Documentation/networking/e1000.txt - kernel/bruno - Git at Google

 Linux* Base Driver for Intel(R) Ethernet Network Connection
 ===========================================================

 Intel Gigabit Linux driver.
 Copyright(c) 1999 - 2013 Intel Corporation.

 Contents
 ========

 - Identifying Your Adapter
 - Command Line Parameters
 - Speed and Duplex Configuration
 - Additional Configurations
 - Support

 Identifying Your Adapter
 ========================

 For more information on how to identify your adapter, go to the Adapter &
 Driver ID Guide at:

     http://support.intel.com/support/go/network/adapter/idguide.htm

 For the latest Intel network drivers for Linux, refer to the following
 website.  In the search field, enter your adapter name or type, or use the
 networking link on the left to search for your adapter:

     http://support.intel.com/support/go/network/adapter/home.htm

 Command Line Parameters
 =======================

 The default value for each parameter is generally the recommended setting,
 unless otherwise noted.

 NOTES:  For more information about the AutoNeg, Duplex, and Speed
         parameters, see the "Speed and Duplex Configuration" section in
         this document.

         For more information about the InterruptThrottleRate,
         RxIntDelay, TxIntDelay, RxAbsIntDelay, and TxAbsIntDelay
         parameters, see the application note at:
         http://www.intel.com/design/network/applnots/ap450.htm

 AutoNeg
 -------
 (Supported only on adapters with copper connections)
 Valid Range:   0x01-0x0F, 0x20-0x2F
 Default Value: 0x2F

 This parameter is a bit-mask that specifies the speed and duplex settings
 advertised by the adapter.  When this parameter is used, the Speed and
 Duplex parameters must not be specified.

 NOTE:  Refer to the Speed and Duplex section of this readme for more
        information on the AutoNeg parameter.

 Duplex
 ------
 (Supported only on adapters with copper connections)
 Valid Range:   0-2 (0=auto-negotiate, 1=half, 2=full)
 Default Value: 0

 This defines the direction in which data is allowed to flow.  Can be
 either one or two-directional.  If both Duplex and the link partner are
 set to auto-negotiate, the board auto-detects the correct duplex.  If the
 link partner is forced (either full or half), Duplex defaults to half-
 duplex.

 FlowControl
 -----------
 Valid Range:   0-3 (0=none, 1=Rx only, 2=Tx only, 3=Rx&Tx)
 Default Value: Reads flow control settings from the EEPROM

 This parameter controls the automatic generation(Tx) and response(Rx)
 to Ethernet PAUSE frames.

 InterruptThrottleRate
 ---------------------
 (not supported on Intel(R) 82542, 82543 or 82544-based adapters)
 Valid Range:   0,1,3,4,100-100000 (0=off, 1=dynamic, 3=dynamic conservative,
                                  4=simplified balancing)
 Default Value: 3

 The driver can limit the amount of interrupts per second that the adapter
 will generate for incoming packets. It does this by writing a value to the
 adapter that is based on the maximum amount of interrupts that the adapter
 will generate per second.

 Setting InterruptThrottleRate to a value greater or equal to 100
 will program the adapter to send out a maximum of that many interrupts
 per second, even if more packets have come in. This reduces interrupt
 load on the system and can lower CPU utilization under heavy load,
 but will increase latency as packets are not processed as quickly.

 The default behaviour of the driver previously assumed a static
 InterruptThrottleRate value of 8000, providing a good fallback value for
 all traffic types,but lacking in small packet performance and latency.
 The hardware can handle many more small packets per second however, and
 for this reason an adaptive interrupt moderation algorithm was implemented.

 Since 7.3.x, the driver has two adaptive modes (setting 1 or 3) in which
 it dynamically adjusts the InterruptThrottleRate value based on the traffic
 that it receives. After determining the type of incoming traffic in the last
 timeframe, it will adjust the InterruptThrottleRate to an appropriate value
 for that traffic.

 The algorithm classifies the incoming traffic every interval into
 classes.  Once the class is determined, the InterruptThrottleRate value is
 adjusted to suit that traffic type the best. There are three classes defined:
 "Bulk traffic", for large amounts of packets of normal size; "Low latency",
 for small amounts of traffic and/or a significant percentage of small
 packets; and "Lowest latency", for almost completely small packets or
 minimal traffic.

