JESD305-R4-RCF_v12022DDR5RDIMMStandard,AnnexF.pdf

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DDR5 RDIMM标准，全称为“双倍数据速率第五代同步动态随机存取内存（Double Data Rate Fifth Generation Synchronous Dynamic Random-Access Memory）寄存器式DIMM标准”，是JEDEC固态技术协会（JEDEC Solid State Technology Association）制定的一系列规范之一，旨在推动内存技术的发展和兼容性。该标准的Annex F部分详细阐述了DDR5 RDIMM的特定技术和设计要求。 DDR5内存相比其前一代DDR4，提供了更高的带宽、更低的功耗以及增强的错误纠正能力。以下是一些关键知识点： 1. **带宽提升**：DDR5内存的数据传输速率显著提高，初始规格支持4800MT/s，后续可扩展至6400MT/s以上，远超DDR4的最高3200MT/s。 2. **模块化设计**：DDR5内存引入了更精细的Bank Group结构，每个DIMM上的DRAM芯片被分为多个Bank Group，可以并行处理更多的数据请求，提高了内存的并发性能。 3. **电压降低**：DDR5内存的工作电压从DDR4的1.2V降至1.1V，有助于降低系统功耗，适应数据中心和高性能计算场景的能效需求。 4. **电源管理集成**：DDR5内存模组内集成了电源管理集成电路（PMIC），负责为DRAM芯片提供精确的电压控制，确保稳定运行并降低电磁干扰。 5. **增强的错误检测与校正**：DDR5引入了增强的ECC（Error Correction Code）功能，如内置的Chipkill技术，可以保护数据免受单个或多个内存芯片故障的影响，提高了系统的可靠性。 6. **On-Die Termination（ODT）**：DDR5内存的内部终结电阻（ODT）集成在DRAM芯片内部，减少了外部组件，降低了信号反射，提高了信号完整性。 7. **命令复用**：DDR5内存支持命令和地址线的复用，即在一个时钟周期内可以处理更多命令，提升了内存控制器的效率。 8. **热管理**：DDR5标准可能包含了更高级的热管理特性，确保在高负荷运行下内存能够保持稳定工作温度。 9. **模块兼容性**：尽管DDR5内存引脚布局发生了变化，但JEDEC标准确保了新模块与现有主板的兼容性，通常通过适配器或新型主板来实现。 10. **测试与验证**：JEDEC DDR5标准定义了严格的测试和验证流程，确保所有符合标准的DDR5 RDIMM内存都能达到规定的性能和稳定性要求。 DDR5 RDIMM标准代表了内存技术的最新进展，它不仅提高了数据传输速度，还引入了一系列改进以提高系统性能、降低功耗和增强稳定性。JEDEC的这个标准为制造商提供了一个清晰的框架，确保不同厂商的产品可以无缝配合，同时也为消费者提供了选择合适内存产品的依据。

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JEDEC

STANDARD

DDR5 RDIMM Standard Annex F

JESD305-R4-RCF

Version 1.0

APRIL 2022

JEDEC SOLID STATE TECHNOLOGY ASSOCIATION

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JEDEC

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JEDEC

JEDEC Standard No. 305-R4-RCF

Version 1.0

-i-

DDR5 RDIMM STANDARD ANNEX F

Contents

Page

1 Scope ................................................................................................................................................. 1

2 DDR5 Registered DIMM Design File .............................................................................................. 1

3 Module Configuration ....................................................................................................................... 1

4 SDRAM Configuration ..................................................................................................................... 2

5 Supported Speeds .............................................................................................................................. 2

6 Design Deviations ............................................................................................................................. 2

7 General Layout .................................................................................................................................. 3

8 Functional Block Diagram ................................................................................................................ 4

9 SMBus Net Structures ....................................................................................................................... 8

10 Clock Input Net Structure ................................................................................................................. 8

11 Register Clock Output Net Structure ................................................................................................ 9

12 Data Net Structure – DQ, CB, DQS_t, and DQS_c ........................................................................ 10

13 Post Register Address and Command Net Structure Routing ......................................................... 12

14 Post Register Control Net Structure Routing .................................................................................. 13

15 Pre-Register Address, Command, and Parity Net Structure Routing .............................................. 14

16 DIMM Impedance Profile ............................................................................................................... 15

17 RESET_n and QRST_n Net Structure Routing .............................................................................. 16

18 ALERT_n Output Net Structure Routing ........................................................................................ 16

19 DERROR_in_n Net Structure Routing ........................................................................................... 17

20 Function Control Word Programming............................................................................................. 18

21 Cross Section Recommendations .................................................................................................... 19

Tables

Table 1 — DDR5 Registered DIMM Design File ............................................................................................... 1

Table 2 — Module Configuration ................................................................................................

........................ 1

Table 3 — SDRAM Configuration ...................................................................................................................... 2

Table 4 — Supported Speeds ............................................................................................................................... 2

Table 5 — Design Deviations .............................................................................................................................. 2

Table 6 — SMBus Net Structures ........................................................................................................................ 8

Table 7 — Clock Lengths for Register Input Net Structures ............................................................................... 8

Table 8 — Trace Lengths for Register Clock Output to SDRAM Load Net Structures ...................................... 9

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JEDEC