Ofelia Plads, Kvæsthusbroen, København, Danmark — photo by — @kaspercph

Ferroelectric RAM vs. MRAM

What oppositional advantages and disadvantages are there?

FeRAM is one of a growing number of alternative non-volatile random-access memory technologies that offer the same functionality as flash memory.

“FRAM, FeRAM or Ferroelectric Random Access Memory uses a ferroelectric capacitor architecture that employs ferroelectric materials as storage elements. These materials have an intrinsic electric dipole switched into opposite polarities with an external electric field. Switching the ferroelectric polarization states requires the movement of the dipole located within an oxygen octahedron in response to an electric field.”

Ferroelectric RAM was proposed by MIT graduate student Dudley Allen Buck in his master’s thesis, Ferroelectrics for Digital Information Storage and Switching, published in 1952. The story of Dr. Dudley Allen Buck could be a cold war thriller. He was a code breaker and was working on the cryotron with the idea of switching between 1s and 0s — an idea that may have contributed at least partly to modern computing. He thought of using magnetic cores as well as and became a professor at MIT. Sadly he died at the young age of 32, some believed he was assassinated by KGB, although there is little proof to substantiate this claim.

The advantages of FeRam

FeRAM’s advantages over Flash include:

  • Lower power usage.
  • Faster write performance.
  • A much greater maximum read/write endurance
  • FeRAMs have data retention times of more than 10 years at +85 °C (up to many decades at lower temperatures).

The disadvantages

  • Much lower storage densities than flash devices, storage capacity limitations and higher cost.
  • Like DRAM, FeRAM’s read process is destructive, necessitating a write-after-read architecture.

One of the first commercial applications of FeRam was curiously enough in Playstation 2.

“The earliest known commercial product to use FeRAM is Sony’s PlayStation 2 (PS2), released in 2000. The PS2 hardware’s Emotion Engine central processing unit (CPU) manufactured by Toshiba contains 32 kb embedded FeRAM fabricated using a 500 nm complementary MOS (CMOS) process.”

One of the manufacturers of this is Cypress Semiconductors.

Cypress F-RAM

“Cypress F-RAM is built on Ferroelectric technology. The F-RAM chip contains a thin ferroelectric film of lead zirconate titanate, commonly referred to as PZT. The atoms in the PZT change polarity in an electric field, thereby producing a power efficient binary switch. However, the most important aspect of the PZT is that it is not affected by power disruption, making F-RAM a reliable nonvolatile memory. A common misconception is that ferroelectric crystals are ferromagnetic or have similar magnetic properties. In fact, ferroelectric materials switch in an electric field and are not affected by magnetic fields.”

A different company manufacturing MRAM would of course argue otherwise. This company is called Everspin.

FRAM vs. MRAM?

Why Replace a Ferroelectric RAM with an MRAM?

“MRAM has unlimited endurance and infinite Read/Write cycles; FRAM Reads are destructive and eventually lead to wear-out.

MRAM Read/Write Cycle and Access times are faster, 35ns vs. 60ns access time, 35ns vs. 115ns cycle time.

MRAM is not subject to imprint.

MRAM provides data retention for 20 years.

MRAM is scalable. Toggle MRAM available up to 16Mb. FRAM is stalled at 4Mb.”

“Magnetoresistive random-access memory is a type of non-volatile random-access memory which stores data in magnetic domains. Developed in the mid-1980s, proponents have argued that magnetoresistive RAM will eventually surpass competing technologies to become a dominant or even universal memory.”

Magnetoresistive RAM (MRAM)

Magnetoresistive RAM is inherently non-volatile, has unlimited endurance with no known wear-out mechanism and is not subject to data loss at higher temperature operating conditions.

Again according to Everspin this is why you should change to MRAM:

  • “Everspin MRAM is available in a functional equivalent or drop-in replacement for most FRAM devices.
  • Immediate (<1ns) Power-off with no loss of data.
  • Unlimited read and write cycle endurance.
  • Truly Asynchronous SRAM compatible speeds and cycle times.
  • 20-Year data retention with no cycling dependence.
  • No wear-out concerns.”

Is the wear-out concerns founded?

It would be interesting to talk to an expert.

This article was not comprehensive, however I am simply attempting to understand the subject to a larger extent.

Memory technologies can be relevant to most compute, however I consider it important in the context of artificial intelligence.

This is #500daysofAI and you are reading article 321. I am writing one new article about or related to artificial intelligence every day for 500 days. My focus for day 300–400 is about AI, hardware and the climate crisis.

AI Policy and Ethics at www.nora.ai. Student at University of Copenhagen MSc in Social Data Science. All views are my own. twitter.com/AlexMoltzau

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