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RAM in an SSD context

RAM based SSDs
memory channel SSDs
MemCon 2013 - papers
the Memory Guy's DRAM blog
RAM Cache Ratios in flash SSDs
DRAM spot market prices - daily
A brief history of database RAM storage
memory news - from ElectronicDesign.com
RAM SSDs versus Flash SSDs - which is Best?
The World's First Commercial DRAM - Intel 1103
3rd Party RAM - Your Legal Rights to Server Warranties
Everything You Wanted to Know about SOC Memory (pdf)
What Every Programmer Should Know About Memory (pdf)
Samsung in volume production of 20nm DDR3 RAM

Editor:- March 11, 2014 - 40 years ago in the early days of MOS LSI - whenever semiconductor companies like Intel wanted to characterize a new semiconductor production process and establish the "safe" design rules for manufacturability at ever smaller chip geometries (aka "shrink") the circuit and product of choice for the fab architects was memory - even if the eventual product for the wafer fab was going to be a microprocessor.

More recently - in the past few years - if you've been looking at all those "nm" (nanometer) numbers in the news stories about IT related chips you can hardly fail to have noticed that it's been the flash memory devices which have been at the leading edge of the numbers. And when looking at production devices - flash has been about 2 years in advance of DRAM and server CPUs.

You've often heard on these pages that it's only by breaking the safe design rules used in preceding generations that interesting new SSDs come to market.

And a big part of the to-do list for any SSD controllers is to cope with a predictable scale and style of expected memory defects and virtualize them away - creating a usable base level storage device.

Fitting in line with this trend - Samsung today announced it's using 20nm technology in the production of new 4Gb DDR3 DRAM.

As comparison points:
  • Samsung was doing volume production of 10nm flash (used in consumer eMMC SSDs for mobile phones) in November 2012.
The way this pattern has been going in recent years is that the first volume uses of new silicon geometries go into consumer markets - where if there's a data upset - you can see something wrong happening (blue screen or freeze) turn the power off and try things again. After several quarters of doing this - the chip bakeries have finely tuned their recipes and are ready to guarantee a less crumbly dough mixture for use in the enterprise.

But if these concepts are new to you - it's not worthwhile memorizing them. Because 3D nand flash changes the priority of future enhancements towards a preference for building upwards in more layers instead of merely thinning sideways.


Virtium launches 32GB ULP RAM with industrial screening

Editor:- February 26, 2014 - Virtium today introduced 2 new low profile 16GB and 32GB DDR3 RAM modules in these form factors - ULP (Ultra-Low Profile) - 0.70" high and VLP (Very-Low Profile) - 0.738" high - for use in dense embedded servers which need industrial temperature operation in these form factors.

Editor's comments:- as with industrial SSDs - one of the differences in industrial memory is the screening process. Virtium's memory blog says that using 24 hour TDBI (Test During Burn-In) chambers can reduce early failures up to 90%.

See also:-
how bad parity lost Sun its reputation for SPARC reliability
general principles of improving electronic reliability by screening
An Empirical Study of Memory Hardware Errors in a Server Farm (pdf)


Hybrid Memory Cube gets x2 speedup

Editor:- February 25, 2014 - Although the market for Hybrid Memory Cube compatible RAM has barely begun - a new Gen2 specification was announced today which doubles the fastest short-reach data performance (previously 15Gb/s) upto 30Gb/s. See also:- ORGs, RAM DIMM compatible SSDs


the Top SSD Companies in Q4 2013

Editor:- January 31, 2014 - StorageSearch.com today published the 27th quarterly edition of the Top SSD Companies - based on market metrics in Q4 2013.


what changed in SSD year 2013?

Editor:- December 9, 2013 - The important ideas in the SSD market seem to change every year. To avoid making bad decisions you not only have to learn new SSD ideas but you also need to identify which old SSD ideas to forget. That's the theme of a new article on StorageSearch.com - what changed in SSD year 2013?.


Micron samples 2GB HMC

Editor:- September 25, 2013 - Micron today announced it's sampling the company's first implementation of the Hybrid Memory Cube (high density chip stacking architecture standard) which was launched in October 2011). Micron's SR (short reach) HMC provides 2GB DRAM in a BGA - with upto 160 GB/s bandwidth.


