Other Current Memory Technologies

Early Computer Memories

Ryszard Milewicz' photo of Core MemoryMy colleague Lane Mason found an interesting history of memories blog post that answers the question: ” What did early computers use for fast read/write storage?”

The post in the Hackaday blog, written by Al Williams, covers drum memories, the Williams Tube and its competitor the Selectron (both briefly discussed in my earlier 3D XPoint post), mercury delay lines, dekatrons, core memory (the original Storage Class Memory), plated wire memory, twistor memory, thin-film memory, and bubble memory.

It also links to interesting videos about these devices.

Think of this as a companion piece to the EE Times memory history slideshow I covered in an earlier post.  It’s a fun and educational read!

A 1T SRAM? Sounds Too Good to be True!

Zeno 1T SRAMAt the IEEE’s International Electron Device Meeting (IEDM) in December a start-up named Zeno Semiconductors introduced a 1-transistor (1T) SRAM.  Given that today’s SRAMs generally use between six and eight transistors per bit, this alternative promises to squeeze the same amount of SRAM into a space 1/6th to 1/8th the size of current SRAM designs, leading to significant cost savings.

The device is really a single standard NMOS transistor that behaves as if it were two bipolar transistors connected into something like a flip-flop, although the transistors’ bases are open, rather than cross-coupled to the opposite transistors’ collector, as is done in a standard flip-flop.

The cell is selected by activating the gate, and the bit is set or sensed via the source and drain to provide a differential signal.

This is a decidedly clever departure from standard SRAM configurations, and it reflects a careful observation of the actual Continue reading

How Many Kinds of Memory Are There?

Micron's History of Memory TechnologiesWith Micron & Intel’s July 28 introduction of their new 3D XPoint memory both companies touted that his is the first new memory in a long time, and that the list of prior new memory types is short.

How short is that list?  Interestingly, Intel and Micron have different lists.  The Micron list, shown in this post’s graphic (click to enlarge), cites seven types: “Ram” (showing a vacuum tube), PROM, SRAM, DRAM, EPROM, NOR flash, and NAND flash.  Intel’s list adds magnetic bubble memory, making it eight.  (Definitions of these names appear in another Memory Guy blog post.)

The Memory Guy finds both lists puzzling in that they left out a number of important technologies.

For example, why did Intel neglect EEPROM, which is still in widespread use?  EEPROMs (or E²PROMs) are not only found in nearly every application that has a serial number (ranging from WiFi routers to credit cards), requires calibration (like blood glucose monitoring strips and printer ink cartridges), or provides operating parameters (i.e. the serial presence detect – SPD – in DRAM DIMMs), but they still ship in the billions of units every year.  In its time EEPROM was an important breakthrough.  Over the years EEPROM has had a much greater impact than has PROM.

And, given that both companies were willing to include tubes, a non-semiconductor technology, why did both Continue reading

Avalanche Samples MRAM


Today Avalanche Technology announced that it is sampling MRAM, making it the world’s second company to actually produce this much-researched technology.

For those unfamiliar with MRAM, it is one of a number of technologies being positioned to replace currently-entrenched memory technologies once they reach their scaling limits.  Regular Memory Guy readers know that this juncture has been anticipated for a few decades, but always seems to get postponed.

MRAM, like many other alternative technologies, offers the promise of scaling beyond the limits of DRAM and NAND to become cheaper than ether of these technologies.  Add to this its fast write speed, low power, lack of refresh, nearly unlimited endurance, and nonvolatility, and it becomes a very compelling alternative over the long term.

As opposed to the other MRAM-maker Everspin, Avalanche’s MRAM uses Continue reading

Cypress to Merge with Spansion

NOR flash and SRAM revenues are in decline, but MCUs are growing(Excerpted from an Objective Analysis Alert issued 1 December 2014.)

In a move touted as a merger of equals, Cypress will acquire Spansion in an all-stock transaction slated to close in the second quarter of 2015.  The purchase price is estimated at $1.6 billion.

