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Home > Technology Center > External Memory > QDR I / QDR II Print This Page Subscribe to Email Memory Solutions Center: QDRII SRAM QDRII SRAM devices enable you to maximize memory bandwidth with separate read and write ports. The QDRII architecture features two data ports operating twice per clock cycle to deliver a total of four data instructions per cycle. The resulting performance increase is particularly valuable in bandwidth-intensive applications such as main memory for look-up tables (LUTs), linked lists, and controller buffer memory. QDRII and QDRII+ devices offer significant benefits over QDR devices, including higher performance, increased data valid time, simplified data capture, a guaranteed relationship between clock rate and data rate, and an overall ease-of-design. The QDR SRAM website contains more information on the benefits of QDRII devices. Table 1 lists QDRII/QDRII+ SRAM memory interface performance support in Altera® FPGAs. Table 1. QDRII/QDRII+ SRAM Memory Interface Performance Support in Altera FPGAs Device Maximum QDRII/QDRII+ SRAM Interface Performance Stratix® III 1.4 Gbps (1) (350 MHz) Stratix II 1 Gbps (1) (250 MHz) Stratix II GX 1 Gbps (1) (250 MHz) HardCopy® II 1 Gbps (1) (250 MHz) Stratix 800 Mbps (200 MHz) Stratix GX 800 Mbps (200 MHz) Cyclone® III 667 Mbps (167 MHz) Cyclone II 667 Mbps (167 MHz) Note:  For both read and write ports Technical Documentation Altera offers the following technical documentation that contains information on device support for the QDR and QDRII memory interfaces, as shown in Table 2. Table 2. QDRII SRAM Technical Documentation Device Handbooks Applicable Devices Stratix III Device Handbook: External Memory Interfaces in Stratix III Devices (PDF) chapter Stratix III Stratix II Device Handbook: External Memory Device Interfaces (PDF) chapter Using Selectable I/O Standards (PDF) chapter Stratix II Stratix/Stratix GX Device Handbook: External Memory Device Interfaces (PDF) chapter Using Selectable I/O Standards (PDF) chapter Stratix / Stratix GX Cyclone III Device Handbook: External Memory Interfaces in Cyclone III Devices (PDF) chapter Cyclone III Cyclone II Device Handbook: External Memory Device Interfaces (PDF) chapter Using Selectable I/O Standards (PDF) chapter Cyclone II White Papers Applicable Devices Selecting the Right High-Speed Memory Technology for Your System (PDF) All User Guides Applicable Devices QDRII SRAM Controller MegaCore Function User Guide (PDF)  HardCopy II Stratix/Stratix GX Stratix II/Stratix II GX Application Notes Applicable Devices AN 326: Interfacing QDRII SRAM With Stratix II Devices (PDF) Stratix II AN 349: QDR SRAM Controller Reference Design for Stratix & Stratix GX Devices (PDF) Stratix Stratix GX Hardware Test Results Applicable Devices Hardware Test Results Stratix Software Support and Tools Altera offers the tools shown in Table 3 to aid in the QDRII and QDRII+ SRAM memory interface design process. Table 3. QDRII SRAM Software and Support Tools Feature Applicable Devices TimeQuest Timing Analyzer All IBIS Models for I/O Buffers Stratix, Stratix GX, Stratix II, Stratix II GX IP Cores and Reference Designs Table 4 lists QDRII SRAM controller intellectual property (IP) cores and reference designs available from Altera. Table 4. QDRII SRAM  IP Cores and Reference Designs Controller Name Free Evaluation Vendor Devices Supported QDRII SRAM Controller MegaCore® Function  Yes Altera Stratix III, Stratix II, Stratix II GX, Stratix, Stratix GX Development Kits and Hardware Reference Platforms Table 5 lists memory hardware reference platforms available from Altera. The Gerber files, layout, termination recommendations, and signal integrity analysis information of these reference platforms are also available. Table 5. QDRII SRAM Development Kits and Hardware Reference Platforms Board Name Vendor Contact Information QDRII SRAM Stratix Memory Reference Platform Altera Contact Altera or your local Altera FAE QDRII SRAM Vendors Samsung Cypress NEC Related Links Stratix III Device I/O Connectivity External Memory Device Interfaces in Stratix II, Stratix, and Stratix GX Devices External Memory Device Interfaces in Cyclone II and Cyclone Devices External Memory Device Interfaces in APEX™ II Devices Altera's Signal Integrity Center Rate This Page   Related Links Signal Integrity Center Memory Solution Center Memory Interface Design On-Line Demonstration

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