National Instruments MXI-Express Gen-3 x16 User manual

USER MANUAL
MXI-Express Gen-3 x16
MXI-Express Gen-3 x16 Multisystem eXtension Interface for PCI
Express, CompactPCI Express, and PXI Express Bus Systems
This document provides installation, configuration, and reference information for MXI-
Express Gen-3 x16 controllers.
Caution This icon denotes a caution, which advises you of precautions to take to
avoid injury, loss of data, or a system crash.
Caution Using the MXI-Express Gen-3 x16 controllers in a manner not described
in this document may impair the protection the controllers provide.
Contents
Overview...................................................................................................................................2
Description and Features...........................................................................................................3
Functional Block Diagram........................................................................................................ 4
Basic MXI-Express Gen-3 x16 Systems...................................................................................6
Larger MXI-Express Gen-3 x16 Systems.................................................................................7
Connection Options...................................................................................................................8
Compatibility with Host PCs.................................................................................................. 10
Installation and Configuration.................................................................................................11
Equipment Needed.......................................................................................................... 11
Unpacking............................................................................................................................... 11
Hardware Installation..............................................................................................................12
Installing a PCIe-8398.................................................................................................... 12
Installing the Low-Profile Bracket on the PCIe-8398 (Optional)...................................13
Installing a PXIe-8398, PXIe-8399, or PXIe-8394.........................................................14
Cabling............................................................................................................................ 16
Powering On the MXI-Express Gen-3 x16 System........................................................ 17
Powering Off the MXI-Express Gen-3 x16 System....................................................... 17
LED Indicators........................................................................................................................18
PXI Express Onboard LEDs........................................................................................... 19
PCIe-8398 Onboard LEDs.............................................................................................. 21
Software Installation and Configuration................................................................................. 22

Specifications.......................................................................................................................... 23
PCIe-8398 (156877x-01L) Specifications...................................................................... 23
PXIe-8398 (156874x-01L) Specifications...................................................................... 26
PXIe-8399 (156874x-02L) Specifications...................................................................... 29
PXIe-8394 (156874x-04L) Specifications...................................................................... 32
Common Questions.................................................................................................................35
General Hardware........................................................................................................... 35
MXI-Express Gen-3 x16 Upgrade Questions................................................................. 36
General Software.............................................................................................................36
Documentation Notice for Third Party Software....................................................................37
Overview
Gen-3 MXI-Express is based on off-the-shelf PCI Express technologies. A Gen-3 MXI-
Express module can control PXI Express or CompactPCI Express chassis from a PC or a PXI
Express or CompactPCI Express chassis. The architecture is transparent to device drivers, so
no additional software is needed for PXI Express devices installed in connected chassis.
Note For full PXI/PXI Express functionality such as chassis and controller
identification, trigger routing, and slot detection, install the PXI Platform Services
software included with your kit. You also can find this software at ni.com/
updates by searching for PXI Platform Services.
The basic PCI Express lane consists of dual unidirectional differential links implemented as
one transmit pair and one receive pair. The link between the PC and chassis can be up to 16
lanes wide and supports speeds up to PCI Express Gen-3.
The following table lists the signaling rate of each PCI Express generation.
Table 1. PXI Express Generation Signaling Rates
PCI Express Generation Signaling Rate
First 2.5 Gb/s/lane/direction of raw bandwidth
Second 5.0 Gb/s/lane/direction of raw bandwidth
Third 8.0 Gb/s/lane/direction of raw bandwidth
Note This link is compatible with the cabled PCI Express specification developed
by the PCI-SIG.
2| ni.com | MXI-Express Gen-3 x16 User Manual

Description and Features
MXI-Express Gen-3 x16 extends PCI Express communication over a cable up to 3 m. With
MXI-Express Gen-3 x16, you can do the following:
• Control a PXI Express or CompactPCI Express backplane with a PCI Express-based PC.
• Physically separate the measurement or automation system from a host PC.
• Control multiple PXI Express or CompactPCI Express chassis with a single PCI Express-
based PC or PXI Express embedded controller. (The PXIe-8398 and PXIe-8399
controllers also can control multiple chassis in a daisy-chain configuration.)
The following table lists the models and their features for comparison.
Table 2. Feature Comparison of Available MXI-Express Gen-3 x16 Interfaces
Model Slot Type Number of Lanes Cable Support
PCIe-8398 PCI Express Gen-3 x16 16 MXI-Express x8
PXIe-8394 PXI Express Peripheral
Expansion Module
16 MXI-Express x8,
MXI-Express x4
PXIe-8398 PXI Express Controller 16 MXI-Express x8,
MXI-Express x4
PXIe-8399 PXI Express Controller
With One Expansion Slot
32 MXI-Express x8,
MXI-Express x4
Tip For optimum link widths and performance, use the PXIe-8394, PXIe-8398, and
PXIe-8399 in chassis that support Gen 3 links.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 3