 In dynamic conservative mode, the InterruptThrottleRate value is set to 4000
 for traffic that falls in class "Bulk traffic". If traffic falls in the "Low
 latency" or "Lowest latency" class, the InterruptThrottleRate is increased
 stepwise to 20000. This default mode is suitable for most applications.

 For situations where low latency is vital such as cluster or
 grid computing, the algorithm can reduce latency even more when
 InterruptThrottleRate is set to mode 1. In this mode, which operates
 the same as mode 3, the InterruptThrottleRate will be increased stepwise to
 70000 for traffic in class "Lowest latency".

 In simplified mode the interrupt rate is based on the ratio of TX and
 RX traffic.  If the bytes per second rate is approximately equal, the
 interrupt rate will drop as low as 2000 interrupts per second.  If the
 traffic is mostly transmit or mostly receive, the interrupt rate could
 be as high as 8000.

 Setting InterruptThrottleRate to 0 turns off any interrupt moderation
 and may improve small packet latency, but is generally not suitable
 for bulk throughput traffic.

 NOTE:  InterruptThrottleRate takes precedence over the TxAbsIntDelay and
        RxAbsIntDelay parameters.  In other words, minimizing the receive
        and/or transmit absolute delays does not force the controller to
        generate more interrupts than what the Interrupt Throttle Rate
        allows.

 CAUTION:  If you are using the Intel(R) PRO/1000 CT Network Connection
           (controller 82547), setting InterruptThrottleRate to a value
           greater than 75,000, may hang (stop transmitting) adapters
           under certain network conditions.  If this occurs a NETDEV
           WATCHDOG message is logged in the system event log.  In
           addition, the controller is automatically reset, restoring
           the network connection.  To eliminate the potential for the
           hang, ensure that InterruptThrottleRate is set no greater
           than 75,000 and is not set to 0.

 NOTE:  When e1000 is loaded with default settings and multiple adapters
        are in use simultaneously, the CPU utilization may increase non-
        linearly.  In order to limit the CPU utilization without impacting
        the overall throughput, we recommend that you load the driver as
        follows:

            modprobe e1000 InterruptThrottleRate=3000,3000,3000

        This sets the InterruptThrottleRate to 3000 interrupts/sec for
        the first, second, and third instances of the driver.  The range
        of 2000 to 3000 interrupts per second works on a majority of
        systems and is a good starting point, but the optimal value will
        be platform-specific.  If CPU utilization is not a concern, use
        RX_POLLING (NAPI) and default driver settings.

 RxDescriptors
 -------------
 Valid Range:   80-256 for 82542 and 82543-based adapters
                80-4096 for all other supported adapters
 Default Value: 256

 This value specifies the number of receive buffer descriptors allocated
 by the driver.  Increasing this value allows the driver to buffer more
 incoming packets, at the expense of increased system memory utilization.

 Each descriptor is 16 bytes.  A receive buffer is also allocated for each
 descriptor and can be either 2048, 4096, 8192, or 16384 bytes, depending
 on the MTU setting. The maximum MTU size is 16110.

 NOTE:  MTU designates the frame size.  It only needs to be set for Jumbo
        Frames.  Depending on the available system resources, the request
        for a higher number of receive descriptors may be denied.  In this
        case, use a lower number.

 RxIntDelay
 ----------
 Valid Range:   0-65535 (0=off)
 Default Value: 0

 This value delays the generation of receive interrupts in units of 1.024
 microseconds.  Receive interrupt reduction can improve CPU efficiency if
 properly tuned for specific network traffic.  Increasing this value adds
 extra latency to frame reception and can end up decreasing the throughput
 of TCP traffic.  If the system is reporting dropped receives, this value
 may be set too high, causing the driver to run out of available receive
 descriptors.

 CAUTION:  When setting RxIntDelay to a value other than 0, adapters may
           hang (stop transmitting) under certain network conditions.  If
           this occurs a NETDEV WATCHDOG message is logged in the system
           event log.  In addition, the controller is automatically reset,
           restoring the network connection.  To eliminate the potential
           for the hang ensure that RxIntDelay is set to 0.

 RxAbsIntDelay
 -------------
 (This parameter is supported only on 82540, 82545 and later adapters.)
 Valid Range:   0-65535 (0=off)
 Default Value: 128

 This value, in units of 1.024 microseconds, limits the delay in which a
 receive interrupt is generated.  Useful only if RxIntDelay is non-zero,
 this value ensures that an interrupt is generated after the initial
 packet is received within the set amount of time.  Proper tuning,
 along with RxIntDelay, may improve traffic throughput in specific network
 conditions.

