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PEX 8680, PCI Express Gen 2 Switch, 80 Lanes, 20 Ports
Features
PEX 8680 General Features
o 80-lane, 20-port PCIe Gen2 switch - Integrated 5.0 GT/s SerDes o 35 x 35mm2, 1156-ball FCBGA package o Typical Power: 9.0 Watts
The ExpressLaneTM PEX 8680 device offers Multi-Host PCI Express switching capability enabling users to connect multiple hosts to their respective endpoints via scalable, high bandwidth, non-blocking interconnection to a wide variety of applications including servers, storage systems, and communications platforms. The PEX 8680 is well suited for fan-out, aggregation, and peer-to-peer applications.
Multi-Host Architecture The PEX 8680 employs an enhanced version of PLX's field tested PEX 8648 PCIe switch architecture, which allows users to configure the device in legacy single-host mode or multi-host mode with up to six host ports capable of 1+1 (one active & one backup) or N+1 (N active & one backup) host failover. This powerful architectural enhancement enables users to build PCIe based systems to support high-availability, failover, redundant and clustered systems. High Performance & Low Packet Latency The PEX 8680 architecture supports packet cut-thru with a maximum latency of 176ns (x16 to x16). This, combined with large packet memory, flexible common buffer/FC credit pool and non-blocking internal switch architecture, provides full line rate on all ports for performance-hungry applications such as servers and switch fabrics. The low latency enables applications to achieve high throughput and performance. In addition to low latency, the device supports a packet payload size of up to 2048 bytes, enabling the user to achieve even higher throughput. Data Integrity The PEX 8680 provides end-to-end CRC (ECRC) protection and Poison bit support to enable designs that require end-to-end data integrity. PLX also supports data path parity and memory (RAM) error correction circuitry throughout the internal data paths as packets pass through the switch. Flexible Configuration The PEX 8680's 20 ports can be configured to lane widths of x1, x2, x4, x8, or x16. Flexible buffer x4 x8 allocation, along with the device's flexible packet flow control, maximizes PEX 8680 PEX 8680 throughput for applications where more traffic flows in the downstream, rather than 6 x8 6 x4 19 x4 upstream, direction. Any port can be designated as the x16 x8 upstream port, which can be changed dynamically. Figure 1 shows some of the PEX 8680 PEX 8680 PEX 8680's common port configurations in legacy Single-Host mode. 4 x8 10 x4 8 x8
Figure 1. Common Port Configurations
PEX 8680 Key Features
o Standards Compliant - PCI Express Base Specification, r2.0 (backwards compatible w/ PCIe r1.0a/1.1) - PCI Power Management Spec, r1.2 - Microsoft Vista Compliant - Supports Access Control Services - Dynamic link-width control - Dynamic SerDes speed control o High Performance performancePAK Read Pacing (bandwidth throttling) Multicast Dynamic Buffer/FC Credit Pool - Non-blocking switch fabric - Full line rate on all ports - Packet Cut-Thru with 176ns max packet latency (x16 to x16) - 2KB Max Payload Size o Flexible Configuration - Ports configurable as x1, x2, x4, x8, x16 - Registers configurable with strapping pins, EEPROM, I2C, or host software - Lane and polarity reversal - Compatible with PCIe 1.0a PM o Multi-Host & Fail-Over Support - Configurable Non-Transparent (NT) port - Failover with NT port - Up to Six upstream/Host ports with 1+1 or N+1 failover to other upstream ports o Quality of Service (QoS) - Eight traffic classes per port - Weighted round-robin source port arbitration o Reliability, Availability, Serviceability visionPAK Per Port Performance Monitoring Per port payload & header counters SerDes Eye Capture Error Injection and Loopback - 4 Hot Plug Ports with native HP Signals - All ports hot plug capable thru I2C (Hot Plug Controller on every port) - ECRC and Poison bit support - Data Path parity - Memory (RAM) Error Correction - INTA# and FATAL_ERR# signals - Advanced Error Reporting - Port Status bits and GPIO available - Per port error diagnostics - JTAG AC/DC boundary scan
(c) PLX Technology, www.plxtech.com
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PEX 8680, PCI Express Gen 2 Switch, 80 Lanes, 20 Ports