Functional Block Diagram
Figure 1. PCIe-8398 (156877x-01L) Block Diagram
MXI-Express
Gen-3 x16
PWR/LNK
Status LED
PCI Express Gen-3 x16
PCI Express Gen-3 x16
PCI Express
Switch
4| ni.com | MXI-Express Gen-3 x16 User Manual

Figure 2. PXIe-8398 (156874x-01L) and PXIe-8399 (156874x-02L) Block Diagram
MXI-Express
Gen-3 x16
PCI Express Gen-3 x16
PCI Express Gen-3 x4
PCI Express Gen-3 x4
PCI Express Gen-3 x4
PCI Express Gen-3 x4
PCI Express
to
PCI Bridge
SMBus
Master
PCI Express
Switch
Note The width and speed of the PXI Express backplane links are chassis
dependent.
The PXIe-8398 and PXIe-8399 work in both two and four-link chassis. A four-link chassis
supports four links up to x4 width each, for a maximum of 16 PCI Express lanes. A two-link
chassis supports one link up to x8 and a second link up to x16, for a maximum of 24 PCI
Express lanes. The PXIe-8398 and PXIe-8399 maximize the use of all available backplane
lanes for either configuration.
Note National Instruments offers Gen 3 PXI Express chassis that allow the
PXIe-8398 and PXIe-8399 to establish Gen 3 backplane links.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 5

Figure 3. PXIe-8394 (156874x-04L) Block Diagram
PCI Express
Switch
PCI Express Gen-3 x16
PCI Express Gen-3 x8
MXI-Express
Gen-3 x16
Note The width and speed of the PXIe-8394 backplane links are chassis
dependent.
Note National Instruments offers Gen 3 PXI Express chassis that allow the
PXIe-8394 to establish Gen 3 backplane links. A chassis can support up to a x8 link.
Basic MXI-Express Gen-3 x16 Systems
The simplest MXI-Express Gen-3 x16 system consists of a PCIe-8398 in a PC connected to a
PXIe-8398 in the controller slot of a PXI Express chassis, as shown in the following figure.
Figure 4. Example of a Basic MXI-Express Gen-3 x16 Link Topology
Note In this manual, whenever a PXI Express chassis is referenced, you could use
a CompactPCI Express chassis instead.
6| ni.com | MXI-Express Gen-3 x16 User Manual

Larger MXI-Express Gen-3 x16 Systems
There are several ways to connect multiple chassis to a host system. Which you choose
depends on your design goals and requirements.
If you are using a PC to control the chassis, and if multiple x16 PCI Express slots are available
in the host PC, you can use multiple PCIe-8398 modules to connect to the PXIe-8398 in each
chassis ("star" topology). This method offers the most bandwidth and lowest latency to the
host for all the chassis.
Figure 5. Example of a Star MXI-Express Gen-3 x16 System Expansion Topology
If you are using a PC to control multiple chassis but do not have additional PCI Express slots
in the PC, you can use a PXIe-8399 to daisy-chain to an additional chassis ("daisy-chain"
topology). The PXIe-8399 supports two x16 links on its front panel, and you can connect the
second link to an additional chassis. For example, you could set up two chassis using a
PCIe-8398 in the host PC cabled to a PXIe-8399 in the first chassis. The PXIe-8399 in the first
chassis would also be cabled to a PXIe-8398 in the second chassis. If a third chassis is desired,
the second chassis could use another PXIe-8399.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 7