 Speed
 -----
 (This parameter is supported only on adapters with copper connections.)
 Valid Settings: 0, 10, 100, 1000
 Default Value:  0 (auto-negotiate at all supported speeds)

 Speed forces the line speed to the specified value in megabits per second
 (Mbps).  If this parameter is not specified or is set to 0 and the link
 partner is set to auto-negotiate, the board will auto-detect the correct
 speed.  Duplex should also be set when Speed is set to either 10 or 100.

 TxDescriptors
 -------------
 Valid Range:   80-256 for 82542 and 82543-based adapters
                80-4096 for all other supported adapters
 Default Value: 256

 This value is the number of transmit descriptors allocated by the driver.
 Increasing this value allows the driver to queue more transmits.  Each
 descriptor is 16 bytes.

 NOTE:  Depending on the available system resources, the request for a
        higher number of transmit descriptors may be denied.  In this case,
        use a lower number.

 TxDescriptorStep
 ----------------
 Valid Range:    1 (use every Tx Descriptor)
                 4 (use every 4th Tx Descriptor)

 Default Value:  1 (use every Tx Descriptor)

 On certain non-Intel architectures, it has been observed that intense TX
 traffic bursts of short packets may result in an improper descriptor
 writeback. If this occurs, the driver will report a "TX Timeout" and reset
 the adapter, after which the transmit flow will restart, though data may
 have stalled for as much as 10 seconds before it resumes.

 The improper writeback does not occur on the first descriptor in a system
 memory cache-line, which is typically 32 bytes, or 4 descriptors long.

 Setting TxDescriptorStep to a value of 4 will ensure that all TX descriptors
 are aligned to the start of a system memory cache line, and so this problem
 will not occur.

 NOTES: Setting TxDescriptorStep to 4 effectively reduces the number of
        TxDescriptors available for transmits to 1/4 of the normal allocation.
        This has a possible negative performance impact, which may be
        compensated for by allocating more descriptors using the TxDescriptors
        module parameter.

        There are other conditions which may result in "TX Timeout", which will
        not be resolved by the use of the TxDescriptorStep parameter. As the
        issue addressed by this parameter has never been observed on Intel
        Architecture platforms, it should not be used on Intel platforms.

 TxIntDelay
 ----------
 Valid Range:   0-65535 (0=off)
 Default Value: 64

 This value delays the generation of transmit interrupts in units of
 1.024 microseconds.  Transmit interrupt reduction can improve CPU
 efficiency if properly tuned for specific network traffic.  If the
 system is reporting dropped transmits, this value may be set too high
 causing the driver to run out of available transmit descriptors.

 TxAbsIntDelay
 -------------
 (This parameter is supported only on 82540, 82545 and later adapters.)
 Valid Range:   0-65535 (0=off)
 Default Value: 64

 This value, in units of 1.024 microseconds, limits the delay in which a
 transmit interrupt is generated.  Useful only if TxIntDelay is non-zero,
 this value ensures that an interrupt is generated after the initial
 packet is sent on the wire within the set amount of time.  Proper tuning,
 along with TxIntDelay, may improve traffic throughput in specific
 network conditions.

 XsumRX
 ------
 (This parameter is NOT supported on the 82542-based adapter.)
 Valid Range:   0-1
 Default Value: 1

 A value of '1' indicates that the driver should enable IP checksum
 offload for received packets (both UDP and TCP) to the adapter hardware.

 Copybreak
 ---------
 Valid Range:   0-xxxxxxx (0=off)
 Default Value: 256
 Usage: insmod e1000.ko copybreak=128

 Driver copies all packets below or equaling this size to a fresh RX
 buffer before handing it up the stack.

 This parameter is different than other parameters, in that it is a
 single (not 1,1,1 etc.) parameter applied to all driver instances and
 it is also available during runtime at
 /sys/module/e1000/parameters/copybreak

 SmartPowerDownEnable
 --------------------
 Valid Range: 0-1
 Default Value:  0 (disabled)

 Allows PHY to turn off in lower power states. The user can turn off
 this parameter in supported chipsets.

 KumeranLockLoss
 ---------------
 Valid Range: 0-1
 Default Value: 1 (enabled)

 This workaround skips resetting the PHY at shutdown for the initial
 silicon releases of ICH8 systems.

 Speed and Duplex Configuration
 ==============================

 Three keywords are used to control the speed and duplex configuration.
 These keywords are Speed, Duplex, and AutoNeg.

