Until now, all the various device manufacturers have had to use alternative versions of GDDR6 memory as a temporary solution, while they have long waited for GDDR7 to arrive with a real generational leap in bandwidth. Meanwhile, Samsung has revealed an important piece of the puzzle in its plans for this task. Samsung recently has approved GDDR7 RAM uses PAM-3 (3-level pulse amplitude modulation) signaling. This will help next generation graphics cards to double the GDDR6 data rate.
- Samsung’s increased investment in GDDR7 memory and long-term development of V-NAND
Conventional GDDR6 RAM – found in AMD’s new Radeon RX 7000 series – uses NRZ (no return to zero) signaling to achieve data rates between 14 and 24 Gbps. This process can carry signals with values of 0 or 1 for 1 bit per cycle. But newer GPUs, like Nvidia’s RTX 4000 series, have moved to GDDR6X, which is slightly faster at 18 to 23 Gbps. They do this using PAM-4, which can take 2 bits per cycle with values of 0, 1, 2, or 3.
Using PAM-3 is Samsung’s solution to bypass the restrictions
Samsung confirmed that the GDDR7 RAM it introduced at its Technology Day conference in October will hit 36Gbps, but recently revealed that it will achieve this with PAM-3 signaling, which strikes a balance between NRZ and PAM-4. The goal will be reached.
I’m not participating in this one, but here’s an interesting slide. Samsung confirms that GDDR7 uses PAM3 signaling.
NRZ is 0 or 1: 1 bit/cycle.
PAM3 is -1, 0, 1: 3 bits/2 cycles
PAM4 is 0, 1, 2, 3. 2 bits/1 cycle
80G Thunderbolt will also use PAM3.
— 𝐷’. 𝐼” 𝐶”””’ (@IanCutress) December 4, 2022
PAM-3 is at least 25% faster than NRZ
PAM-3 uses the values -1, 0, and 1 to achieve 3 bits every two cycles, or 1.5 bits per cycle. This alone is 25% more energy efficient than the higher bandwidth NRZ, but requires less equipment than PAM-4, making it cheaper. Intel’s Thunderbolt 5 cables also use PAM-3 signaling to deliver 80 Gbps bandwidth, double that of Thunderbolt 4.
Samsung also recently introduced another GDDR6 alternative called GDDR6W as a competitor to HBM2 memory. The company introduced HBM2 as a possible successor to GDDR6 with higher bandwidth and higher speed, but its implementation failed in AMD’s Vega series graphics cards, causing AMD to revert to the old GDDR6. The bandwidth of GDDR6W is far superior to GDDR6 and similar to HBM2. In addition, it can support the same manufacturing processes as GDDR6 products. Of course, Samsung’s announcements did not mention when GDDR7 will be available, but AMD and Nvidia could choose GDDR6W for their next series of graphics cards for now before moving to GDDR7.
Samsung’s slide showing PAM-3 for GDDR7 also mentions other new DRAM technologies such as T-Coul and Multiplexed Rank DIMM (MRDIMM). T-Coil can significantly increase IO speed, while MRDIMM can double the capacity. It is clear that Samsung is trying to revolutionize the memory industry.
- Mass production of Samsung UFS 4.0 memory this month for mobile devices
- Samsung starts development of DDR6 memory
- Introducing Samsung UFS 4.0 memory with higher speed and better energy efficiency
- Samsung looking to work with Qualcomm to improve its LPDDR5X memory