Figure 6. Example of a Daisy-Chain MXI-Express Gen-3 x16 System Expansion
Topology
If you are using an embedded controller, you can use a PXIe-8394 to expand to additional
chassis. As with a PC host, you can use a PXIe-8394 card per additional chassis (preferred), or
you can daisy-chain additional chassis using the PXIe-8399. The PXIe-8394 backplane
connection is limited to Gen 3 x8.
Figure 7. Example of a MXI-Express Gen-3 x16 System Expansion Topology Using a
PXIe-8394 in Each Chassis
Systems need not be exclusively star or daisy-chain. It is generally preferable to use a star
topology, but you can daisy-chain or star additional chassis as needed. There are additional
choices, described in the next section, if the full x16 bandwidth is not required.
Connection Options
The MXI-Express Gen-3 x16 connectors are modular and can be cabled in several
configurations. The hardware makes the configurations without user intervention. The
8| ni.com | MXI-Express Gen-3 x16 User Manual

configuration mechanism requires PCI Express cables, not the connector-compatible cables
that other standards use. When multiple cables are used for a single link, the cables must be
the same length.
Note National Instruments offers x8 cables. x16 connections require two cables,
and the cables must connect the ports in ascending order. For example, ports 1-2 of a
PCIe-8398 will connect to ports 1-2 of a PXIe-8398, and ports 3-4 will connect to
3-4.
For the PXIe-8399, connect daisy-chain ports 5 and 6 to ports 1 and 2 on the PXIe-8398 or
PXIe-8399.
Figure 8. Connection Options
PXIe-8399 PXIe-8398 PXIe-8394
PCIe-8398
PXIe-8399 PXIe-8398 PXIe-8394
PWR/
LINK
PWR/
LINK
PWR/
LINK
PWR/
LINK
4
1
4
3
2
1
4
3
2
1
4
3
2
1
8
7
6
5
PWR/
LINK
MXI-Express MXI-Express MXI-Express
Port 1 of the PXIe-8398 and PXIe-8399 is upstream facing, meaning it is the link going toward
the host. This means it is connected to a PXIe-8394, PCIe-8398, or a downstream facing port
of a PXIe-8398 or PXIe-8399.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 9

Ports 1-4 ordinarily are cabled to the host PC or the chassis containing the embedded
controller. In this configuration, ports 1-4 form a x16 link, offering the highest throughput.
Ports 5-8 of a PXIe-8399 and ports 1-4 of a PXIe-8394 and PCIe-8398 are always downstream
facing, meaning they may be connected only to additional chassis that are farther from the
host. They ordinarily are connected to a single PXIe-8398 or PXIe-8399.
Ports 2, 3, and 4 of the PXIe-8398 and PXIe-8399 are upstream facing by default, but they
change direction based on cabling. While they are normally used (along with port 1) to form a
x16 upstream link, they may alternatively be connected to additional chassis, and they become
downstream facing ports. There can be only one upstream facing link per chassis, but it may
comprise one, two, or four ports to form a x4, x8, or x16 link.
The following table lists possible configurations.
Module Configuration 1 Configuration 2 Configuration 3 Configuration 4
PCIe-8398 1-4: x16 1-2: x8
3-4: x8
— —
PXIe-8394,
PXIe-8398,
PXIe-8399
ports 1-4
1-4: x16 1-2: x8
3-4: x8
1-2: x8
3: x4
4: x4
1: x4
2: x4
3: x4
4: x4
PXIe-8399
ports 5-8
5-8: x16 5-6: x8
7-8: x8
5-6: x8
7: x4
8: x4
5: x4
6: x4
7: x4
8: x4
The flexible port configurations allow you to prioritize bandwidth (Configuration 1), high
fanout (Configuration 4), or a blend of the two.
Compatibility with Host PCs
The BIOS of some host computers may have limited support or no support for extending the
PCI Express fabric. These systems may fail to boot or fail to function correctly.
For more information about host system compatibility with MXI-Express Gen-3 x16 products,
refer to the NI Developer Zone document Tips to Help You Successfully Use NI MXI-Express
Controllers at ni.com.
10 | ni.com | MXI-Express Gen-3 x16 User Manual

Installation and Configuration
This section explains how to unpack, install, and configure the MXI-Express Gen-3 x16
hardware and software.
Equipment Needed
Connecting a PC to an Expansion Chassis
• Host PC with an available PCI Express Gen-3 x16 slot
• PXI Express chassis
• Two Gen 3 MXI-Express x8 cables
• One PCIe-8398
• One PXIe-8398
Connecting Additional Expansion Chassis to a System with a
PXIe-8399
• Chassis to daisy-chain from with a PXIe-8399 in slot 1
• Expansion chassis to daisy-chain to
• Two Gen 3 MXI-Express x8 cables
• One PXIe-8398
Connecting Additional Expansion Chassis to a System with a
PXIe-8394
• Chassis to daisy-chain from
• Expansion chassis to daisy-chain to
• One Gen 3 MXI-Express x8 cable
• One PXIe-8398 or PXIe-8399
• One PCIe-8394
Note Not all PCI Express expansion slots that have x16 physical connectors are
electrically capable of x16 PCI Express operation. Check with the motherboard
manufacturer to verify that the slot is capable of x16 PCI Express operation.
Unpacking
Your MXI-Express Gen-3 x16 products are shipped in antistatic packages to prevent
electrostatic discharge (ESD) to the devices. ESD can damage several components on the
device.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 11