More smoke than fire at SK Hynix memory plant

Editor:- September 5, 2013 - Yesterday there was widely reported speculation about the possible market impact of a fire at an SK Hynix memory plant - which makes upto 15% of the world's DRAM chips.

In a clarification statement reported by Reuters the company said there was no material damaage to the clean rooms and SK Hynix anticipated that supply volumes would not be materially affected.

Editor's comments:- 3 weeks ago it was announced that 16nm flash from SK Hynix is the main memory building block in Skyera's 1U half petabyte skyEagle SSD rack.


DRAM technology won't advance soon - says Micron

Editor:- August 20, 2013 - In recent years the SSD market has become nearly 100% flash (and nv memory) focused - with little or no mention of DRAM based SSDs. The reason is that nearly every company whose product line used to be mainstream RAM SSD - has pulled out of that market or discontinued enhancements to those products. Flash SSDs are more economic and easier to sell.

It doesn't mean to say that the role of DRAM in SSD systems has entirely disappeared. It still appears as a cache or tier in many flash SSD arrays and the existence of some small percentage of DRAM is assumed in SSD caching software and also in (flash based) memory channel SSDs.

Micron sent out a useful signal of where its own DRAM roadmap is going in an article yesterday in EETimes - which reports an interview with Micron's president Mark Adams who said - "There will be no new greenfield DRAM fabs for the foreseeable future. We are hitting something of a lithography wall in DRAM where shrinks are getting tougher and gains are not as attractive, so people are not as financially motivated to invest in new fabs. Also we see planar DRAM advances will end in the next 3 to 5 years, so you probably cannot get ROI in a new planar fab." ...read the article


SMART samples ULLtraDIMM SSDs

Editor:- August 8, 2013 - SMART Storage Systems today announced it has begun sampling the first memory channel SSDs compatible with the interface and reference architecture created by Diablo Technologies.

SMART's first generation enterprise ULLtraDIMM SSD (ULL = ultra-low latency) can be deployed via any existing DIMM slot and provides 200GB or 400GB of enterprise class flash SSD memory with upto 1GB/s and 760MB/s of sustained read/write performance, with 5 microseconds write latency. Throughput, IOPS and memory capacity all scale with the number of ULLtraDIMM deployed in each server.

ultra low latency memory channel SSD

Editor's comments:- With the current design -only one DIMM slot in each server has to be reserved for conventional DRAM. Apart from that constraint any DIMM slot can be used for either flash or DRAM as deemed necessary for the application.

For more about the potential of this technology, the thinking behind it and the competitive landscape relative to PCIe SSDs etc see my earlier articles on the Memory Channel SSDs page.


Hybrid Memory Cube spec ready for chip designers

Editor:- April 3, 2013 - back in October 2011 - I reported on this page the formation of a new industry ORG - the Hybrid Memory Cube Consortium - which could have an impact on future SSD packaging densities.

It takes a while to get these things going - but according to a press release this week by one of the founding companies - Micron - the 100 plus companies which are collaborating in this enterprise have agreed on an interface specification (pdf).

A key feature of the new multiplane memory architecture is that distributed memory controllers in an HMC module will handle the data I/O packet requests for the bunch of stacked memory chips in its own vault. This is similar to the distributed intelligent data mover concept which is already used in all proprietary big architecture SSD controller designs - because it's the only way you can get good aggregated global system performance while also dealing with low level local memory management issues at low latency.

As with earlier generations of remote distributed memory interfaces - such as InfiniBand - HMC is designed to optimize the request of small packets - which in the case of HMC is 16 to 128 bytes of data.

With today's semiconductor speeds - accessing the data in those distributed memory chips within the same HMC module presents similar technical problems to distributed memory cards in traditional computer designs - because traversing inches of physical space at high speed is as difficult as moving data across tens of feet at slower speeds.

HMC has been born as a DRAM technology - but don't ignore it - just for that reason. (Or because the data packet sizes are small compared to the block sizes in nand flash.) If and when these HMC packaging ideas result in viable products - the ideas and methodologies will spill into SSDs too -regardless of what the underlying memories used in SSDs may be at that time.

