Tag Archives: Flash Memory

What is 3D MLC NAND Flash Memory?

To unleash performance fit for the next generation of computers, Transcend has released its MTE850 M.2 Solid State Device (SSD), based on 3D MLC NAND flash memory. The device utilizes the PCI Express Gen3 x4 interface and supports the latest NVMe standard. According to Transcend, this SSD targets high-end applications such as gaming, digital audio and video production, and multiple uses in the enterprise. Typically, such applications demand constant processing of heavy workloads, while not willing to stand any system slowdowns or lags of any kind. Transcend claims the MTE850 M.2 SSD will offer users high-speed transfers and unmatched reliability.

High Speeds for High-End Applications

As the above SSD uses the PCIe Gen3 x4 interface and follows NVMe 1.2 standard, it transmits and receives data on four lanes simultaneously. This results in the SSD working at the blazing speeds of up to 1100 MBps while writing, and up to 2500 MBps while reading.

Why the PCIe Interface

Presently, the most popular method of connecting a host computer to an SSD is through SATA or Serial ATA interface. However, PCIe uses one transmit and one receive serial interfaces in each of the four lanes, the PCIe interface is much faster than SATA is, and it is able to fulfill new performance requirements in better ways.

Why the NVMe Standard

The growing needs of enterprise and client applications demands better performance vectors than the Advanced Host Controller Interface (AHCI) can provide. The NVM Express (NVMe) fulfills this enhanced host controller interface standard, which also calls for low latency, increased IOPS, and scalable bandwidth.

What is 3-D Expansion?

Existing planar NAND memory chips are arranged in the form of flat two-dimensional arrays. In contrast, 3-D NAND flash has memory cells stacked in the vertical direction as well as in multiple layers. This breaks through the density limitations of the existing 2-D planar NAND, with the 3-D NAND offering a far greater level of performance and endurance.

With Better Endurance Comes Higher Reliability

To help keep data secure, Transcend has engineered their MTE850 M.2 SSD with a RAID engine (a type of data storage virtualization technology) and Low-Density Parity Check (LDPC) coding, along with an Elliptical Curve Cryptography (ECC) algorithm. Additionally, Transcend manufactures their SSDs with top-tier MLC NAND flash chips and provides them with engineered dynamic thermal throttling mechanism. This way, Transcend ensures the MTE850 delivers superior stability and endurance befitting for high-end applications.

SSD Scope Software

Users can download the SSD Scope software application free of charge from the Transcend site. The application helps to monitor the health of the running SSD using SMART technology and allows the user to enable the TRIM command to obtain optimum write speeds. Using the application also keeps the firmware of the SSD up-to-date, and helps in migrating data from the original drive to the new SSD with only a few clicks.

With certificates from CE, FCC, and BSMI the #-D MLC NAND flash memory based  MTE850 M.2 SSD from Transcend works on 3.3 VDC ±5%, operating within 0 and 70°C. With mechanical dimensions of 80x22x3.58 mm, the SSD weighs only 8 grams.

Replacement for Flash Memory

Today flash memories or thumb drives are commonly used as devices that store information even without power—nonvolatile memory. However, physicists and researchers are of the opinion that flash memory is nearing the end of its size and performance limits. Therefore, the computer industry is in search of a replacement for flash memory. For instance, the National Institute of Technology (NIST) conducted research is suggesting resistive random access memory (RRAM) as a worthy successor for the next generation of nonvolatile computer memory.

RRAM has several advantages over flash. Potentially faster and less energy hungry than flash, it is also able to pack in far more information within a given space. This is because its switches are tiny enough to store a terabyte within a space the size of a postage stamp. So far, technical hurdles have been preventing RRAM from being broadly commercialized.

One such hurdle physicists and researchers are facing is the RRAM variability. To be a practical memory, a switch needs to have two distinct states—representing a digital one or zero, and a predictable way of flipping from one state to the other. Conventional memory switches behave reliably when they receive an electrical pulse and switch states predictably. However, RRAM switches are still not so reliable, and their behavior is unpredictable.

