Introduction
Each major transition in memory technology has been coupled with a revolution in system architectures that build on the key advantages of new memory technologies. NAND flash holds a strong position in the market, but there are potentially new non-volatile memory technologies on the horizon that can help address the demands of the data center and the mobile consumer.
The Storage Memory Revolution
The popularity of smartphones and tablets, those devices that are cloud-centric and have storage-hungry applications, has created a greater need for reliable storage memory solutions that provide high-capacity, power-efficiency and are cost-effective.
We view this next revolution in the form of a storage stack. This stack demonstrates the various technologies that are affected by any change in the bitcell, the basic building block of any memory technology.
With core technology at the foundation of the storage stack, Rambus is well positioned to address and develop additional technologies up through the system layers.
What is Non-Volatile Memory (NVM)?
NVM is a memory that is used when there is a need to retain stored information even after the power is turned off. NVM technologies include computer hard disks, or solid-state memory technologies like NAND flash memory.
The Stack
NVM Bitcell
With the growth of mobile and server applications, the need for improved capacity, higher performance and lower power memory systems has emerged.
NAND flash, a type of bitcell, has proven to be an affordable NVM storage solution especially for consumer electronics. This technology has historically scaled to deliver higher performance while closing the gap in cost per gigabyte; however, there are limitations that arise as the cell continues to shrink in size. Limitations such as performance, power efficiency, program and erase endurance and data retention time all decline as density increases and cell size decreases.
A primary concern among these limitations is the potential for loss of data, which is of great importance as the amount of critical data stored in NVM increases. Of the types of non-volatile memory, RRAM stands out among the potential NAND replacement contenders as it offers higher capacity at a low cost with the ability to scale.
Design and Architecture
If we apply changes to the bitcell, the overall NVM chip architecture has to change as well. A shift from NAND to RRAM bitcell topology will require a change in the chip architecture to accommodate the new bitcell.
NVM Interface
As the bitcell and memory architecture improves the performance and speed of the memory device, the NVM interface requires a faster data rate. RRAM has the capability to perform faster than traditional NAND memory types to accommodate the higher speed.
NVM Handling
The functions used for NVM handling, such as error correction code (ECC), block management, data encoding and decoding, and counter bit-to- bit interference, are specific to NAND. As a new bitcell is introduced, new NVM handling routines are required.
Storage Interface
Finally, the storage interface must support the fast speed achieved via the entire stack modification. This will lead to new protocols and increased performance.
Change is Inevitable!
Future NVM solutions will, no doubt, adopt the smallest cell size with highest performance. Scalability will be critical for addressing the needs of mobile and data storage markets. Rambus is ready for this change. Are you?
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