It's all about speed and scalability. According to the HMC faqs page - A single (1st generation) HMC unit can provide more than 15x the bandwidth of a DDR3 module. See also:- SSD interface glue chips.


Micron sources power holdup technology for NVDIMMs

Editor:- November 14, 2012 - Micron has signed an agreement with AgigA Tech to collaborate to develop and offer nonvolatile DIMM (NVDIMM) products using AgigA's PowerGEM (sudden power loss controller and holdup modules).


NEC Hitachi Memory dream ends in Elpida bankruptcy

Editor:- February 27, 2012 - Elpida today announced it is reorganizing under the code of the bankruptcy laws in Japan.

Editor's comments:- The company's press release (pdf) relates a detailed history of problems starting in 2007 with the credit crunch, over capacity, falling RAM prices, increasing strength of Yen etc. The company - Japan's biggest surviving RAM maker - started out as NEC Hitachi Memory in 1999 and changed its name to Elpida in 2000.

Elpida never got into the SSD market. Now it looks like it never will.

A report in the New York Times says - "Elpida's bankruptcy filing is the biggest ever by a Japan-based manufacturer..."


Viking ships nv 8GB DDR3 DIMM

Editor:- October 18, 2011 - Viking Modular Solutions said it is shipping an extension of their nv module range.

The DDR3 ArxCis-NV plugs into standard RAM sockets and provides 2GB to 8GB RAM which is backed up to SLC flash in the event of a power failure - while the memory power is held up by an optional external 25F supercap pack. Viking says these new memory modules can eliminate the need for battery backup units in servers and the maintenance logistics associated with maintaining them. They are specified as being maintenance free for "5 years @ 60°C".

Editor's comments:- will these new modules replace batteries in RAM SSDs? - I doubt it - because of scalability issues - like managing a spiderweb of 100+ dangly bits of wire when you have a terabyte of RAM. Having said that - there are many applications which only use a small number of memory chips which could benefit from such a product.


Hybrid Memory Cube will enable Petabyte SSDs

Editor:- October 7, 2011 - Samsung and Micron this week launched an new industry initiative - the Hybrid Memory Cube Consortium - which will standardize a new module architecture for memory chips - enabling greater density, faster bandwidth and lower power.

"HMC is unlike anything currently on the radar," said Robert Feurle, Micron's VP for DRAM Marketing. "HMC brings a new level of capability to memory that provides exponential performance and efficiency gains that will redefine the future of memory."

Editor's comments:- HMC may enable SSD designers to pack 10x more RAM capacity into the same space with upto 15x the bandwidth, while using 1/3 the power due to its integrated power management plane.

The same technology will enable denser flash SSDs too - if flash is still around in 3 years' time and hasn't been sucked into the obsolete market slime pit by the lurking nv demons which have been shadowing flash for the past 10 years and been waiting for each "next generation" to stumble and be the last.

The power management architecture integrated in HMC and the density scaling it allows for packing memory chips (without heat build-up) are key technology enablers which were listed as some of the problems the SSD industry needed to solve in my 2010 article - this way to the Petabyte SSD.
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"Across the whole enterprise - a single petabyte of SSD with new software could replace 10 to 50 petabytes of raw legacy HDD storage and still enable all the apps to run much faster while being hosted on a shrunken population of SSD enhanced servers."
meet Ken and the enterprise SSD software event horizon
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Partial list of past and present RAM manufacturers - mentioned in storage news / history.