 If the board uses a fiber interface, these keywords are ignored, and the
 fiber interface board only links at 1000 Mbps full-duplex.

 For copper-based boards, the keywords interact as follows:

   The default operation is auto-negotiate.  The board advertises all
   supported speed and duplex combinations, and it links at the highest
   common speed and duplex mode IF the link partner is set to auto-negotiate.

   If Speed = 1000, limited auto-negotiation is enabled and only 1000 Mbps
   is advertised (The 1000BaseT spec requires auto-negotiation.)

   If Speed = 10 or 100, then both Speed and Duplex should be set.  Auto-
   negotiation is disabled, and the AutoNeg parameter is ignored.  Partner
   SHOULD also be forced.

 The AutoNeg parameter is used when more control is required over the
 auto-negotiation process.  It should be used when you wish to control which
 speed and duplex combinations are advertised during the auto-negotiation
 process.

 The parameter may be specified as either a decimal or hexadecimal value as
 determined by the bitmap below.

 Bit position   7      6      5       4       3      2      1       0
 Decimal Value  128    64     32      16      8      4      2       1
 Hex value      80     40     20      10      8      4      2       1
 Speed (Mbps)   N/A    N/A    1000    N/A     100    100    10      10
 Duplex                       Full            Full   Half   Full    Half

 Some examples of using AutoNeg:

   modprobe e1000 AutoNeg=0x01 (Restricts autonegotiation to 10 Half)
   modprobe e1000 AutoNeg=1 (Same as above)
   modprobe e1000 AutoNeg=0x02 (Restricts autonegotiation to 10 Full)
   modprobe e1000 AutoNeg=0x03 (Restricts autonegotiation to 10 Half or 10 Full)
   modprobe e1000 AutoNeg=0x04 (Restricts autonegotiation to 100 Half)
   modprobe e1000 AutoNeg=0x05 (Restricts autonegotiation to 10 Half or 100
   Half)
   modprobe e1000 AutoNeg=0x020 (Restricts autonegotiation to 1000 Full)
   modprobe e1000 AutoNeg=32 (Same as above)

 Note that when this parameter is used, Speed and Duplex must not be specified.

 If the link partner is forced to a specific speed and duplex, then this
 parameter should not be used.  Instead, use the Speed and Duplex parameters
 previously mentioned to force the adapter to the same speed and duplex.

 Additional Configurations
 =========================

   Jumbo Frames
   ------------
   Jumbo Frames support is enabled by changing the MTU to a value larger than
   the default of 1500.  Use the ifconfig command to increase the MTU size.
   For example:

        ifconfig eth<x> mtu 9000 up

   This setting is not saved across reboots.  It can be made permanent if
   you add:

        MTU=9000

    to the file /etc/sysconfig/network-scripts/ifcfg-eth<x>.  This example
    applies to the Red Hat distributions; other distributions may store this
    setting in a different location.

   Notes:
   Degradation in throughput performance may be observed in some Jumbo frames
   environments. If this is observed, increasing the application's socket buffer
   size and/or increasing the /proc/sys/net/ipv4/tcp_*mem entry values may help.
   See the specific application manual and /usr/src/linux*/Documentation/
   networking/ip-sysctl.txt for more details.

   - The maximum MTU setting for Jumbo Frames is 16110.  This value coincides
     with the maximum Jumbo Frames size of 16128.

   - Using Jumbo frames at 10 or 100 Mbps is not supported and may result in
     poor performance or loss of link.

   - Adapters based on the Intel(R) 82542 and 82573V/E controller do not
     support Jumbo Frames. These correspond to the following product names:
      Intel(R) PRO/1000 Gigabit Server Adapter
      Intel(R) PRO/1000 PM Network Connection

   ethtool
   -------
   The driver utilizes the ethtool interface for driver configuration and
   diagnostics, as well as displaying statistical information.  The ethtool
   version 1.6 or later is required for this functionality.

   The latest release of ethtool can be found from
   http://ftp.kernel.org/pub/software/network/ethtool/

   Enabling Wake on LAN* (WoL)
   ---------------------------
   WoL is configured through the ethtool* utility.

   WoL will be enabled on the system during the next shut down or reboot.
   For this driver version, in order to enable WoL, the e1000 driver must be
   loaded when shutting down or rebooting the system.