The PEX 8680 can also be configured in Multi-Host mode where users can choose up to six ports as host/upstream ports and assign a desired number of downstream ports to each host. In Multi-Host mode, a virtual switch is created for each host port and its associated downstream ports inside the device. The traffic between the ports of a virtual switch is completely isolated from the traffic in other virtual switches. Figure 2 illustrates some configurations of the PEX 8680 in Multi-Host mode where each ellipse represents a virtual switch inside the device. The PEX 8680 x8 x8 x8 x8 x8 also provides several ways to configure its PEX 8680 PEX 8680 registers. The device can be 2 x8, 4 x4 2 x8, 4x4 4 x4 4 x4 4 x4 configured through 4 x4s 6 x4s strapping pins, I2C interface, host software, or PEX 8680 PEX 8680 an optional serial EEPROM. 16 x4s 12 x4s Figure 2. Common Multi-Host Configurations This allows for easy debug during the development phase, performance monitoring during the operation phase, and driver or software upgrade. Dual-Host & Failover Support In Single-Host mode, the PEX 8680 supports a NonTransparent (NT) Port, which enables the implementation of dual-host systems for redundancy and host failover capability. Primary Host Secondary Host Primary Host Secondary Host The NT port allows systems CPU CPU to isolate host memory domains by presenting the Root Complex processor subsystem as an endpoint rather than NT another memory system. Base PEX 8680 address registers are used Non-Transparent Port to translate addresses; End End End doorbell registers are Point Point Point used to send interrupts between the Figure 3. Non-Transparent Port address domains; and scratchpad registers (accessible by both CPUs) allow inter-processor communication (see Figure 3). Multi-Host & Failover Support In Multi-Host mode, PEX 8680 can be configured with up to six upstream host ports, each with its own dedicated downstream ports. The device can be configured for 1+1 redundancy or N+1 redundancy. The PEX 8680 allows the hosts to communicate their status to each other via special door-bell registers. In failover mode, if a host fails, the host designated for failover will disable the upstream port attached to the failing host and program the downstream ports of that host to its own domain. Figure 4a shows a two host system in MultiHost mode with two virtual switches inside the device and Figure 4b shows Host 1 disabled after failure and Host 2 having taken over all of Host 1's end-points.
Host 1 Host 2 Host 1 Host 2
PEX 8680
PEX 8680
End Point
End Point
End Point
End Point
End Point
End Point
End Point
End Point
Figure 4a. Multi-Host
Figure 4b. Multi-Host Fail-Over
Hot Plug for High Availability Hot plug capability allows users to replace hardware modules and perform maintenance without powering down the system. The PEX 8680 hot plug capability feature makes it suitable for High Availability (HA) applications. Four downstream ports include a Standard Hot Plug Controller. If the PEX 8680 is used in an application where one or more of its downstream ports connect to PCI Express slots, each port's Hot Plug Controller can be used to manage the hot-plug event of its associated slot. Every port on the PEX 8680 is equipped with a hot-plug control/status register to support hot-plug capability through external logic via the I2C interface. SerDes Power and Signal Management The PEX 8680 supports software control of the SerDes outputs to allow optimization of power and signal strength in a system. The PLX SerDes implementation supports four levels of power - off, low, typical, and high. The SerDes block also supports loop-back modes and advanced reporting of error conditions, which enables efficient management of the entire system. Interoperability The PEX 8680 is designed to be fully compliant with the PCI Express Base Specification r2.0, and is backwards compatible to PCI Express Base Specification r1.1 and
(c) PLX Technology, www.plxtech.com
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PEX 8680, PCI Express Gen 2 Switch, 80 Lanes, 20 Ports
r1.0a. Additionally, it supports auto-negotiation, lane reversal, and polarity reversal. Furthermore, the PEX 8680 is tested for Microsoft Vista compliance. All PLX switches undergo thorough interoperability testing in PLX's Interoperability Lab and compliance testing at the PCI-SIG plug-fest.
