For years, computer processor speeds have been increasing exponentially following Moore's law, but computer memory has not kept up. This has lead to a growing discrepancy between processor speeds and available memory bandwidth that's become known as the "memory wall."
In 2011, memory providers Micron (MU 0.23%) and Samsung proposed a new technology called the hybrid memory cube, or HMC, as a way of breaking through the memory wall. Now, in collaboration with longtime partner Intel (INTC +1.07%), Micron seems to be ready to bring HMC to wider adoption. What is this new technology, and will it really revolutionize computer memory?
The technology
The hybrid memory cube is an example of the emerging 3D trend in semiconductors, in which chips are stacked on top of each other in order to provide better connectivity and to take up less space. HMC consists of a stack of DRAM die that are connected by vertical electrical connections known as through-silicon vias. Currently, Micron can stack either 4 or 8 of the DRAM die to make 2GB or 4GB versions of the hybrid memory cube.
The hybrid memory cube. Source: Micron.
The DRAM stack rests on a logic layer, which handles all of the control within HMC. This further differentiates HMC from ordinary DRAM, which handles data only. According to Mike Black, technology strategist at Micron, the on-chip logic controller gives the HMC error correction, debug, and resiliency features that would normally have to be handled by the CPU.
There are several crucial benefits of this stacked, compact architecture. Most importantly, HMC provides 15 times the bandwidth of DDR3 DRAM, justifying Micron's claim that it is breaking through the memory wall. HMC also requires 70% less energy per bit compared to DDR3. Finally, it requires 90% less space than today's memory modules.
The collaboration with Intel
The memory wall has been most obvious in high-performance computing, so it is not surprising that the first applications for HMC have been in supercomputing. Last November, Micron collaborated with Fujitsu to display a supercomputer prototype using HMC technology at the Supercomputing 2013 Conference.
Then, earlier this month, Micron announced it will be providing a custom version of HMC for Intel's next-generation Xeon Phi processor, codenamed Knights Landing. HMC will be integrated on-package with the processor to provide the highest density and performance. The first application of the Knights Landing system, in a supercomputer named "Cori," will consist of 9,300 Knights Landing processors and will be built for the National Energy Research Scientific Computing Center in 2016.
What this means for investors
HMC could play a big role at Micron down the line. The company is moving away from selling commoditized components and toward higher-margin memory solutions that are optimized for customer applications. HMC is a perfect example of this, and according to CEO Mark Durcan, it is one of Micron's biggest growth opportunities in DRAM.
The Knights Landing collaboration with Intel suggests that Micron, which is sampling HMC now, will be bringing the hybrid memory cube to volume production soon. At first, HMC will likely be used in supercomputers and high-end servers. Packet processing is another likely application, and programmable-logic device makers Xilinx and Altera, who both do a lot of business in the networking space, already support Micron's HMC with their newest FPGAs.
Looking further down the line, it is probable that more and more computing environments will make use of HMC technology, as the discrepancy between processors and conventional memory continues to increase. Mid-range servers, laptops, and ultimately smartphones, which have strict limits on power consumption, will benefit from HMC's increased bandwidth and compact architecture.
In conclusion
With its significant improvements over current memory technology, the hybrid memory cube is poised to revolutionize computing over the next several years, starting with high-end applications and making its way down to more everyday workflows. Micron seems ready to bring HMC to volume production in the near future, and it will likely see significant growth thanks to this innovative technology.