 Support
 =======

 For general information, go to the Intel support website at:

     http://support.intel.com

 or the Intel Wired Networking project hosted by Sourceforge at:

     http://sourceforge.net/projects/e1000

 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 e1000-devel@lists.sf.net
	Linux* Base Driver for Intel(R) Ethernet Network Connection
	===========================================================

	Intel Gigabit Linux driver.
	Copyright(c) 1999 - 2013 Intel Corporation.

	Contents
	========

	- Identifying Your Adapter
	- Command Line Parameters
	- Speed and Duplex Configuration
	- Additional Configurations
	- Support

	Identifying Your Adapter
	========================

	For more information on how to identify your adapter, go to the Adapter &
	Driver ID Guide at:

	http://support.intel.com/support/go/network/adapter/idguide.htm

	For the latest Intel network drivers for Linux, refer to the following
	website. In the search field, enter your adapter name or type, or use the
	networking link on the left to search for your adapter:

	http://support.intel.com/support/go/network/adapter/home.htm

	Command Line Parameters
	=======================

	The default value for each parameter is generally the recommended setting,
	unless otherwise noted.

	NOTES: For more information about the AutoNeg, Duplex, and Speed
	parameters, see the "Speed and Duplex Configuration" section in
	this document.

	For more information about the InterruptThrottleRate,
	RxIntDelay, TxIntDelay, RxAbsIntDelay, and TxAbsIntDelay
	parameters, see the application note at:
	http://www.intel.com/design/network/applnots/ap450.htm

	AutoNeg
	-------
	(Supported only on adapters with copper connections)
	Valid Range: 0x01-0x0F, 0x20-0x2F
	Default Value: 0x2F

	This parameter is a bit-mask that specifies the speed and duplex settings
	advertised by the adapter. When this parameter is used, the Speed and
	Duplex parameters must not be specified.

	NOTE: Refer to the Speed and Duplex section of this readme for more
	information on the AutoNeg parameter.

	Duplex
	------
	(Supported only on adapters with copper connections)
	Valid Range: 0-2 (0=auto-negotiate, 1=half, 2=full)
	Default Value: 0

	This defines the direction in which data is allowed to flow. Can be
	either one or two-directional. If both Duplex and the link partner are
	set to auto-negotiate, the board auto-detects the correct duplex. If the
	link partner is forced (either full or half), Duplex defaults to half-
	duplex.

	FlowControl
	-----------
	Valid Range: 0-3 (0=none, 1=Rx only, 2=Tx only, 3=Rx&Tx)
	Default Value: Reads flow control settings from the EEPROM

	This parameter controls the automatic generation(Tx) and response(Rx)
	to Ethernet PAUSE frames.

	InterruptThrottleRate
	---------------------
	(not supported on Intel(R) 82542, 82543 or 82544-based adapters)
	Valid Range: 0,1,3,4,100-100000 (0=off, 1=dynamic, 3=dynamic conservative,
	4=simplified balancing)
	Default Value: 3

	The driver can limit the amount of interrupts per second that the adapter
	will generate for incoming packets. It does this by writing a value to the
	adapter that is based on the maximum amount of interrupts that the adapter
	will generate per second.

	Setting InterruptThrottleRate to a value greater or equal to 100
	will program the adapter to send out a maximum of that many interrupts
	per second, even if more packets have come in. This reduces interrupt
	load on the system and can lower CPU utilization under heavy load,
	but will increase latency as packets are not processed as quickly.

	The default behaviour of the driver previously assumed a static
	InterruptThrottleRate value of 8000, providing a good fallback value for
	all traffic types,but lacking in small packet performance and latency.
	The hardware can handle many more small packets per second however, and
	for this reason an adaptive interrupt moderation algorithm was implemented.

	Since 7.3.x, the driver has two adaptive modes (setting 1 or 3) in which
	it dynamically adjusts the InterruptThrottleRate value based on the traffic
	that it receives. After determining the type of incoming traffic in the last
	timeframe, it will adjust the InterruptThrottleRate to an appropriate value
	for that traffic.

	The algorithm classifies the incoming traffic every interval into
	classes. Once the class is determined, the InterruptThrottleRate value is
	adjusted to suit that traffic type the best. There are three classes defined:
	"Bulk traffic", for large amounts of packets of normal size; "Low latency",
	for small amounts of traffic and/or a significant percentage of small
	packets; and "Lowest latency", for almost completely small packets or
	minimal traffic.