visionPAKTM
Another PLX exclusive, visionPAK is a debug diagnostics suite of integrated hardware and software instruments that users can use to help bring their systems to market faster. visionPAK features consist of Performance Monitoring, SerDes Eye Capture, Error Injection, SerDes Loopback, and more. Performance Monitoring The PEX 8680's real time performance monitoring allows users to literally "see" ingress and egress performance on each port as traffic passes through the switch using PLX's Software Development Kit (SDK). The monitoring is completely passive and therefore has no affect on overall system performance. Internal counters provide extensive granularity down to traffic & packet type and even allows for the filtering of traffic (i.e. count only Memory Writes). SerDes Eye Capture Users can evaluate their system's signal integrity at the physical layer using the PEX 8680's SerDes Eye Capture feature. Using PLX's SDK, users can view the receiver eye of any lane on the switch. Users can then modify SerDes settings and see the impact on the receiver eye. Figure 5 shows a screenshot of the SerDes Eye Capture feature in the SDK.
performancePAKTM
Exclusive to PLX, performancePAK is a suite of unique and innovative performance features which allows PLX's Gen 2 switches to be the highest performing Gen 2 switches in the market today. The performancePAK features consists of the Read Pacing, Multicast, and Dynamic Buffer Pool. Read Pacing The Read Pacing feature allows users to throttle the amount of read requests being made by downstream devices. When a downstream device requests several long reads back-to-back, the Root Complex gets tied up in serving that downstream port. If that port has a narrow link and is therefore slow in receiving these read packets from the Root Complex, then other downstream ports may become starved - thus, impacting performance. The Read Pacing feature enhances performances by allowing for the adequate servicing of all downstream devices. Multicast The Multicast feature enables the copying of data (packets) from one ingress port to multiple (up to 19) egress ports in one transaction allowing for higher performance in dual-graphics, storage, security, and redundant applications, among others. Multicast relieves the CPU from having to conduct multiple redundant transactions, resulting in higher system performance. Dynamic Buffer Pool The PEX 8680 employs a dynamic buffer pool for Flow Control (FC) management. As opposed to a static buffer scheme which assigns fixed, static buffers to each port, PLX's dynamic buffer allocation scheme utilizes a common pool of FC Credits which are shared by other ports. This shared buffer pool is fully programmable by the user, so FC credits can be allocated among the ports as needed. Not only does this prevent wasted buffers and inappropriate buffer assignments, any unallocated buffers remain in the common buffer pool and can then be used for faster FC credit updates.
Figure 5. SerDes Eye Capture Error Injection & SerDes Loopback Using the PEX 8680's Error Injection feature, users can inject malformed packets and/or fatal errors into their system and evaluate a system's ability to detect and recover from such errors. The PEX 8680 also supports Internal Tx, External Tx, Recovered Clock, and Recovered Data Loopback modes.
(c) PLX Technology, www.plxtech.com
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PEX 8680, PCI Express Gen 2 Switch, 80 Lanes, 20 Ports Applications
Suitable for host-centric as well as peer-to-peer traffic patterns, the PEX 8680 can be configured for a wide variety of form factors and applications. Host Centric Fan-out The PEX 8680, with its symmetric or asymmetric lane configuration capability, allows user-specific tuning to a variety of host-centric applications. Figure 6 shows a server design where, in a quad or multi processor system, users can assign endpoints/slots to CPU cores to distribute the system load. The packets directed to different CPUs will go to different (user assigned) PEX 8680 upstream ports, allowing better queuing and load balancing capability for higher performance.
CPU CPU CPU CPU
Embedded or Communications Systems The PEX 8680's 80 lanes can come in handy for embedded or communications applications requiring heavy processing and/or connectivity to multiple endpoints. Figure 8a shows an embedded system where the PEX 8680 is being used to fan-out to eight endpoints using x8 and x16 links. Figure 8b shows a communications system where the PEX 8680 is using x16 and x8 links to fan out to I/Os and three CPUs which have been configured as endpoints. These CPUs will run as endpoints, conducting different processing tasks while the host CPU (connected to the PEX 8680 via a x16 upstream link) manages them.
CPU CPU
Chip Set
Memory
Chip Set
Chipset
Endpoint
x16
x16
x4 x16
x8
x8
PEX 8680
x8s x16s & x8s
PEX 8680
x16s
PEX 8680
Endpoint
I/O I/O
x8s
x4s
I/O I/O
I/O I/O
I/O
CPU Endpoint CPU Endpoint
I/O
CPU Endpoint
PCIe Gen1 or PCIe Gen2 slots
Figure 8a. Embedded System
Figure 8b. Comms System
Figure 6. Host Centric Dual Upstream Multi-Host Systems In multi-host mode, the PEX 8680 can support up to six hosts at once. By creating six virtual switches, the PEX 8680 allows six hosts to fan-out to their respective endpoints. This reduces the number of switches required for fan-out, saving precious board space and power. In Figure 7, the PEX 8680 is being shared by six different CPU cores (hosts) on three servers, with each CPU core running its own applications (I/Os). The PEX 8680 assigns the endpoints to the appropriate host and isolates them from the other hosts. In Figure 7, the endpoints are assigned to the CPU core of the same color.
