GDDR7 SDRAM explained

Abbr:	GDDR7 SDRAM
Graphics Double Data Rate 7 Synchronous Dynamic Random-Access Memory
Developer:	JEDEC
Type:	Synchronous dynamic random-access memory
Generation:	7th generation
Release:	5 March 2024
Predecessor:	GDDR6 SDRAM

Graphics Double Data Rate 7 Synchronous Dynamic Random-Access Memory (GDDR7 SDRAM) is a type of synchronous graphics random-access memory (SGRAM) specified by the JEDEC Semiconductor Memory Standard, with a high bandwidth, "double data rate" interface, designed for use in graphics cards, game consoles, and high-performance computing. It is a type of GDDR SDRAM (graphics DDR SDRAM), and is the successor to GDDR6.

History

• At Samsung Tech Day 2022, Samsung announced GDDR7 as the successor of GDDR6X, which could deliver up to 36 GT/s.^[1] Samsung announced two months later that it would use PAM-3 signaling to achieve the highest transfer rate.^[2]
• On March 8, 2023, Cadence announced the verification solution tool for preliminary GDDR7 SDRAM production.^[3]
• On June 30, 2023, Micron announced that it will be manufactured using 1ß node (equivalent to 12–10 nm process node), slated to release in H1 2024.^[4]
• On July 18, 2023, Samsung announced the first generation of GDDR7, which can reach up to 32 Gbps per pin (33% higher bandwidth per pin compared to 24 Gbps per pin on GDDR6), 40% higher bandwidth (1.5 TB/s) compared to GDDR6 (1.1 TB/s) and 20% more energy efficient. For packaging material, it will use epoxy molding compound (EMC) along with IC architecture optimization, which will reduce thermal resistance by 70%.^[5] Later, on a Q&A session, Samsung mentioned that it will be manufactured using D1z node (equivalent to 15–14 nm) and will operate on 1.2V. A 1.1V version with reduced clockspeeds will also be made available at some point in to the future after the release of the 1.2V version.^[6]
• On March 5, 2024, JEDEC published the GDDR7 Graphics Memory formal standard and specifications.^[7]

Technologies

GDDR7 SDRAM employs PAM-3 signaling (three-level pulse-amplitude modulation) rather than NRZ. PAM-3 is 20% more energy-efficient than NRZ while running at a higher bandwidth. Manufacturing equipment will be less costly than PAM-4. PAM-3 processes 1.58 bits per cycle, while NRZ processes only 1 bit per cycle.^[8] GDDR7 SDRAM also will be manufactured using 1ß node (equivalent to 12–10 nm process node), which will be the last DRAM production process that will rely on deep ultraviolet (DUV) lithography tools; future devices will be produced using extreme ultraviolet lithography (EUV).

GDDR7 adds on-die error correction code, error checking and scrubbing features for chip reliability, mainly useful for compute/AI use cases.^[9]

Initial data rates are at 32Gbps/pin, while memory manufacturers have noted that rates up to 36Gbps/pin are readily attainable. The standard has future bandwidth up to 48Gbps/pin,^[10] and chip capacities up to 64Gbit - compared to GDDR6X's 16Gbit.^[9]

See also

• List of interface bit rates

Notes and References

1. Web site: 2022-10-06 . Samsung announces 36 Gbps GDDR7 memory standard, aims to release V-NAND storage solutions with 1000 layers by 2030 . 2023-06-30 . Notebookcheck . en.
2. Web site: Discuss . btarunr . 2022-12-05 . Samsung Reveals GDDR7 Memory Uses PAM3 Signalling to Achieve 36 Gbps Data-Rate . 2023-06-30 . TechPowerUp . en.
3. Web site: Cadence announces first GDDR7 verification solution . 2023-06-30 . VideoCardz.com . en-US.
4. Web site: 2023-06-30 . Micron could introduce GDDR7 memory chips in early 2024 . 2023-06-30 . TechSpot . en-US.
5. Web site: 2023-07-19 . Samsung develops industry's first GDDR7 DRAM with 1.5 TBps bandwidth . 2023-07-31 . Notebookcheck . en.
6. Web site: Smith . Ryan . Samsung Completes Initial GDDR7 Development: First Parts to Reach Up to 32Gbps/pin . 2023-07-31 . www.anandtech.com.
7. Web site: JEDEC Publishes GDDR7 Graphics Memory Standard JEDEC . 2024-03-05 . www.jedec.org.
8. Web site: Anton Shilov . GDDR7 Arrives: Samsung Outs World's First Chip, 32 GT/s for Next-Gen GPUs . en . . 2023-07-19 . 2023-10-06.
9. Web site: Shilov . Anton . Micron's GDDR7 Chip Smiles for the Camera as Micron Aims to Seize Larger Share of HBM Market . 2024-06-09 . www.anandtech.com.
10. Web site: Smith . Anton Shilov, Ryan . JEDEC Publishes GDDR7 Memory Spec: Next-Gen Graphics Memory Adds Faster PAM3 Signaling & On-Die ECC . 2024-06-09 . www.anandtech.com.