GDDR7 SDRAM


Graphics Double Data Rate 7 Synchronous Dynamic Random-Access Memory is a type of synchronous graphics random-access memory with a high-bandwidth, "double data rate" interface, designed for use in graphics cards and high-performance computing. It is a type of GDDR 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. Samsung announced two months later that it would use PAM-3 signaling to achieve the highest transfer rate.
  • On March 8, 2023, Cadence announced the verification solution tool for preliminary GDDR7 SDRAM production.
  • On June 30, 2023, Micron announced that it will be manufactured using 1β node, slated to release in H1 2024.
  • On July 18, 2023, Samsung announced the first generation of GDDR7, which can reach up to 32 Gbps per pin, 40% higher bandwidth compared to GDDR6 and 20% more energy efficient. For packaging material, it will use epoxy molding compound along with IC architecture optimization, which will reduce thermal resistance by 70%. Later, on a Q&A session, Samsung mentioned that it will be manufactured using D1z node 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.
  • On March 5, 2024, JEDEC published the GDDR7 Graphics Memory formal standard and specifications.

    Technologies

GDDR7 SDRAM uses three-level pulse-amplitude modulation, replacing GDDR6'S NRZ and GDDR6x's PAM-4. PAM-3 transfers three bits in two cycles, while NRZ transfers one bit in one cycle. PAM-3 is 20% more energy-efficient than NRZ while running at a higher bandwidth. Manufacturing equipment will be less costly than PAM-4.
GDDR7 adds on-die error correction code, error checking and scrubbing features for chip reliability, mainly useful for compute/AI use cases.
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, and chip capacities up to 64Gbit - compared to GDDR6X's 16Gbit.