Magnetic Cores To MRAM: Nonvolatile Tipping Point?

May 12, 2010
It's back to the future with magnetic non-volatile primary storage. Operating systems and embedded applications will need to handle multiple memory types.

Burroughs 5500 magnetic core memory

Magnetic core storage used to be everywhere, from mainframes like the Burroughs B5500 (see the figure) to minicomputers. Back then, micros were just a gleam in someone’s eye. These days, 3- by 3-mm, 8- and 16-bit flash micros are the same size as many of the magnetic cores.

Magnetic core memory gave way to a variety of technologies, leading to the current mixture of ROM, EEPROM and nonvolatile RAM (NVRAM), flash memory, SRAM, and dynamic RAM. Life was much easier when only one type of memory was used.

NAND and NOR flash are the mainstays for large-capacity nonvolatile solid-state storage these days. They are even challenging rotating magnetic media as capacities grow and costs fall. NOR flash still has the edge with a much higher capacity limit, but it is getting to the point where more applications can get by with flash capacities and pricing.

The big challenges for flash are wear leveling and write performance. Wear leveling has spawned a host of software and hardware solutions designed to overcome the deficiencies of flash.


Nonvolatile memory technologies such as magnetoresistive RAM (MRAM), ferroelectric RAM (FRAM), and phase change memory look to challenge flash’s dominance. They may eventually challenge RAM’s cost, capacity, and speed.

Phase change memory from Numonyx (see “Thanks For The Memory”) and Unity Semiconductor are relatively new, but they look to reduce the limitations of flash memories while providing superior performance. Unity Semiconductor’s CMOx phase change memory eliminates the need for a transistor per storage cell (see“Nonvolatile Storage Doesn’t Require Transistors”).

FRAM appears to be taking on applications that currently use EEPROM that come in smaller capacities. Ramtron microcontrollers blend FRAM with flash and SRAM (see “Microcontrollers Commit To FRAM”).

Everspin is now delivering a family of 16-Mbit MRAM chips. Its earlier serial peripheral interface (SPI) and parallel MRAM chips had lower capacities that were suitable for storing configuration information, though these new parts move MRAM into primary storage.

Many applications such as RAID SAS controllers will utilize these chips for large data caches. However, a single 2-Mbyte chip is also sufficient for handling operating systems like Linux. It is actually large enough to handle code and data for a wide range of real-time operating systems (RTOSs) as well.


The potential movement from data storage to program and data storage moves magnetic memory back to its roots. It is still a long way from the uniform use of core memory within a system. Yet there are significant advantages to nonvolatile storage that operates as fast as SRAM with no write penalty and an unlimited lifetime.

The challenge is whether applications and OSs will coherently address large blocks of nonvolatile storage like MRAM or one of the other challengers. There is already some support for flash within a hierarchical memory environment, but flash often is viewed as block storage. MRAM and RAM can coexist with the same performance features where the only difference is nonvolatility and a higher resistance to alpha particles.

Instant-on and instant-off operation can benefit from nonvolatile storage, though integration with the OS will be necessary to allow applications to take advantage of this memory. This would allow critical data structures and application code to be retained between power cycles.

Simply having the ability to allocate and deallocate nonvolatile memory is just the first step. Applications would need to be written to account for this ability. Likewise, memory allocators and process initiation will need to be adjusted accordingly. The results could be interesting. 

•  Everspin

•  Numonyx

•  Ramtron

•  Unity Semiconductor

Sponsored Recommendations

TTI Transportation Resource Center

April 8, 2024
From sensors to vehicle electrification, from design to production, on-board and off-board a TTI Transportation Specialist will help you keep moving into the future. TTI has been...

Cornell Dubilier: Push EV Charging to Higher Productivity and Lower Recharge Times

April 8, 2024
Optimized for high efficiency power inverter/converter level 3 EV charging systems, CDE capacitors offer high capacitance values, low inductance (< 5 nH), high ripple current ...

TTI Hybrid & Electric Vehicles Line Card

April 8, 2024
Components for Infrastructure, Connectivity and On-board Systems TTI stocks the premier electrical components that hybrid and electric vehicle manufacturers and suppliers need...

Bourns: Automotive-Grade Components for the Rough Road Ahead

April 8, 2024
The electronics needed for transportation today is getting increasingly more demanding and sophisticated, requiring not only high quality components but those that interface well...


To join the conversation, and become an exclusive member of Electronic Design, create an account today!