Content-addressable memory (CAM) memory technology that searches data
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Comparison: APEX 20KE Virtex-E Devices
Content-addressable memory (CAM) memory technology that searches data content rather than address. When compared RAM, significantly reduces search times because compare input data with list pre-stored entries single clock cycle. therefore accelerates applications that require fast searches databases, lists, patterns, including Ethernet address look-up, data compression, pattern recognition, cache detection, fast routing-table look-up, high-bandwidth address filtering, security firewalls, encryption. Altera® APEX20KE devices only programmable logic devices (PLDs) provide dedicated circuitry. This embedded offers significant performance enhancements more efficient resource utilization than other types CAM. Traditionally, engineers have added discrete their designs, which introduces off-chip, on-chip delays takes valuable board space. Now, using APEX 20KE CAM, engineers take advantage flexibility simple design integration APEX devices, while benefitting from faster access time increased board space offered single-chip solution. APEX 20KE device even accommodate some typical, large-sized Internet applications, such Layer-3 address caching Internet Protocol version (IPv4) switches. APEX 20KE addresses designers' needs offering variety depths widths, configuration flexibility. Altera Applications recently compared APEX 20KE solution with Xilinx emulation test features, performance, area utilization each implementation. This technical brief describes experiment discusses benefits APEX 20KE embedded CAM.
Altera Corporation Innovation Drive Jose, 95134 (408) 544-7000 http://www.altera.com https://websupport.altera.com
Experiment
Altera Applications tested performance Xilinx Virtex-E Altera APEX 20KE devices when implementing largest possible CAM. Although APEX 20KE devices could implement wide 5,120 deep 5,120 Altera Applications restricted testing because largest size XCV1000E device could implement. XCV1000E device largest device readily supported current Xilinx software: Alliance version 2.1i SP2. Altera chose test smallest fastest device from each family that could this size. easily into 8,230 logic element (LE) EP20K200E-1 device. However, Xilinx's implementation required device three times larger, 24,576 equivalent-LE XCV1000E-8 device, used every block available this device.
Setup
implemented both devices with similar function; both implementations used multiple match mode with encoded outputs address width words data width bits. implemented EP20K200E-1 device using MegaWizardPlug-In Manager Quartusversion 1999.10 software; Quartus software then used synthesis place-and-route.
Altera Corporation
M-TB-061-01
Comparison: APEX 20KE Virtex-E Devices
Xilinx provides macro emulate Virtex-E devices. implemented XCV1000E-8 device using Xilinx reference designs. build block, design modified according instructions Xilinx Application Note XAPP (Using Block SelectRAM+ High-Performance Read/Write CAMs). design synthesized with Synopsys FPGA Compiler version software transferred Xilinx Alliance version 2.1i software place-androute.
Area Utilization Results
implement CAM, Xilinx Alliance version 2.1i software required SelectRAM+ Blocks XCV1000E-8 device. same implemented EP20K200E device consumed only embedded system blocks (ESBs) available device. Table shows results experiment, with ESBs SelectRAM+ Blocks converted into bits easy comparison.
Table Area Utilization Comparison
Feature
Bits Used Used Unused Bits Note:
Virtex slice equivalent APEX LEs.
EP20K200E-1
65,536 40,960
XCV1000E-8
393,216 1,732
results show that APEX 20KE devices consume fewer bits than Virtex-E devices have additional memory spare when implementing CAM.
Performance Results
typically implemented high-speed applications. this reason, performance critical design's overall success. Table shows that APEX EP20K200E-1 device operated more than three times frequency Virtex XCV1000E-8 device with same functional implementation.
Table Performance
Feature
Operating Frequency
EP20K200E-1
116.29
XCV1000E-8
45.47
Functionality
implement APEX 20KE embedded with wide range modes options. With Quartus software, designers configure APEX 20KE devices implement single match, multiple match, fast multiple match CAM, with contents encoded unencoded. These modes enable designers optimize area utilization performance. Table describes each mode.
Altera Corporation
Comparison: APEX 20KE Virtex-E Devices
Table Mode Descriptions
Mode Description
Single Match single match mode when input pattern only matches stored pattern. When match found, match flag goes high, output address displays matched addresses. When using this mode, data width cannot exceed bits. This mode provides higher performance than other modes similar implementations. Multiple Match multiple match mode when input pattern matches more than stored pattern. When address found, address match flags corresponding matched outputs high. Encoded addresses generated from match flags using LEs. This mode requires read cycles find matched output. Fast multiple match mode functions same multiple match mode requires only clock cycle find output. fast multiple match mode requires twice number ESBs multiple match mode because uses only half available memory each ESB.
Fast Multiple Match
APEX 20KE devices also have unique ability implement ternary CAM-a configuration that accepts don't care bits-while consuming only limited number additional ESBs. Xilinx Virtex-E devices support ternary CAM. Table compares different implementations supported each device family.
Table Supported Implementations
Implementation
Single Match Mode Multiple Match Mode Fast Multiple Match Mode Ternary
APEX 20KE Embedded
Virtex-E
Sizes
flexibility APEX 20KE devices allows designers implement with variety address depths data widths. example, designers implement APEX 20KE devices wide 5,120 deep 5,120 Virtex-E restricts data width multiples total bits, restricts address depth 128, words. Table compares sizes offered both device families.
Table Size Comparison
Feature
Dimension Widest Dimension Deepest Notes:
Note
APEX 20KE
5,120 5,120
Virtex-E
2,560
Table shows comparison between EP20K1000E XCV1000E-8 devices. Source: Xilinx Application Note XAPP (Using Block SelectRAM+ High-Performance Read/Write CAMs).
Altera Corporation
Comparison: APEX 20KE Virtex-E Devices
Figure shows various applications that APEX 20KE Virtex-E devices address. APEX 20KE devices meet needs small- medium-sized applications many large-sized, high-speed applications. Virtex-E address only small-sized, low-performance applications. implement medium- large-sized applications, designers must create external circuitry around Virtex-E CAM.
Figure Application Sizes
Width
APEX 20KE Virtex
1,024
2,048
4,096 4,096
Depth Small-Sized Applications Switch Address Mapping Packet Header Identification Pattern Recognition Internet Protocol Filter Cache Medium-Sized Applications Address Look-Up Layer Bridges Switches Address Translation Protocol Conversion Gateways Layer Longest Match Address Look-Up IPv4, DECNET Appletalk VPI/VCI Translation ASwitches Large-Sized Applications Cache Network Server Layer Flow Recognition Fair Bandwidth Sharing Layer Address Caching IPv4 SwitchVPI/VCI Translation ASwitches
Conclusion
APEX 20KE embedded provides significant advantages area utilization performance. These advantages combined with ability implement variety sizes modes make APEX 20KE devices ideally suited small-, medium-, several large-sized applications.
Innovation Drive Jose, 95134 (408) 544-7000 http://www.altera.com
Copyright 1999 Altera Corporation. Altera, Quartus, APEX, APEX 20K, APEX 20KE, MegaWizard, EP20K200 trademarks and/or service marks Altera Corporation United States other countries. Other brands products trademarks their respective holders. specifications contained herein subject change without notice. Altera assumes responsibility liability arising application information, product, service described herein except expressly agreed writing Altera Corporation. Altera customers advised obtain latest version device specifications before relying published information before placing orders products services. rights reserved.
Altera Corporation
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