	In dynamic conservative mode, the InterruptThrottleRate value is set to 4000
	for traffic that falls in class "Bulk traffic". If traffic falls in the "Low
	latency" or "Lowest latency" class, the InterruptThrottleRate is increased
	stepwise to 20000. This default mode is suitable for most applications.

	For situations where low latency is vital such as cluster or
	grid computing, the algorithm can reduce latency even more when
	InterruptThrottleRate is set to mode 1. In this mode, which operates
	the same as mode 3, the InterruptThrottleRate will be increased stepwise to
	70000 for traffic in class "Lowest latency".

	In simplified mode the interrupt rate is based on the ratio of TX and
	RX traffic. If the bytes per second rate is approximately equal, the
	interrupt rate will drop as low as 2000 interrupts per second. If the
	traffic is mostly transmit or mostly receive, the interrupt rate could
	be as high as 8000.

	Setting InterruptThrottleRate to 0 turns off any interrupt moderation
	and may improve small packet latency, but is generally not suitable
	for bulk throughput traffic.

	NOTE: InterruptThrottleRate takes precedence over the TxAbsIntDelay and
	RxAbsIntDelay parameters. In other words, minimizing the receive
	and/or transmit absolute delays does not force the controller to
	generate more interrupts than what the Interrupt Throttle Rate
	allows.

	CAUTION: If you are using the Intel(R) PRO/1000 CT Network Connection
	(controller 82547), setting InterruptThrottleRate to a value
	greater than 75,000, may hang (stop transmitting) adapters
	under certain network conditions. If this occurs a NETDEV
	WATCHDOG message is logged in the system event log. In
	addition, the controller is automatically reset, restoring
	the network connection. To eliminate the potential for the
	hang, ensure that InterruptThrottleRate is set no greater
	than 75,000 and is not set to 0.

	NOTE: When e1000 is loaded with default settings and multiple adapters
	are in use simultaneously, the CPU utilization may increase non-
	linearly. In order to limit the CPU utilization without impacting
	the overall throughput, we recommend that you load the driver as
	follows:

	modprobe e1000 InterruptThrottleRate=3000,3000,3000

	This sets the InterruptThrottleRate to 3000 interrupts/sec for
	the first, second, and third instances of the driver. The range
	of 2000 to 3000 interrupts per second works on a majority of
	systems and is a good starting point, but the optimal value will
	be platform-specific. If CPU utilization is not a concern, use
	RX_POLLING (NAPI) and default driver settings.

	RxDescriptors
	-------------
	Valid Range: 80-256 for 82542 and 82543-based adapters
	80-4096 for all other supported adapters
	Default Value: 256

	This value specifies the number of receive buffer descriptors allocated
	by the driver. Increasing this value allows the driver to buffer more
	incoming packets, at the expense of increased system memory utilization.

	Each descriptor is 16 bytes. A receive buffer is also allocated for each
	descriptor and can be either 2048, 4096, 8192, or 16384 bytes, depending
	on the MTU setting. The maximum MTU size is 16110.

	NOTE: MTU designates the frame size. It only needs to be set for Jumbo
	Frames. Depending on the available system resources, the request
	for a higher number of receive descriptors may be denied. In this
	case, use a lower number.

	RxIntDelay
	----------
	Valid Range: 0-65535 (0=off)
	Default Value: 0

	This value delays the generation of receive interrupts in units of 1.024
	microseconds. Receive interrupt reduction can improve CPU efficiency if
	properly tuned for specific network traffic. Increasing this value adds
	extra latency to frame reception and can end up decreasing the throughput
	of TCP traffic. If the system is reporting dropped receives, this value
	may be set too high, causing the driver to run out of available receive
	descriptors.

	CAUTION: When setting RxIntDelay to a value other than 0, adapters may
	hang (stop transmitting) under certain network conditions. If
	this occurs a NETDEV WATCHDOG message is logged in the system
	event log. In addition, the controller is automatically reset,
	restoring the network connection. To eliminate the potential
	for the hang ensure that RxIntDelay is set to 0.

	RxAbsIntDelay
	-------------
	(This parameter is supported only on 82540, 82545 and later adapters.)
	Valid Range: 0-65535 (0=off)
	Default Value: 128

	This value, in units of 1.024 microseconds, limits the delay in which a
	receive interrupt is generated. Useful only if RxIntDelay is non-zero,
	this value ensures that an interrupt is generated after the initial
	packet is received within the set amount of time. Proper tuning,
	along with RxIntDelay, may improve traffic throughput in specific network
	conditions.