Caution Never touch the exposed pins of connectors. Doing so may damage the
device.
To avoid such damage in handling the device, take the following precautions:
• Ground yourself using a grounding strap or by holding a grounded object.
• Touch the antistatic package to a metal part of the computer chassis before removing the
device from the package.
Remove the device from the package and inspect the device for loose components or any sign
of damage. Notify NI if the device appears damaged in any way. Do not install a damaged
device into the computer or into a PXI Express or CompactPCI Express chassis.
Store the device in the antistatic envelope when not in use.
Hardware Installation
The following are general instructions for installing the MXI-Express Gen-3 x16 products.
Consult your computer user manual or technical reference manual for further instructions and
warnings.
Caution The protection provided by the MXI-Express Gen-3 x16 products can be
impaired if they are used in a manner not described in this document.
Installing a PCIe-8398
Complete the following steps to install the PCIe-8398 in your computer.
1. Power off your computer.
Caution To protect both yourself and the computer from electrical hazards,
your computer should remain off until you finish installing all hardware as
instructed.
2. Remove the top cover or access port to the PCI Express expansion slots.
3. Touch the metal part of the power supply case inside the computer to discharge any static
electricity that might be on your clothes or body.
4. Unplug the computer and wait 30 seconds to allow the energy stored in the computer’s
power supply to fully dissipate.
5. Select any available PCI Express expansion slot (Gen-3 x16).
6. Locate the metal bracket that covers the cut-out in the back panel of the computer for the
slot you have selected. Remove and save the bracket-retaining screw and the bracket
cover.
7. Line up the PCIe-8398 with the slot on the back panel. Slowly lower the PCIe-8398 until
its card-edge connector is resting on the expansion slot receptacle. Using slow, evenly
distributed pressure, press the PCIe-8398 straight down until it seats in the expansion slot,
as shown in the following figure.
8. Secure the PCIe-8398 to the back panel rail using a bracket retaining screw.
12 | ni.com | MXI-Express Gen-3 x16 User Manual

9. Replace the computer cover.
10. Plug in the computer.
Figure 9. Installing the PCIe-8398
123
1. PCIe-8398
2. PCI Express x16 Card-Edge Connector
3. PCI Express Slot (x16)
Installing the Low-Profile Bracket on the PCIe-8398
(Optional)
To install the PCIe-8398 in a host computer that requires a low-profile height card, you must
replace the front bracket with the low-profile bracket included with your kit. Complete the
following steps to replace the bracket.
1. Remove the standard height front bracket already installed on your PCIe-8398 card by
removing the two 4-40 × 5/32 in. Phillips head screws that attach the bracket to the card.
Note that the two mounting tabs for the standard height bracket rest against the back side
of the card. Set the two screws aside to re-use when installing the low-profile bracket.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 13

Figure 10. Removing the Standard Bracket from the PCIe-8398
3
5
4
6
1
2
1. 4-40 × 5/32 in. Phillips Head Screw (x2)
2. Top Side of Card
3. LED
4. Bracket Hole for LED
5. Bracket Hole for Connector
6. Bracket
2. Fit the low-profile bracket onto the PCIe-8398. Note that the two mounting tabs that the
screws thread into rest against the back side of the card for the low-profile bracket.
Ensure that the LED is situated in the display hole correctly.
3. Align the mounting holes on the card with the threaded holes on the mounting tabs of the
bracket, and insert the screws from the top side.
4. Tighten each screw to a maximum torque of 5 in. • lb (0.565 N • m).
Installing a PXIe-8398, PXIe-8399, or PXIe-8394
The following table provides information on which PXI Express MXI-Express Gen-3 x16
boards are compatible with which chassis slot types.
14 | ni.com | MXI-Express Gen-3 x16 User Manual

