DRAM

When a Shortage Looms

DRAM Prices 1991-1997The Memory Guy has been getting calls lately asking how to tell that a shortage is developing.  My answer is always the same: It’s hard to tell.

One indicator is that spot prices which were below contract prices rise above contract prices.  This doesn’t happen for all components or densities of DRAM or NAND flash at the same time.  Some of these transitions are temporary as well.  It takes patience to see if it was a momentary change or if it was the onset of a shortage.

DRAM spot prices have generally been below contract prices since August 2014, but this month they raised above contract prices.  NAND flash spot prices also fell below contract prices in mid-2014 but today NAND’s spot price remains lower than contract prices.

Lead times represent another indicator.  If the lead time for a number of components increases then those chips are moving into a shortage.  Lead times have recently been rising for both NAND flash and DRAM.

A third indication occurs when suppliers start to Continue reading

Understanding Samsung’s DRAM CapEx Cut

Historical DRAM Wafer ProductionAccording to a Business Korea article Samsung announced, during a June 14 investor event, plans to reduce its DRAM capital spending and shift its focus to 3D NAND.

The Memory Guy sees this as an unsurprising move.  This post’s chart is an estimate of DRAM wafer production from 1991 through 2014.  There is a definite downtrend over the past few years.  The peak was reached in 2008 at an annual production of slightly below 15 million wafers, with a subsequent dip in 2009 thanks to the global financial collapse at the end of 2008.  After a slight recovery in 2010 the industry entered a period of steady decline.

The industry already has more than enough DRAM wafer capacity for the foreseeable future.

Why is this happening?  The answer is relatively simple: the gigabytes per wafer on a DRAM wafer are growing faster than the market’s demand for gigabytes.

Let’s dive into that in more detail.  The number of gigabytes on a DRAM wafer increases according Continue reading

Putting DRAM Prices in Perspective

DRAM Low Spot Pricing 2011-2016For almost two years there has been a lot of worry about DRAM spot prices.  This post’s graphic plots the lowest weekly spot price per gigabyte for the cheapest DRAM, regardless of density, on a semi-logarithmic scale.  (Remember that on a semi-logarithmic scale constant growth appears as a straight line.)

The downward-sloping red line on right side of the chart shows that DRAM prices have been sliding at a 45% annual rate since October 2014.  This has a lot of people worried for the health of the industry.

What most fail to remember, though, is that DRAM spot prices hit their lowest point twice in 2011, at $2.40 in August, and then $2.20 in November.  Today’s lowest DRAM spot prices have only recently dipped below the $2.52 point hit in October of 2014.

The black dotted line in the chart is intended to focus readers’ attention on DRAM costs, which decrease at a 30% average Continue reading

What is DRAM “Row Hammer”?

Barbara Aichinger, FuturePlus SystemsOne of those nasty little secrets about DRAM is that bits may get corrupted by simply reading the bits in a different part of the chip.  This has been given the name “Row Hammer” (or Rowhammer) because repeated accesses to a single one of the DRAM’s internal “rows” of bits can bleed charge off of the adjacent rows, causing bits to flip.  These repeated accesses are referred to as “hammering”.

Although this was once thought to be an issue only with DDR3 DRAMs, recent papers (listed on the DDR Detective) show that DDR4 also suffers from Row Hammer issues, even though DRAM makers took pains to prevent it.

One big champion of this phenomenon is Barbara Aichinger (pictured) of FuturePlus Systems, a test equipment maker that specializes in detecting row hammer issues.  The Memory Guy has had the pleasure of talking with her about this issue and learning first-hand the kind of difficulties it creates.

How does Row Hammer work?  It stems from the fact Continue reading

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!

Samsung’s Colossal 128GB DIMM

Samsung_128GB TSV RDIMMIn a November 25 press release Samsung introduced a 128GB DDR4 DIMM.  This is eight times the density of the largest broadly-available DIMM and rivals the full capacity of mainstream SSDs.

Naturally, the first question is: “How do they do that?”

To get all the chips into the DIMM format Samsung uses TSV interconnects on the DRAMs.  The module’s 36 DRAM packages each contain four 8Gb (1GB) chips, resulting in 144 DRAM chips squeezed into a standard DIMM format.  Each package also includes a data buffer chip, making the stack very closely resemble either the High-Bandwidth Memory (HBM) or the Hybrid Memory Cube (HMC).

Since these 36 packages (or worse, 144 DRAM chips) would overload the processor’s address bus, the DIMM uses an RDIMM protocol – the address and control pins are buffered on the DIMM before they reach the DRAM chips, cutting the processor bus loading by an order of magnitude or more.  RDIMMs are supported by certain server platforms.

The Memory Guy asked Samsung whether Continue reading

New Report: 3D XPoint Memory

3D XPoint Report Graphic

Objective Analysis has just introduced a new report that you might want to consider: A Close Look At The Micron/Intel 3D XPoint Memory.

The report covers the Intel-Micron 3D XPoint memory and includes Intel’s new Optane support products that are based on this technology.  The report explains the technology and its special manufacturing challenges.  It includes details of how 3D XPoint memory will be used, and provides an analysis of the benefits of its persistent nature.

Forecasts project how the market will develop and include optimistic and pessimistic forecast scenarios.  Particular attention has been paid to its impact upon the DRAM, SSD, and other markets.  Finally, the report analyzes different end-market segments to predict how this technology will impact each of them.

The Memory Guy, report author Jim Handy, will present the report’s findings during the Pre-Conference Primer of the Storage Network Industry Association (SNIA) Storage Developer Conference (SDC) this Sunday, September 20, at 2:00 PM, In Santa Clara, CA.

This breakthrough report is based on 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

Is Micron Being Acquired?

Tsinghua + Micron LogosThe following is an excerpt of an Objective Analysis Alert sent to our clients 7/13/15.

A July 13 Wall Street Journal article disclosed that China’s state-owned Tsinghua Unigroup has bid to buy Micron Technology for $21 a share or $23 billion, which would make this the largest-ever Chinese takeover of a U.S. company.

Objective Analysis has been telling our clients for the past few years that either China or India would create a new DRAM/NAND manufacturing company, especially since memory chip makers have enjoyed a long period of profits, and this usually motivates outsiders to invest in new DRAM makers.  We did not anticipate an acquisition.

Countries with heavy industry typically move into the semiconductor business during an extended upturn, and become DRAM suppliers since DRAM is an undifferentiated commodity.  Commodities sell almost solely on price and success is based on little more than manufacturing strength.  This is a business model that industrial economies understand.

In addition to Micron’s tangible assets, including Continue reading

How NAND Flash Can Reduce DRAM Requirements

Benchmarks show NAND advantage over DRAM in PCsIn a comment to a recent Memory Guy post I stated that NAND flash can reduce DRAM requirements, even in PCs.  Some readers have told me that they wonder how this could be, so I will write this post to explain.

Some years ago Objective Analysis noticed that clever server administrators were able to use SSDs to reduce their systems’ DRAM requirements.  Not only did this save them money, but it lowered power and cooling requirements as well.

Thinking that this might work on other kinds of computers, we commissioned a number of benchmarks to be performed on a PC.

These benchmarks found that after a system already has a certain minimum amount of DRAM, users can get a bigger performance boost by adding a dollar’s worth NAND flash than they can get by adding a dollar’s worth of DRAM.

In every case the minimum amount of DRAM was very small.

This benchmark data was compiled, written up, and explained in depth in the report: How PC NAND Will Undermine DRAM, which can Continue reading