	Speed
	-----
	(This parameter is supported only on adapters with copper connections.)
	Valid Settings: 0, 10, 100, 1000
	Default Value: 0 (auto-negotiate at all supported speeds)

	Speed forces the line speed to the specified value in megabits per second
	(Mbps). If this parameter is not specified or is set to 0 and the link
	partner is set to auto-negotiate, the board will auto-detect the correct
	speed. Duplex should also be set when Speed is set to either 10 or 100.

	TxDescriptors
	-------------
	Valid Range: 80-256 for 82542 and 82543-based adapters
	80-4096 for all other supported adapters
	Default Value: 256

	This value is the number of transmit descriptors allocated by the driver.
	Increasing this value allows the driver to queue more transmits. Each
	descriptor is 16 bytes.

	NOTE: Depending on the available system resources, the request for a
	higher number of transmit descriptors may be denied. In this case,
	use a lower number.

	TxDescriptorStep
	----------------
	Valid Range: 1 (use every Tx Descriptor)
	4 (use every 4th Tx Descriptor)

	Default Value: 1 (use every Tx Descriptor)

	On certain non-Intel architectures, it has been observed that intense TX
	traffic bursts of short packets may result in an improper descriptor
	writeback. If this occurs, the driver will report a "TX Timeout" and reset
	the adapter, after which the transmit flow will restart, though data may
	have stalled for as much as 10 seconds before it resumes.

	The improper writeback does not occur on the first descriptor in a system
	memory cache-line, which is typically 32 bytes, or 4 descriptors long.

	Setting TxDescriptorStep to a value of 4 will ensure that all TX descriptors
	are aligned to the start of a system memory cache line, and so this problem
	will not occur.

	NOTES: Setting TxDescriptorStep to 4 effectively reduces the number of
	TxDescriptors available for transmits to 1/4 of the normal allocation.
	This has a possible negative performance impact, which may be
	compensated for by allocating more descriptors using the TxDescriptors
	module parameter.

	There are other conditions which may result in "TX Timeout", which will
	not be resolved by the use of the TxDescriptorStep parameter. As the
	issue addressed by this parameter has never been observed on Intel
	Architecture platforms, it should not be used on Intel platforms.

	TxIntDelay
	----------
	Valid Range: 0-65535 (0=off)
	Default Value: 64

	This value delays the generation of transmit interrupts in units of
	1.024 microseconds. Transmit interrupt reduction can improve CPU
	efficiency if properly tuned for specific network traffic. If the
	system is reporting dropped transmits, this value may be set too high
	causing the driver to run out of available transmit descriptors.

	TxAbsIntDelay
	-------------
	(This parameter is supported only on 82540, 82545 and later adapters.)
	Valid Range: 0-65535 (0=off)
	Default Value: 64

	This value, in units of 1.024 microseconds, limits the delay in which a
	transmit interrupt is generated. Useful only if TxIntDelay is non-zero,
	this value ensures that an interrupt is generated after the initial
	packet is sent on the wire within the set amount of time. Proper tuning,
	along with TxIntDelay, may improve traffic throughput in specific
	network conditions.

	XsumRX
	------
	(This parameter is NOT supported on the 82542-based adapter.)
	Valid Range: 0-1
	Default Value: 1

	A value of '1' indicates that the driver should enable IP checksum
	offload for received packets (both UDP and TCP) to the adapter hardware.

	Copybreak
	---------
	Valid Range: 0-xxxxxxx (0=off)
	Default Value: 256
	Usage: insmod e1000.ko copybreak=128

	Driver copies all packets below or equaling this size to a fresh RX
	buffer before handing it up the stack.

	This parameter is different than other parameters, in that it is a
	single (not 1,1,1 etc.) parameter applied to all driver instances and
	it is also available during runtime at
	/sys/module/e1000/parameters/copybreak

	SmartPowerDownEnable
	--------------------
	Valid Range: 0-1
	Default Value: 0 (disabled)

	Allows PHY to turn off in lower power states. The user can turn off
	this parameter in supported chipsets.

	KumeranLockLoss
	---------------
	Valid Range: 0-1
	Default Value: 1 (enabled)

	This workaround skips resetting the PHY at shutdown for the initial
	silicon releases of ICH8 systems.

	Speed and Duplex Configuration
	==============================

	Three keywords are used to control the speed and duplex configuration.
	These keywords are Speed, Duplex, and AutoNeg.