A-DATA, Adtec , AGIGA Tech , Alliance Semiconductor, ANACAPA, Apacer Memory America, ATP Electronics, Austin Semiconductor, Avant North America, Cambex , Century Microelectronics, Corsair Memory, Crucial Technology, Cypress Semiconductor, Dane-Elec Memory, Dataram, EDGE Tech, Elpida Memory, Fairchild Semiconductor, Gigaram, Hynix Semiconductor, IBM Microelectronics, Inotera Memories, Kentron Technologies, Kingston Technology, MemoryTen, Micro Memory, Micro Memory Bank, Micron Technology, Mosel Vitelic, Mushkin, MoSys, Nanya Technology, NEC, Netlist, Patriot Memory, Piiceon, PNY Technologies, Qimonda, Ramaxel Technology , Ramtron , Renesas Technology, Rocky Mountain Ram, Samsung Electronics, Silicon Mountain Memory, Silicon Power , SimpleTech, SMART Modular Technologies, Southland Micro Systems, Spansion, STMicroelectronics, Swissbit, TopRam, Toshiba, Transcend Information, TwinMOS Technologies, Unigen, Viking Modular Solutions, VisionTek, White Electronic Designs, Winbond Electronics , Z Tech International.
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RAM Despite the cost - Megabyte found that RAM gave him the fastest access to what he was seeking.
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are you ready to adapt to new ways of thinking about DRAM?
Editor:- April 2, 2014 - DRAM doesn't have to be as boringly predictable in design as you think.

If adding intelligence to flash makes better SSDs - then how about revisiting all the assumptions in DRAM too?

Some researchers have been thinking about this topic for years.

And if only some of their ideas prove workable - there may be enough critical mass to create a new type of enterprise DRAM - which is an intelligent storage component.

DRAM inherently costs a lot per bit - so why not demand more QoS benefits than you can expect from a "passive slave"* type of DRAM whose DNA origins lie in 1970s Intel memory circuit design layouts which were done by hand?

These ideas are brought together in the new home page blog on StorageSearch.com ...read the article

* - This "passive slave" description of classic DRAM architecture - which I really like - comes from a paper by Onur Mutlu - which is discussed in my new blog.


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re RAM - by Zsolt Kerekes, editor
RAM - Random Access Memory - is the fastest type of storage.

It's implemented by silicon chips which can contain upto thousands of millions of storage bits (gigabits) connected in a randomly accessible array.

The "random access" part of the RAM name was to differentiate RAM from earlier types of memory (more than 30 years ago) which were stored in blocks (or rings) which meant that reading or writing to selected memory bits involved processing the contents of the block through a shift register. RAM was easier to write software for and faster.

RAM has equal read and write access times (unlike flash memory). Other significant differences to flash are:-
  • the data stored in a RAM is only maintained while the device is powered up (is volatile)
  • RAM doesn't suffer from write wear-out (endurance)
  • RAM is typically more expensive than flash for the same capacity, and typically uses more electrical power. The exception is smaller capacity memories inside a chip where the complexity of managing flash memory incurs more overhead than the much simpler overheads in RAM.
RAM products have different designs and are optimized for various markets (such as servers, notebooks and graphics cache) based on their speed, cost, interface and capacity.

The earliest SSDs used battery backed RAMS. RAM SSDs still exist in 2011 and are economic in some high performance applications and sometimes use flash as the internal backup medium (instead of hard disks) to enable fast boot.

RAM is susceptible to random data corruption by radioactive particles which occur naturally in many locations - and which also strike the earth from cosmic rays. That's why ever since the earliest high density DRAM memory systems were designed in the 1970s - it has been necessary to integrate various types of error correction - ranging from simple parity checks, and error correcting codes right up to active data monitoring and healing in high capacity RAM SSDs which is implemented by dedicated RAM controllers.


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image for ULLtraDIMM IBM article


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"...The RAM market faces disruptive challenges from SSDs - just as hard disks have done. At some time during the next 5 years - most of the world's new memory will be deployed inside an SSD or an SSD controlled loop. Owning an SSD brand will be as important in the new market for memory makers as getting designed into tier 1 server slots was in the past. Commercial RAM makers will have to re-engineer themselves into SSD companies - or risk lower profit margins from selling to SSD brands at spot market prices from outside the SSD box."
...Editor:- talking to a market strategist in one of the world's biggest seminconductor companies in June 2011.



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"I'm often asked if I could foresee how important (DRAM) would become," said Robert Dennard (the inventor of DRAM) on receiving a lifetime achievement award in 2005.

"I knew it was going to be a big thing, but I didn't know it would grow to have the wide impact that it has today." ...read the article



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