Double Data Rate 5 Synchronous Dynamic Random-Access Memory (DDR5 SDRAM) is the latest type of synchronous dynamic random-access memory. Compared to its predecessor DDR4 SDRAM, DDR5 was planned to reduce power consumption, while doubling bandwidth.[5] The standard, originally targeted for 2018,[6] was released on July 14, 2020.[2]

DDR5 SDRAM
Double Data Rate 5 Synchronous Dynamic Random-Access Memory
Type of RAM
16 GB[1] DDR5-4800 1.1 V UDIMM
DeveloperJEDEC
TypeSynchronous dynamic random-access memory
Generation5th generation
Release dateJuly 14, 2020; 3 years ago (2020-07-14)[2]
Standards
  • DDR5-4000 (PC5-32000)
  • DDR5-4400 (PC5-35200)
  • DDR5-4800 (PC5-38400)
  • DDR5-5200 (PC5-41600)
  • DDR5-5600 (PC5-44800)
  • DDR5-6000 (PC5-48000)
  • DDR5-6200 (PC5-49600)
  • DDR5-6400 (PC5-51200)
  • DDR5-6800 (PC5-54400)
  • DDR5-7200 (PC5-57600)
  • DDR5-7600 (PC5-60800)
  • DDR5-8000 (PC5-64000)
[3][4]
Clock rate2,000–4,000 MHz
Cycle time16n bank structure
Prefetch buffer4n
Transfer rate4–8GT/s
Bandwidth32–64 GB/s[a]
Voltage1.1 V nominal (actual levels are regulated by on-the-module regulators)
PredecessorDDR4 SDRAM (2014)
SuccessorDDR6 SDRAM

A new feature called Decision Feedback Equalization (DFE) enables input/output (I/O) speed scalability for higher bandwidth and performance improvement. DDR5 has about the same latency (around 14 ns) as DDR4 and DDR3.[7] DDR5 octuples the maximum DIMM capacity from 64 GB to 512 GB.[8][3] DDR5 also has higher frequencies than DDR4, up to 8GT/s which translates into 64 GB/s (8000 megatransfers/second * 64-bit width / 8 bits/byte = 64 GB/s) of bandwidth per DIMM.

Rambus announced a working DDR5 dual in-line memory module (DIMM) in September 2017.[9][10] On November 15, 2018, SK Hynix announced completion of its first DDR5 RAM chip; running at 5.2 GT/s at 1.1 V.[11] In February 2019, SK Hynix announced a 6.4 GT/s chip, the highest speed specified by the preliminary DDR5 standard.[12] The first production DDR5 DRAM chip was officially launched by SK Hynix on October 6, 2020.[13][14]

The separate JEDEC standard Low Power Double Data Rate 5 (LPDDR5), intended for laptops and smartphones, was released in February 2019.[15]

Compared to DDR4, DDR5 further reduces memory voltage to 1.1 V, thus reducing power consumption. DDR5 modules incorporate on-board voltage regulators in order to reach higher speeds.[10]

There is a general expectation that most use-cases that currently used DDR4 will eventually migrate to DDR5.

Features edit

Unlike DDR4, all DDR5 chips have on-die error correction code, where errors are detected and corrected before sending data to the CPU. This, however, is not the same as true ECC memory with extra data correction chips on the memory module. DDR5's on-die error correction is to improve reliability and to allow denser RAM chips which lowers the per-chip defect rate. There still exist non-ECC and ECC DDR5 DIMM variants; the ECC variants have extra data lines to the CPU to send error-detection data, letting the CPU detect and correct errors occurring in transit.[16]

Each DDR5 DIMM has two independent channels. Earlier DIMM generations featured only a single channel and one CA (Command/Address) bus controlling the whole memory module with its 64 (for non-ECC) or 72 (for ECC) data lines. Both subchannels on a DDR5 DIMM each have their own CA bus, controlling 32 bits for non-ECC memory and either 36 or 40 data lines for ECC memory, resulting in a total number of either 64, 72 or 80 data lines. The reduced bus width is compensated by a doubled minimum burst length of 16, which preserves the minimum access size of 64 bytes, which matches the cache line size used by modern x86 microprocessors.[17]

Memory modules edit

Multiple DDR5 memory chips can be mounted on a circuit board to form memory modules. For use in personal computers and servers, DDR5 memory is usually supplied in 288-pin dual in-line memory modules, more commonly known as DIMMs. As with previous memory generations, there are multiple DIMM variants available for DDR5.

Unbuffered memory modules (UDIMMs) directly expose the memory chip interface to the module connector. Registered or load-reduced variants (RDIMMs/LRDIMMs) use additional active circuitry on the memory module in order to buffer the signals between the memory controller and the DRAM chips. This reduces the capacitive load on the DDR5 bus.