Table 3. MXI-Express Gen-3 x16 PXI Express Board Slot Type Compatibility
PXI Express Board PXI Express Chassis
Controller Peripheral Hybrid
PXIe-8398 ✓— —
PXIe-8399 ✓— —
PXIe-8394 — ✓ ✓
Note In this section, all the above models are referred to as a PXI Express board.
Complete the following steps to install the PXI Express board in your PXI Express or
CompactPCI Express chassis.
1. Power off your PXI Express or CompactPCI Express chassis, but leave it plugged in
while installing the PXI Express board. The power cord grounds the chassis and protects
it from electrical damage while you install the module.
Caution To protect both yourself and the chassis from electrical hazards,
leave the chassis off until you finish installing the PXI Express board.
2. Remove or open any doors or covers blocking access to the slot in which you intend to
install the PXI Express board.
3. Touch a metal part of the chassis to discharge any static electricity that might be on your
clothes or body.
4. Make sure the injector/ejector handle is in its downward position. Be sure to remove all
connector packaging and protective caps from retaining screws on the module. Align the
PXI Express board with the card guides on the top and bottom of the system controller
slot.
Caution Do not raise the injector/ejector handle as you insert the PXI Express
board. It will not insert properly unless the handle is in its downward position
so that it does not interfere with the injector/ejector rail on the chassis, as
shown in the following figure.
5. Hold the handle as you slowly slide the module into the chassis until the handle catches
on the injector/ejector rail.
6. Raise the injector/ejector handle until the module firmly seats into the backplane
receptacle connectors. The front panel of the PXI Express board should be even with the
front panel of the chassis.
Note LEDs on the back side of the PXIe-8398 or PXIe-8399 will light,
indicating the presence of 5 V auxiliary power. Refer to the LED Indicators
section for details.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 15

7. Tighten the bracket-retaining screws on the top and bottom of the front panel to secure
the PXI Express board to the chassis.
8. Replace or close any doors or covers to the chassis.
The following figure shows a PXI Express board just before installation in the system
controller slot of a PXI Express chassis.
Figure 11. Example PXI Express Board Installation In a PXI Express Chassis
3
1
4
2
1. PXI Express/CompactPCI Express Chassis
2. PXI Express Board
3. Ejector Handle in Down Position
4. Injector/Ejector Rail
Cabling
The following table shows the various MXI-Express x8 copper cables available from National
Instruments.
Table 4. National Instruments MXI-Express x8 Copper Cables
Cable Length (Meters) Description Part Number
1 m MXI-Express x8 copper 785550-01
3 m MXI-Express x8 785550-03
16 | ni.com | MXI-Express Gen-3 x16 User Manual

Connect the MXI-Express x8 cables to both MXI-Express Gen-3 x16 modules. The cables
have no polarity, so either end may be connected to either card.
Note Two x8 cables plugged into the MXI-Express Gen-3 x16 modules make the
x16 link.
Caution Do not remove the cable after the system is powered on. Doing so can
hang or cause errors in applications communicating with devices behind MXI-
Express Gen-3 x16. If a cable becomes unplugged, plug it back into the system. You
will need to restart your computer.
Powering On the MXI-Express Gen-3 x16 System
1. Power on all the expansion chassis in any order you choose.
The PXIe-8398 has a built-in feature that powers on/off the chassis it is controlling when
the host system is powered on/off. You can override this feature by manually powering on
the downstream chassis through chassis-specific means.
2. Power on the host.
Note There are no requirements for how expansion chassis are powered up relative
to each other, as long as they are all on before the computer is powered on.
Observe the LED status on the PCIe-8398, PXIe-8399, PXIe-8398, and PXIe-8394 where
applicable. A properly connected and powered up system should report a valid link and power
status on all of these boards once the host PC is powered on. Refer to the LED Indicators
section for more information.
Typical PCI Express switches are used to add PCI devices to a PCI hierarchy in which all the
bridges and devices are contained within a single chassis. Because of this, BIOSes and
operating systems make the assumption that all PCI devices in the entire hierarchy will be
available as soon as code execution begins at power-up time. This assumption means that all
of the expansion chassis must be powered on before the host PC for the BIOS and OS to
correctly configure a MXI-Express Gen-3 x16 system.
Powering Off the MXI-Express Gen-3 x16 System
Once the host PC is powered off, the expansion chassis will power down automatically.
Because operating systems and drivers commonly make the assumption that PCI devices will
be present in the system from power-up to power-down, it is important to not power off the
expansion chassis until after the host PC is powered off. Powering off the expansion chassis
while the host is still on can cause crashes or hangs.
Note To power off the chassis while the host computer or host chassis is on, you
may need to hold the power button for at least four seconds.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 17