CPU CPU CPU CPU CPU CPU
N+1 Fail-Over in Storage Systems The PEX 8680's Multi-Host feature can also be used to develop storage array clusters where each host manages a set of storage devices independent of others (Figure 9). Users can designate one of the hosts as the failover-host for all the other hosts while actively managing its own endpoints. The failover-host will communicate with other hosts for status/heartbeat information and execute a failover event if/when it gets triggered.
CPU CPU CPU CPU CPU CPU CPU CPU
x4
x4
x8
x8
PEX 8680
x4 x4 x8 x8
Chip Set
Chip Set
Chip Set
PEX 8680
I/O I/O I/O I/O I/O I/O I/O I/O I/O
PEX PEX 8616 8616 PEX 8612 x4 x4 x4 x4 PEX 8612 x4 x4 FC FC x4 x4 FC FC
FC FC FC FC
8 Disk Chassis 8 Disk Chassis 8 Disk Chassis 8 Disk Chassis
Figure 7. Multi-Host System
Figure 9. N+1 Failover
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(c) PLX Technology, www.plxtech.com
PEX 8680, PCI Express Gen 2 Switch, 80 Lanes, 20 Ports Software Usage Model
From a system model viewpoint, each PCI Express port is a virtual PCI to PCI bridge device and has its own set of PCI Express configuration registers. It is through the upstream port that the BIOS or host can configure the other ports using standard PCI enumeration. The virtual PCI to PCI bridges within the PEX 8680 are compliant to the PCI and PCI Express system models. The Configuration Space Registers (CSRs) in a virtual primary/secondary PCI to PCI bridge are accessible by type 0 configuration cycles through the virtual primary bus interface (matching bus number, device number, and function number). Interrupt Sources/Events The PEX 8680 switch supports the INTx interrupt message type (compatible with PCI 2.3 Interrupt signals) or Message Signaled Interrupts (MSI) when enabled. Interrupts/messages are generated by PEX 8680 for hot plug events, doorbell interrupts, baseline error reporting, and advanced error reporting. ExpressLane PEX 8680 RDK The PEX 8680 RDK (see Figure 10) is a hardware module containing the PEX 8680 which plugs right into your system. The PEX 8680 RDK can be used to test and validate customer software, or used as an evaluation vehicle for PEX 8680 features and benefits. The PEX 8680 RDK provides everything that a user needs to get their hardware and software development started. Software Development Kit (SDK) PLX's Software Development Kit is available for download at www.plxtech.com/sdk. The software development kit includes drivers, source code, and GUI interfaces to aid in configuring and debugging the PEX 8680. For more information, please refer to the PEX 8680 RDK Product Brief. Both performancePAK and visionPAK are supported by PLX's RDK and SDK, the industry's most advanced hardware- and software-development kits.
Product Ordering Information
Part Number
PEX8680-AA50BC F PEX8680-16U8D BB RDK
Description
80-Lane, 20-Port PCI Express Switch, Pb-Free (35x35mm2) PEX 8680 Rapid Development Kit with x16 Upstream and Eight x8 Downstream
Figure 10. PEX8680-16U8D BB RDK
PLX Technology, Inc. All rights reserved. PLX, the PLX logo, ExpressLane, Read Pacing and Dual Cast are trademarks of PLX Technology, Inc. All other product names that appear in this material are for identification purposes only and are acknowledged to be trademarks or registered trademarks of their respective companies. Information supplied by PLX is believed to be accurate and reliable, but PLX assumes no responsibility for any errors that may appear in this material. PLX reserves the right, without notice, to make changes in product design or specification.
Development Tools
PLX offers hardware and software tools to enable rapid customer design activity. These tools consist of a hardware module (PEX 8680 RDK), hardware documentation (available at www.plxtech.com), and a Software Development Kit (also available at www.plxtech.com).
Visit www.plxtech.com for more information.
(c) PLX Technology, www.plxtech.com
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