DDR5 RDIMMs/LRDIMMs use 12 V and UDIMMs use 5 V input.[18] In order to prevent damage by accidental insertion of the wrong memory type, DDR5 UDIMMs and (L)RDIMMs are not mechanically compatible. Additionally, DDR5 DIMMs are supplied with management interface power at 3.3 V,[19][20] and use on-board circuitry (a power management integrated circuit[21] and associated passive components) to convert to the lower voltage required by the memory chips. Final voltage regulation close to the point of use provides more stable power, and mirrors the development of voltage regulator modules for CPU power supplies.

Operation edit

Standard DDR5 memory speeds range from 4000 to 6400 million transfers per second (PC5-32000 to PC5-51200).[3] Higher speeds may be added later, as happened with previous generations.

Compared to DDR4 SDRAM, the minimum burst length was doubled to 16, with the option of "burst chop" after eight transfers. The addressing range is also slightly extended as follows:

  • The number of chip ID bits remains at three bits, allowing up to eight stacked chips (3 → 3).
  • A third bank group bit (BG2) was added, allowing up to eight bank groups (2 → 3).
  • The maximum number of banks per bank group remains at four (2 → 2),
  • The number of row address bits remains at 17, for a maximum of 128K rows (17 → 17).
  • One more column address bit (C10) is added, allowing up to 8192 columns (1 KB pages) in ×4 chips (11 → 12).
  • The least-significant three column-address bits (C0, C1, C2) are removed. All reads and writes must begin at a column address which is a multiple of 8 (3 → 0). This is necessary due to the internal ECC.
  • 1 bit is reserved for addressing expansion as either a 4th chip ID bit (CID3) or an additional row address bit (R17) (0 → 1).

Command encoding edit

DDR5 command encoding[22][23]
Command CS Command/address (CA) bits
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Activate
(Open a row)
L L L Row R0–3 Bank Bank group Chip CID0–2
H Row R4–16 R17/
CID3
Reserved L L H Reserved
H Reserved
Reserved for future use L H L L L V
H V
Write pattern L H L L H L H Bank Bank group Chip CID0–2
H V Column C3–10 V AP H V CID3
Reserved for future use L H L L H H V
H V
Mode register write L H L H L L Address MRA0–7 V
H Opcode OP0-7 V CW V
Mode register read L H L H L H Address MRA0–7 V
H V CW V
Write L H L H H L BL Bank Bank group Chip CID0–2
H V Column C3–10 V AP WRP V CID3
Read L H L H H H BL Bank Bank group Chip CID0–2
H V Column C3–10 V AP V CID3
Vref CA L H H L L L Opcode OP0-6 L V
Vref CS L H H L L L Opcode OP0-6 H V
Refresh all L H H L L H CID3 V H L Chip CID0–2
Refresh management all L H H L L H CID3 V L Chip CID0–2
Refresh same bank L H H L L H CID3 Bank V H Chip CID0–2
Refresh management same bank L H H L L H CID3 Bank V L H Chip CID0–2
Precharge all L H H L H L CID3 V L Chip CID0–2
Precharge same bank L H H L H L CID3 Bank V H Chip CID0–2
Precharge L H H L H H CID3 Bank Bank group Chip CID0–2
Reserved for future use L H H H L L V
Self-refresh entry L H H H L H V L V
Power-down entry L H H H L H V H ODT V
Multi-purpose command L H H H H L Opcode OP0–7 V
Power-down exit,
No operation
L H H H H H V
Deselect (no operation) H X
  • Signal level
    • H, high
    • L, low
    • V, valid, either low or high
    • X, irrelevant
  • Logic level
    •   Active
    •   Inactive
    •   Unused
  • Control bits
    • AP, Auto-precharge
    • CW, Control word
    • BL, Burst length ≠ 16
    • WRP, Write partial
    • ODT, ODT remains enabled

The command encoding was significantly rearranged and takes inspiration from that of LPDDR4; commands are sent using either one or two cycles with 14-bit bus. Some simple commands (e.g. precharge) take one cycle, while any that include an address (activate, read, write) use two cycles to include 28 bits of information.

Also like LPDDR, there are now 256 8-bit mode registers, rather than eight 13-bit mode registers. Also, rather than one register (MR7) being reserved for use by the registered clock driver chip, a complete second bank of mode registers is defined (selected using the CW bit).

The "Write Pattern" command is new for DDR5; this is identical to a write command, but the range is filled in with copies of a one-byte mode register (which defaults to all-zero) instead of individual data. Although this normally takes the same amount of time as a normal write, not driving the data lines saves energy. Also, writes to multiple banks may be interleaved more closely as the command bus is freed earlier.

The multi-purpose command includes various sub-commands for training and calibration of the data bus.

Support edit

Intel edit

The 12th generation Alder Lake and 13th generation Raptor Lake Core CPUs support both DDR5 and DDR4 but, usually, there are only DIMM sockets for either one or the other on a motherboard. Some mainboards with Intel's H610 chipset support both DDR4 and DDR5, but not simultaneously.[24]

Sapphire Rapids server CPUs support DDR5 but not DDR4.

