GDDR7 SDRAM

GDDR7 SDRAM
Graphics Double Data Rate 7 Synchronous Dynamic Random-Access Memory
Type of RAM
Developer	JEDEC
Type	Synchronous dynamic random-access memory
Generation	7th generation
Release date	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 1β 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 (100% higher bandwidth per pin compared to 16 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^[6]) 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.^[7]
On March 5, 2024, JEDEC published the GDDR7 Graphics Memory formal standard and specifications.^[8]

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.^[9]

GDDR7 adds on-die error correction code, error checking and scrubbing features for chip reliability, mainly useful for compute/AI use cases.^[10]

Initial data rates are at 32 Gbps/pin, while memory manufacturers have noted that rates up to 36 Gbps/pin are readily attainable. The standard has future bandwidth up to 48 Gbps/pin,^[11] and chip capacities up to 64 Gbit - compared to GDDR6X's 16 Gbit.^[10]