	If the board uses a fiber interface, these keywords are ignored, and the
	fiber interface board only links at 1000 Mbps full-duplex.

	For copper-based boards, the keywords interact as follows:

	The default operation is auto-negotiate. The board advertises all
	supported speed and duplex combinations, and it links at the highest
	common speed and duplex mode IF the link partner is set to auto-negotiate.

	If Speed = 1000, limited auto-negotiation is enabled and only 1000 Mbps
	is advertised (The 1000BaseT spec requires auto-negotiation.)

	If Speed = 10 or 100, then both Speed and Duplex should be set. Auto-
	negotiation is disabled, and the AutoNeg parameter is ignored. Partner
	SHOULD also be forced.

	The AutoNeg parameter is used when more control is required over the
	auto-negotiation process. It should be used when you wish to control which
	speed and duplex combinations are advertised during the auto-negotiation
	process.

	The parameter may be specified as either a decimal or hexadecimal value as
	determined by the bitmap below.

	Bit position 7 6 5 4 3 2 1 0
	Decimal Value 128 64 32 16 8 4 2 1
	Hex value 80 40 20 10 8 4 2 1
	Speed (Mbps) N/A N/A 1000 N/A 100 100 10 10
	Duplex Full Full Half Full Half

	Some examples of using AutoNeg:

	modprobe e1000 AutoNeg=0x01 (Restricts autonegotiation to 10 Half)
	modprobe e1000 AutoNeg=1 (Same as above)
	modprobe e1000 AutoNeg=0x02 (Restricts autonegotiation to 10 Full)
	modprobe e1000 AutoNeg=0x03 (Restricts autonegotiation to 10 Half or 10 Full)
	modprobe e1000 AutoNeg=0x04 (Restricts autonegotiation to 100 Half)
	modprobe e1000 AutoNeg=0x05 (Restricts autonegotiation to 10 Half or 100
	Half)
	modprobe e1000 AutoNeg=0x020 (Restricts autonegotiation to 1000 Full)
	modprobe e1000 AutoNeg=32 (Same as above)

	Note that when this parameter is used, Speed and Duplex must not be specified.

	If the link partner is forced to a specific speed and duplex, then this
	parameter should not be used. Instead, use the Speed and Duplex parameters
	previously mentioned to force the adapter to the same speed and duplex.

	Additional Configurations
	=========================

	Jumbo Frames
	------------
	Jumbo Frames support is enabled by changing the MTU to a value larger than
	the default of 1500. Use the ifconfig command to increase the MTU size.
	For example:

	ifconfig eth<x> mtu 9000 up

	This setting is not saved across reboots. It can be made permanent if
	you add:

	MTU=9000

	to the file /etc/sysconfig/network-scripts/ifcfg-eth<x>. This example
	applies to the Red Hat distributions; other distributions may store this
	setting in a different location.

	Notes:
	Degradation in throughput performance may be observed in some Jumbo frames
	environments. If this is observed, increasing the application's socket buffer
	size and/or increasing the /proc/sys/net/ipv4/tcp_*mem entry values may help.
	See the specific application manual and /usr/src/linux*/Documentation/
	networking/ip-sysctl.txt for more details.

	- The maximum MTU setting for Jumbo Frames is 16110. This value coincides
	with the maximum Jumbo Frames size of 16128.

	- Using Jumbo frames at 10 or 100 Mbps is not supported and may result in
	poor performance or loss of link.

	- Adapters based on the Intel(R) 82542 and 82573V/E controller do not
	support Jumbo Frames. These correspond to the following product names:
	Intel(R) PRO/1000 Gigabit Server Adapter
	Intel(R) PRO/1000 PM Network Connection

	ethtool
	-------
	The driver utilizes the ethtool interface for driver configuration and
	diagnostics, as well as displaying statistical information. The ethtool
	version 1.6 or later is required for this functionality.

	The latest release of ethtool can be found from
	http://ftp.kernel.org/pub/software/network/ethtool/

	Enabling Wake on LAN* (WoL)
	---------------------------
	WoL is configured through the ethtool* utility.

	WoL will be enabled on the system during the next shut down or reboot.
	For this driver version, in order to enable WoL, the e1000 driver must be
	loaded when shutting down or rebooting the system.

	Support
	=======

	For general information, go to the Intel support website at:

	http://support.intel.com

	or the Intel Wired Networking project hosted by Sourceforge at:

	http://sourceforge.net/projects/e1000

	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 e1000-devel@lists.sf.net