Samsung building cheaper SSDs with triple level flash memory
Cheaper technology could cut cost to consumers
By Stephen Lawson | Published: 10:34, 12 April 2012
A new type of NAND flash storage for consumer electronics that can store data more densely might lower the cost of devices such as tablets and thin "ultrabook" laptops, according to Samsung.
Most manufacturers have not yet started using the so-called TLC (triple-level cell) chips in devices, but as they grow more comfortable with the longevity of flash, they may adopt it, said Ryan Smith, Samsung senior manager of SSD product marketing. If TLC is robust enough to handle the average user's daily activity on a device over the time they would typically own it, consumers could benefit from cheaper hardware, Smith said.
Flash storage works by applying a high-voltage pulse to modify the charges on individual cells within a chip. SLC or single-level cell flash, used in enterprise storage equipment, applies only one charge to a whole cell, to store one bit. MLC (multilevel cell) can apply a higher or a lower charge and store two bits. TLC takes that to three bits.
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TLC lets flash makers get more chips of a given capacity out of one wafer, which is why it's less expensive, according to Forward Insights analyst Gregory Wong. On the other hand, as the number of charges per cell goes up, so do the number of errors, and the number of times a user can reliably write data to the storage goes down, he added. Performance is also lower on TLC than on the other types of flash, though all are faster than hard disk drives, Wong said.
Samsung acknowledges the longevity and error issues, which can be partly solved through error correction and digital signal processing. But the company believes that MLC flash, the kind used in most laptops and tablets today, may be overkill for the needs of the average user. If TLC can keep working for however long a user keeps a machine, that machine may cost the consumer less, he said.
It's up to device makers to decide whether TLC is good enough, Smith added. Whether it can go the distance is a complicated question. A typical rule of thumb in the industry for laptop use is writing 20GB of data per day to the device, over a period of perhaps three years, he said. That includes files created or downloaded as well as temporarily cached web pages and other items.
Using that standard, "TLC is on the borderline unless some special error correction or signal processing gives you some margin," Wong said. But the 20GB rule may be more than the average user needs, he added. With tablets in particular, consumers tend not to create and store much content, though tablets typically have less flash capacity and therefore fewer cells to work with over the life of the product, Wong said.
TLC is already used in removable storage devices, such as cards and USB drives, and some manufacturers have used it in products such as e-readers and personal navigation devices, particularly on the low end of the market, Wong said. But it might make the leap to mainstream gear at some point, he said.
"If it can provide a very attractive cost savings, then you can expect that some of them will probably dabble in it," Wong said.
Also on Tuesday, Smith acknowledged the diminishing returns due from shrinking NAND flash to tighter design geometries. Samsung and other manufacturers make flash chips at about 20 nanometers today, but that is expected to shrink over the next few years. Studies have shown that smaller geometries will slow flash down and cause more errors, though it is expected to remain faster than hard disk drives.
"The physics there are becoming challenging for protecting the integrity of the data," Smith said. To counter that, flash vendors are working on better error correction technologies, including digital signal processors, he said. Demand for that kind of capability drove Apple's recent acquisition of Anobit, Smith said. "2012 is all about that technology. People are trying to differentiate themselves on that."