September 3rd, 2024

The Memory Wall: Past, Present, and Future of DRAM

The article highlights the challenges facing DRAM, including slowed scaling, rising AI-driven memory demand, and high costs of HBM, while emphasizing the need for innovation and new memory technologies.

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The Memory Wall: Past, Present, and Future of DRAM

The article discusses the current state and future prospects of Dynamic Random Access Memory (DRAM), highlighting the challenges it faces in scaling and innovation. It notes that while Moore's Law has historically applied to DRAM, its scaling has significantly slowed, with density increases dropping from a doubling every 18 months to just 2x over the past decade. This stagnation is particularly problematic as the demand for memory, driven by advancements in artificial intelligence (AI), continues to grow. High Bandwidth Memory (HBM), essential for AI applications, is becoming increasingly expensive, comprising a large portion of manufacturing costs. The article explores potential solutions to the "memory wall," including extending the HBM roadmap and developing new memory technologies like Compute-in-Memory (CIM) and 3D DRAM. It emphasizes the need for innovation in DRAM to keep pace with improvements in logic chips, which are outpacing memory advancements. The article concludes by underscoring the importance of addressing these challenges to support the evolving demands of computing.

- DRAM scaling has slowed significantly, with only a 2x increase in density over the last decade.

- The rise of AI is increasing demand for memory, particularly High Bandwidth Memory (HBM), which is costly.

- Potential solutions to the memory wall include new memory technologies and extending existing roadmaps.

- Innovation in DRAM is crucial to match the advancements in logic chips.

- The DRAM industry faces economic and performance bottlenecks that need to be addressed.

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Link Icon 8 comments
By @magicalhippo - 7 months
Back when I was young, which isn't that far ago, one tried to put as much pre-computed stuff into memory as it was much faster than the CPU. Lookup tables left, right and center.

These days you can do thousands of calculations waiting for a few bytes of memory. And not only is the speed difference getting worse, but memory sizes aren't keeping up.

Guess we're not far away from compressing stuff before putting it in memory is something you'd want to do most of the time. LZ4 decompression[1] is already just a factor of a few away from memcpy speed.

[1]: https://github.com/lz4/lz4

By @ksec - 7 months
I have been stating this for at least 12+ years now. On HN and in many places. And it is still not common knowledge. Hopefully this article get spread and reposted many times in the future.

DRAM isn't getting (much) cheaper. And it will continue to be the case in next 10 years. Considering there is nothing on the roadmap to suggest any breakthrough.

People old enough may remember in the late 00s and even up to mid 10s, there are words like we will get 16GB computer as baseline, or I could work with 64GB soon.

Reality is that DRAM price has fluctuate lately within the same range in the past ~13 years. It was only in 2023 the price floor broke through the $2/GB barrier.

Unless we somehow found a way that could magically shrink the capacitor by a substantial amount. Or we change the way we do programming.

By @imtringued - 7 months
I'm curious if it is possible to design an AI accelerator built around ROM that is programmable via maskless lithography. The idea being that 90% of the chip is being produced using conventional mask based semiconductor technology, but the data is written through electron beam lithography.

Given a regular ROM structure on the silicon wafer, it would be possible to take advantage of parallel beams and design an electron beam lithography machine specifically for ROM to reduce the cost of programming. The final frontier would be to build a "wafer scale engine"-esque single wafer chip and we would have essentially reached the limits of what is achievable through clever design of silicon based semiconductors.

By @sevensor - 7 months
Compute in memory is exciting, but it’s going to be hard to pull off. Transistors go underneath capacitors, which means they have to survive the subsequent fabrication of the capacitors without thermal processing disrupting their carefully engineered dopant profiles. It’s not just conservatism that keeps on die logic simple. Bonding, as suggested by the article, is probably the only option, but that brings some absolutely hilarious alignment issues along with it. I’m sure it’s coming, but it won’t be cheap.
By @rayiner - 7 months
Can someone explain like I’m five why DRAM latency basically hasn’t improved in decades? I remember 60ns FPM SIMMs in our 486 back in the 1990s. Doesn’t seem any faster now.
By @hulitu - 7 months
What happened to SRAM ?
By @deater - 7 months
if Sally Mckee, who coined the term "Memory Wall", had a nickel for each time it gets mentioned, she'd have a lot of nickels
By @didgetmaster - 7 months
I think that 'memory wall' is completely different from 'memory hole', but I forget how.