What is a 3D NAND?

Applied Materials' Explanation of 3D NAND. A series of diagrams shows: 1) a horizontal NAND string, 2) That string being split into two, 3) The string being folded over at the split, and 4) the folded string being tilted on its end.(The following is an update of a post that originally ran 25 October 2013.  It was republished in 2024 as a part of a series to honor the 3D NAND inventors who have received the 2024 FMS Lifetime Achievement Award.)


In the prior post we discussed the need to go vertically into the body of the die, since NAND flash can not Continue reading “What is a 3D NAND?”

Announcing Our New CXL Report

Sketch of a CXL 3.0 fabric. There are four switches in the middle of the diagram on the top left and right and the bottom left and right. Each switch is connected to all of the others via CXL ISL Links, which are represented by a simple straight line between each one. Each switch is also connected to two hosts through two CXL Links, so there are eight hosts in the sketch. The two right-side switches are also connected to two CXL memory modules, which connect to the CXL link to the switch through a yellow box called "CXL MC" representing the CXL Memory Controller and to a red box marked "Mem" representing the memory chips.The Memory Guy is pleased to announce general availability of a new Objective Analysis Detailed Report: CXL Looks for the Perfect Home.

Since Compute Express Link (CXL) is so important to members of the DRAM market and the hyperscale computing community, the report focuses on those sectors, but it offers Continue reading “Announcing Our New CXL Report”

Why Do We Need 3D NAND?

NAND Flash Capped Gate Structure(The following is an update of a post that originally ran 18 October 2013.  It was republished in 2024 as a part of a series to honor the 3D NAND inventors who have received the 2024 FMS Lifetime Achievement Award.)


A memory chip of a certain area costs about the same amount to produce, no matter how many bits it holds. Naturally, the more bits you can cram onto this chip, the cheaper the price per bit will be. Low cost is of the utmost Continue reading “Why Do We Need 3D NAND?”

FMS – New Focus and a Heavy AI and CXL presence

Last week’s FMS conference, originally the Flash Memory Summit, but now the Future of Memory and Storage, saw a strong return of the show’s original excitement and attendance, with numerous presentations on key new technologies, largely AI and CXL, and crowds similar to those before the pandemic.  FMS is held in early August every year in Santa Clara, California.

The new name is meant to match the show’s content better than Continue reading “FMS – New Focus and a Heavy AI and CXL presence”

What is 3D NAND? Why do we need it? How do they make it?

3D NANDBack in 2013, when Samsung announced its V-NAND, the first production 3D NAND, The Memory Guy blog carried a series of posts to explain the new technology and the reason it was so necessary.

Now that the inventors of this technology have been honored with the FMS Lifetime Achievement Award, I decided that it was time to refresh that series of blog posts.  Once a week for the next nine weeks I will be reissuing a post in this series.  I hope that these will Continue reading “What is 3D NAND? Why do we need it? How do they make it?”

3D NAND Team to Receive FMS Lifetime Achievement Award

3D-drawn simplified image of 3D NAND.FMS (formerly the Flash Memory Summit) announced on July 24 that a research team from Kioxia will receive the award for inventing 3D NAND flash at FMS: the Future of Memory and Storage, on August 6 in Santa Clara, California.  We hope to see you there as the award is being presented to a member of that team.

The team has five Continue reading “3D NAND Team to Receive FMS Lifetime Achievement Award”

Finally! A Real Virtual Memory Chip

A big red letter X over a box marked MMUAt long last a chip has been embodied to simplify the use of virtual memory, a computing architecture that has been in use since the 1960s. The Memory Guy was given a sneak peek at this new approach by no other than Olly Mugwump, a highly-respected computer architect and longstanding member and fellow of several important technical societies.  The new design promises to accelerate memory accesses while Continue reading “Finally! A Real Virtual Memory Chip”

What is “Stranded Memory?”

Cartoon of a tiny island of sand with a single palm tree and a DIMM. "Help" is written in the sand.CXL has been embraced by hyperscale data center managers as a means of solving the problem of “Stranded Memory.”  If you don’t know what stranded memory is, then this post is intended to help you to understand.  It’s based on a few slides from a presentation that IEEE President Tom Coughlin and The Memory Guy made at the Storage Networking Industry Association (SNIA) CMS Summit in April 2023.  SNIA has posted a video of the entire Continue reading “What is “Stranded Memory?””

Processing-In-Memory, 1960s-Style

Famous photo of Apollo 11's Buzz Aldrin on the moon.There’s a surge of interest these days in Processing in Memory or PIM.  Some call it “Compute in Memory.”  Either way, it often involves adding small amounts of logic to a memory chip to allow it to offload tasks from the CPU.

There are various reasons to do this.  The most important is that PIM frees the CPU to do other chores.  PIM also can reduce Continue reading “Processing-In-Memory, 1960s-Style”

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