apply to use with FreeBSD.

     Support for Jumbo Frames is provided via the interface MTU setting.  Selecting an MTU larger than 1500 bytes with the ifconfig(8) utility
     configures the adapter to receive and transmit Jumbo Frames.  The maximum MTU size for Jumbo Frames is 16114.

     This driver version supports VLANs.  The em driver supports the following media types:

     autoselect   Enables auto-negotiation for speed and duplex.

     10baseT/UTP  Sets 10Mbps operation.  Use the mediaopt option to select full-duplex mode.

     100baseTX	  Sets 100Mbps operation.  Use the mediaopt option to select full-duplex mode.

     1000baseSX   Sets 1000Mbps operation.  Only full-duplex mode is supported at this speed.

     1000baseTX   Sets 1000Mbps operation.  Only full-duplex mode is supported at this speed.

     The em driver supports the following media options:

     full-duplex  Forces full-duplex operation

     half-duplex  Forces half-duplex operation.

     Only use mediaopt to set the driver to full-duplex.  If mediaopt is not specified, the driver defaults to half-duplex.

     For more information on configuring this device, see ifconfig(8).

HARDWARE
     The em driver supports Gigabit Ethernet adapters based on the Intel 82540, 82541ER, 82541PI, 82542, 82543, 82544, 82545, 82546, 82546EB,
     82546GB, 82547, 82571, 82572, 82573, and 82574 controller chips:

     o	 Intel PRO/1000 CT Network Connection (82547)
     o	 Intel PRO/1000 F Server Adapter (82543)
     o	 Intel PRO/1000 Gigabit Server Adapter (82542)
     o	 Intel PRO/1000 GT Desktop Adapter (82541PI)
     o	 Intel PRO/1000 MF Dual Port Server Adapter (82546)
     o	 Intel PRO/1000 MF Server Adapter (82545)
     o	 Intel PRO/1000 MF Server Adapter (LX) (82545)
     o	 Intel PRO/1000 MT Desktop Adapter (82540)
     o	 Intel PRO/1000 MT Desktop Adapter (82541)
     o	 Intel PRO/1000 MT Dual Port Server Adapter (82546)
     o	 Intel PRO/1000 MT Quad Port Server Adapter (82546EB)
     o	 Intel PRO/1000 MT Server Adapter (82545)
     o	 Intel PRO/1000 PF Dual Port Server Adapter (82571)
     o	 Intel PRO/1000 PF Quad Port Server Adapter (82571)
     o	 Intel PRO/1000 PF Server Adapter (82572)
     o	 Intel PRO/1000 PT Desktop Adapter (82572)
     o	 Intel PRO/1000 PT Dual Port Server Adapter (82571)
     o	 Intel PRO/1000 PT Quad Port Server Adapter (82571)
     o	 Intel PRO/1000 PT Server Adapter (82572)
     o	 Intel PRO/1000 T Desktop Adapter (82544)
     o	 Intel PRO/1000 T Server Adapter (82543)
     o	 Intel PRO/1000 XF Server Adapter (82544)
     o	 Intel PRO/1000 XT Server Adapter (82544)

LOADER TUNABLES
     Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5).

     hw.em.rxd
	     Number of receive descriptors allocated by the driver.  The default value is 256.	The 82542 and 82543-based adapters can handle up
	     to 256 descriptors, while others can have up to 4096.

     hw.em.txd
	     Number of transmit descriptors allocated by the driver.  The default value is 256.  The 82542 and 82543-based adapters can handle up
	     to 256 descriptors, while others can have up to 4096.

     hw.em.rx_int_delay
	     This value delays the generation of receive interrupts in units of 1.024 microseconds.  The default value is 0, since adapters may
	     hang with this feature being enabled.

     hw.em.rx_abs_int_delay
	     If hw.em.rx_int_delay is non-zero, this tunable limits the maximum delay in which a receive interrupt is generated.

     hw.em.tx_int_delay
	     This value delays the generation of transmit interrupts in units of 1.024 microseconds.  The default value is 64.

     hw.em.tx_abs_int_delay
	     If hw.em.tx_int_delay is non-zero, this tunable limits the maximum delay in which a transmit interrupt is generated.

DIAGNOSTICS
     em%d: Unable to allocate bus resource: memory  A fatal initialization error has occurred.

     em%d: Unable to allocate bus resource: interrupt  A fatal initialization error has occurred.

     em%d: watchdog timeout -- resetting  The device has stopped responding to the network, or there is a problem with the network connection
     (cable).

SUPPORT
     For general information and support, go to the Intel support website at: http://support.intel.com.

     If an issue is identified with the released source code on the supported kernel with a supported adapter, email the specific information
     related to the issue to <freebsdnic@mailbox.intel.com>.

FILES
     /dev/led/em*  identification LED device nodes

EXAMPLES
     Make the identification LED of em0 blink:

	   echo f2 > /dev/led/em0

     Turn the identification LED of em0 off again:

	   echo 0 > /dev/led/em0

SEE ALSO
     altq(4), arp(4), igb(4), led(4), netintro(4), ng_ether(4), polling(4), vlan(4), ifconfig(8)

HISTORY
     The em device driver first appeared in FreeBSD 4.4.

AUTHORS
     The em driver was written by Intel Corporation <freebsdnic@mailbox.intel.com>.

BUGS
     Hardware-assisted VLAN processing is disabled by default.	You can enable it on an em interface using ifconfig(8).

BSD								   May 14, 2010 							       BSD