Inside a RRAM switch, an electrical pulse flips it on or off by moving oxygen atoms around, thereby creating or breaking a conductive path through an insulating oxide. When the pulses are short and energetic, they are more effective in moving ions by the right amount for creating distinct on/off states. This potentially minimizes the longstanding problem of overlapping states largely keeping the RRAM in the R&D stage.

According to a guest researcher at NIST, David Nminibapiel, RRAMs are as yet highly unpredictable. The amount of energy required to flip a switch may not be adequate to do the same the next time around. Applying too much energy may cause it to overshoot, and may worsen the variability problem. In addition, even with a successful flip, the two states could overlap, and that makes it unclear whether the switch is actually storing a zero or a one.

Although this randomness takes away from the advantages of the technology, the researcher team at NIST has discovered a potential solution. They have found the energy delivered to the switch may be controlled with several short pulses rather than using one long pulse.

Typically, conventional memory chips work with relatively strong pulses lasting about a nanosecond. However, the NIST team found less energetic pulses of about 100 picoseconds, which were only a tenth of the conventional pulses, worked better with RRAM.  Sending a few of these gentler signals, the team noticed, was more useful not only for flipping the RRAM switches predictably, but also for exploring the behavior of the switches.

That led the team to conclude these shorter signals reduce the variability. Although the issue does not go away totally, but tapping the switch several times with the lighter pulses makes the switch flip gradually, while allowing checking to verify whether the switch did flip successfully.

What is 3D Flash Memory?

Slowly, but steadily, the memory market is veering away from magnetic disc storage systems to solid-state drives or SSDs. Not only are prices falling fast, manufacturers are producing SSDs with improved technologies, leading to denser memories, higher reliability and lower costs. For example, Samsung has recently announced SSD and systems designs that will drive their new 3-D NAND into mass markets.

Samsung’s latest SSDs are the 850 EVO series. According to Jim Eliot, a marketing executive for Samsung, these are 48-layer, 256 Gbit 3-D NAND cells, with 3-bits per cell. The new chips show more than 50% better power efficiency and twice the performance when compared to the 32-layer chips Samsung is now producing. In the future, Samsung is targeting Tbit-class chips made with more than 100 layers.

On a similar note, an engineer with SK Hynix says that by the third quarter, the company will start production of 3-D NAND chips with more than 30 layers. By 2019, SK Hynix will be making chips containing more than 190 layers.

At present, 3-D NAND production is still low in yield and the cost of production is higher than for producing traditional planar flash chips. However, these dense chips bring promises of several generations of continuing decreases in costs and improvements in the performance of flash. According to analysts and vendors, it might take another year or so before the new technology is ready for use in the mainstream.

Samsung was the first to announce 3-D NAND production, with rivals catching up fast. Toshiba has already announced its intentions of producing 256 Gbit 3-D NAND chips in September. These will also have 48 layers and 3-bits per cell.

According to Jim Handy, an analyst at the Objective Analysis, Los Gatos, California, sales of the 3-D NAND will not pick up before 2017. With Samsung shipping its V-NAND SSDs at a loss, they are gearing up to put the 48-layer devices in volume production. This will enable them to beat the cost of traditional flash.

The reason is not hard to find. Wafers of 3-D chips with 32-layers cost 70% higher than wafers for traditional flash. On the other hand, wafers for 48-layer versions cost only 5-10% higher, but have 50% more layers. Therefore, although the 48-layer chips tend to start with a 50% yield, they will easily approach the planar flash yield levels with a year or so.

According to expert analysts, it takes a couple of years for any new technology to mature. Therefore, the prediction that 3D NAND will reach a majority of flash bit sales only after 2018.

The number of 3D layers providing an optimal product is still under experimentation. Also, included is the development of a new class of controllers and firmware for managing the larger block sizes. Vendors are still exploring other unique characteristics of these 3D chips.

For example, Samsung has designed controllers and firmware that addresses the unique requirements of 3-D NAND and is selling its chips only in SSD form. According to the head of Samsung’s Memory Solutions Lab, Bob Brennan, SSDs provide higher profit margins as compared to merchant chips, and are the fastest way to market.