Cypress points out that it is the leading producer of SRAMs, and that Spansion is the leading NOR flash provider.

One striking feature of this transaction is the Continue reading

Fundamentals of Memory – Free Online Course

Fundamentals of Memory Course - EE TimesSome time ago The Memory Guy was asked by Numonyx (later acquired by Micron) to put together an online course for EE Times on memory technologies, explaining how each one works and where it is used.

Although the course was very well received, I never posted a link to it on The Memory Guy blog.  This post is intended to correct that error.

The course runs 75 minutes and covers the basics of DRAM, non-volatile RAM, SRAM, NAND flash, NOR flash, mask ROM, and EEPROM.  It explains each technology’s advances in size, cost and performance, leading up to the development of Continue reading

Cheesecake and Floating Gates

Dr. Simon Sze, Co-Inventor of the Floating GateOne of the more fun aspects of last week’s Flash Memory Summit was the presentation of the Lifetime Achievement Award.  This is something that the show’s management has allowed me to do for the past four events.

This year’s award went to Dr. Simon Sze, who co-invented the floating gate transistor (the basis for all flash, EEPROM, and EPROM) at Bell Labs back in 1967.

Sze and his partner Dawon Kahng were finishing lunch in the company cafeteria with a cheesecake dessert.  The two discussed what would happen if a MOSFET was built with extra layers like the layers in the cake.  Their intent was to use semiconductors to replace Continue reading

Spansion’s Super-Fast HyperFlash NOR

Comparing Spansion's HyperFlash against the speed of alternative interfacesSpansion recently introduced a NOR flash that the company boasts is the: “World’s fastest NOR flash memory”.  Named HyperFlash, the chip taps into high-speed SPI interface, doubling its width and adding a differential clock to run at an I/O rates as high as 333MB/s.

In this post’s graphic (click to enlarge) Spansion compares the HyperFlash chip’s sustained read rate (right-hand column) to that of (from left to right) asynchronous parallel NOR, single-bit SPI, industry-standard DDR Quad SPI, and Spansion’s faster rendition of DDR Quad SPI, which Spansion tells us, until now, has been the fastest flash on the market.  The company points out that HyperFlash is five times the speed of industry-standard Continue reading

The Father of Flash Memory

Dr. Fujio Masuoka, the inventor of NAND and NOR flash memoryAt the Flash Memory Summit in August I had the honor of awarding Fujio Masuoka, the inventor of both NAND and NOR flash, the Flash Memory Summit Lifetime Achievement Award.  This award is given to the giants of the flash memory industry to acknowledge their contributions.

Dr. Masuoka first described NOR flash at the 1984 International Electron Device Meeting (IEDM) in San Francisco, and NAND flash at the same venue in 1987.  His paper “A new flash EEPROM cell using triple polysilicon technology” introduced a technology that is now used everywhere.

The award has also been given to Intel’s Flash team who brought the first commercial products to the market, and SanDisk co-founder Eli Harari, for devising a way to manufacture a floating gate.

David Schwaderer made a video of the presentation and posted it HERE.  Have a watch!

3D NAND: Benefits of Charge Traps over Floating Gates

Real California Cheese SealA prior post in this series (3D NAND: Making a Vertical String) discussed the difficulties of successfully manufacturing a charge trap flash bit.  Still, Spansion, and now other flash makers, have determined to take this route.  Why is that?

In Spansion’s case, a charge trap was a means of doubling the bit capacity of its products.  It was an inexpensive alternative to standard MLC flash.  To date this strategy has worked very well.

As mentioned in that earlier post, 3D NAND uses a charge trap because it’s extremely difficult to create features, like a floating gate, sideways – lithography works from the top down.  A charge trap, when used to replace a floating gate, doesn’t need to be patterned, since the Continue reading


Jim Handy Objective Analysis Memory Market Research +1 (408) 356-2549 Jim.Handy (at) Objective-Analysis.com

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