LED Indicators
The LEDs on MXI-Express Gen-3 x16 cards display status information about power supplies
and link state. The PCIe-8398, PXIe-8398, and PXIe-8394 have one tri-color LED on the
panel, indicating power and link status. The PXIe-8399 has two tri-color LEDs.
Board LED Color Meaning
PXIe-8398 (156874x-01L)
PXIe-8394 (156874x-04L)
PXIe-8399 (156874x-02L)
PWR/LINK Off Power is off
Blinking Red Power is out of spec
Solid Amber Power is within spec; no cable link,
or not all cables linked
Solid Green Power is within spec; link
established on all connected cables
Board LED Color Meaning
PCIe-8398 (156877x-01L) PWR/LINK Solid Red Thermal limit has been
exceeded1
Off Power is off
Blinking Red Power is out of spec
Solid Amber Power is within spec; no cable
link, or not all cables linked
Solid Green Power is within spec; links
established on all connected
cables
1 To clear this state, remove all power from the board. Ensure the heatsink is dust free and
check for air blockages in the chassis.
Pay special attention to the solid red state of the PCIe-8398 front panel LED. In the event of a
fan failure, a thermal limit in the PCI Express switch could be exceeded. To protect the board,
the internal temperature of the PCI Express switch is monitored. If the temperature exceeds a
predetermined limit, the board shuts down, and the front panel LED is solid red.
To clear the solid red state, remove all power from the board. Ensure the heatsink is dust free,
check the fan to verify it is operating, and check the computer to ensure there are no airflow
blockages.
18 | ni.com | MXI-Express Gen-3 x16 User Manual

PXI Express Onboard LEDs
The PXIe-8394, PXIe-8398, and PXIe-8399 have additional LEDs that provide information
about the status of several PCI Express links.
Each LED is an indicator for four PCI Express lanes. Blink patterns are encoded into each
LED to indicate the number of lanes linked and the link speed. The blink pattern repeats every
two seconds. In general, if the LED is on, it means all four lanes are linked, and the number of
blinks indicates the speed. If the LED is off but blinking on, it means fewer than four lanes are
linked, and the number of blinks indicates the speed. The following table lists the patterns.
LED Blink Pattern (Two-Second Period) Meaning
Off No link
On All four lanes linked at PCI Express Gen 3
Primarily on, blinks off twice All four lanes linked at PCI Express Gen 2
Primarily on, blinks off once All four lanes linked at PCI Express Gen 1
Primarily off, blinks on three times One or two lanes linked at PCI Express Gen 3
Primarily off, blinks on twice One or two lanes linked at PCI Express Gen 2
Primarily off, blinks on once One or two lanes linked at PCI Express Gen 1
Note The following table lists the maximum theoretical throughput of PCI Express
lanes. Raw Bitrate is the speed of bits on the wire. Bitrate After Encoding is the
speed of bits after subtracting symbol encoding overhead, and is the max theoretical
throughput. You'll typically get 70% to 80% of the after-encoding rate after protocol
overhead and other detractors.
PCI Express Generation Raw Bitrate Bitrate After Encoding
PCI Express Gen 3 8 Gb/s/lane 7.88 Gb/s/lane
PCI Express Gen 2 5 Gb/s/lane 4 Gb/s/lane
PCI Express Gen 1 2.5 Gb/s/lane 2 Gb/s/lane
LEDs for Ports 1-4
Onboard link indicators for front panel cable links 1-4 are directly behind the connectors on
the back side of the board, as shown in the following figure. The LEDs represent the lanes of
the port they're adjacent to.
MXI-Express Gen-3 x16 User Manual | © National Instruments | 19

Figure 12. LEDs for Ports 1-4
LEDs for Ports 5-8 of the PXIe-8399
These LEDs, shown in the following figure, are between the two PCBs that comprise the
PXIe-8399. They are on the smaller PCB and may be visible through openings on the top of
the chassis. They represent, from top-right to bottom-left, ports 5, 6, 7, and 8.
Figure 13. PXIe-8399 LEDs for Ports 5-8
5
6
7
8
LEDs for Backplane Links
Onboard link indicators for the first 16 backplane lanes are on the top side of the board, as
shown in the following figure.
20 | ni.com | MXI-Express Gen-3 x16 User Manual