AMD edit

DDR5 and LPDDR5 are supported by the Ryzen 6000 series mobile APUs, powered by their Zen 3+ architecture. Ryzen 7000 series desktop processors also support DDR5 memory as standard.[25]

Epyc fourth-generation Genoa and Bergamo server CPUs have support for 12-channel DDR5 on the SP5 socket.[26][27]

Notes edit

  1. ^ 64 GB/s assumes 8 GT/s, each with 64 bits of bus width, then divided by 8 to convert from bits to bytes

References edit

  1. ^ Here, K, M, G, or T refer to the binary prefixes based on powers of 1024.
  2. ^ a b Smith, Ryan (July 14, 2020). "DDR5 Memory Specification Released: Setting the Stage for DDR5-6400 And Beyond". AnandTech. Retrieved July 15, 2020.
  3. ^ a b c "DDR5 Memory Standard: An introduction to the next generation of DRAM module technology - Kingston Technology". Kingston Technology. Retrieved February 19, 2023.
  4. ^ "DDR5 SDRAM Product Core Data Sheet" (PDF). Micron. Retrieved April 4, 2023.
  5. ^ Manion, Wayne (March 31, 2017). "DDR5 will boost bandwidth and lower power consumption". Tech Report. Retrieved April 1, 2017.
  6. ^ Cunningham, Andrew (March 31, 2017). "Next-generation DDR5 RAM will double the speed of DDR4 in 2018". Ars Technica. Retrieved January 15, 2018.
  7. ^ Dr. Ian Cutress. "Insights into DDR5 Sub-timings and Latencies". AnandTech.
  8. ^ "DDR5 vs DDR4 – All the Design Challenges & Advantages".
  9. ^ Lilly, Paul (September 22, 2017). "DDR5 memory is twice as fast as DDR4 and slated for 2019". PC Gamer. Retrieved January 15, 2018.
  10. ^ a b Tyson, Mark (September 22, 2017). "Rambus announces industry's first fully functional DDR5 DIMM - RAM - News". hexus.net.
  11. ^ Malakar, Abhishek (November 18, 2018). "SK Hynix Develops First 16 Gb DDR5-5200 Memory Chip". Archived from the original on March 31, 2019. Retrieved November 18, 2018.
  12. ^ Shilov, Anton. "SK Hynix Details DDR5-6400". anandtech.com.
  13. ^ "SK hynix Launches World's First DDR5 DRAM". hpcwire.com.
  14. ^ "SK hynix: DDR5 DRAM Launches". businesskorea.co.kr. October 7, 2020.
  15. ^ "JEDEC Updates Standard for Low Power Memory Devices: LPDDR5" (Press release). JEDEC. February 19, 2019.
  16. ^ Cutress, Ian, Why DDR5 does NOT have ECC (by default), retrieved August 7, 2021
  17. ^ "Introducing Micron® DDR5 SDRAM: More Than a Generational Update" (PDF). Retrieved July 10, 2023.
  18. ^ "DDR5 SDRAM UDIMM Core: Product Description" (PDF). Micron Technology, Inc. p. 1. Archived from the original (PDF) on December 25, 2023. Voltage (external supply, nominal) / VIN_Bulk: 5V / Bulk input DC supply voltage from system
  19. ^ "P8900 PMIC for DDR5 RDIMMs and LRDIMMs". Renesas. Retrieved July 19, 2020.
    "P8911 PMIC for Client DDR5 Memory Modules". Renesas. Retrieved July 19, 2020.
  20. ^ "DDR5 SDRAM RDIMM Based on 16Gb M-die" (PDF). SK Hynix. p. 7. Archived from the original (PDF) on October 29, 2021. Retrieved October 29, 2021. VIN_BULK[:] 12 V power input supply pin to the PMIC. VIN_MGMT[:] 3.3 V power input supply pin to the PMIC for VOUT_1.8V & VOUT_1.0V LDO output,side band management access, internal memory read opera- tion.
  21. ^ US patent 10769082, Patel, Shwetal Arvind; Zhang, Andy & Meng, Wen Jie et al., "DDR5 PMIC Interface Protocol and Operation", published 2019-11-07, assigned to Integrated Device Technology, Inc. 
  22. ^ "JEDEC DDR5 SDRAM Specification". JEDEC committee JC42.3. Retrieved May 15, 2023.
  23. ^ "Micron DDR5 SDRAM Specification" (PDF). Micron Technology Inc. Retrieved May 15, 2023.
  24. ^ "DDR4 und DDR5: H610-Mainboard kombiniert beide Speicher-Generationen".
  25. ^ Copeman, Anyron (June 15, 2023). "Everything you need to know about the AMD Ryzen 7000 Series". Tech Advisor. Archived from the original on June 17, 2023. Retrieved June 28, 2023.
  26. ^ Goetting, Chris (November 10, 2022). "AMD 4th Gen EPYC 9004 Series Launched: Genoa Tested In A Data Center Benchmark Gauntlet". HotHardware. Retrieved June 28, 2023.
  27. ^ Goetting, Chris (June 13, 2023). "AMD Unleashes EPYC Bergamo And Genoa-X Data Center CPUs, AI-Ready Instinct MI300X GPUs". HotHardware. Retrieved June 28, 2023.

External links edit