The difference between ETLC and EMLC of solid-state hard disk

in 2015 years, TLC SSD has gradually become the market leading role, with the ultra-high cost performance of the SSDs launched a popular campaign. In the TLCSSD Gongchenglvede, many SSD companies began to play "EMLC", and TLC SSD Camp also appeared "ETLC" branch. So what exactly are these prefixes with "e" flash particles? Here's a chat about the difference between SSD ETLC and EMLC.

Solid State Drive

filtering process of flash particles

As early as the SLC NAND era, there were also flash particles called "ESLC". In the era of MLC and TLC Unified, the appearance of EMLC and ETLC appeared to be logical. Before we introduce them formally, let's review the filtering process for NAND flash particles:

Either SLC, MLC, or TLC, they are flash particles (also known as "Die") that are cut from the wafer, which can be made up of one or more circuits and eventually encapsulated into a NAND flash unit (Fig. 1). The more advanced the production process (for example, from 19nm to 15nm), the more flash particles are cut from each wafer (Figure 2), which means lower costs. The problem is, wafer. The production of silicon semiconductor integrated circuits has the concept of good product rate, not every wafer is perfectly qualified.

In the NAND flash particle field, we are accustomed to not pass any detection of the wafer (the cut out of flash particles) called "black", that is, the highest failure rate on the wafer. Unfortunately, these "black films" are rarely destroyed by the wafer factory, but through some channels spread out, often used in the cottage flash drive. Fortunately, few manufacturers will use it for SSDs, or rework after sales to drag down their own.

some flash particles experienced a wafer factory screening but did not pass the original fault detection, this kind of "defective piece" is often the second-line hard drive manufacturer procurement . At this point, the hard disk manufacturers will use their own factory detection of "defective piece" screening, the general detection of qualified flash particles are known as "white" (also known as good Die). Although the factory testing is not as strict as the original monitoring, but the "white piece" quality is still guaranteed.

If the flash particle successfully passed the wafer factory of the original screening and fault detection, at this time they will be known as the "original particles", and on the chip surface of the wafer plant (such as Toshiba, Spotlight, Heidelberg, flashing, Samsung, Intel) logo and model parameters and other information. If you take apart an SSD and find that the flash is not the mark of the wafer factory, but rather the logo of the SSD manufacturer's own (such as the Kinston logo), you can basically conclude that the SSD is using the "white piece" of the flash particle .

Unscrambling the meaning of "e" in ETLC and EMLC prefixes

Consumer-level market focus on speed, the enterprise-level market is focused on stability, this potential customer demand, but also let the wafer factory in the filtering of flash particles appeared in the branch.

In order to meet the requirements of the enterprise-level market, the wafer plant will be the best part of each wafer selected out of the unit, and in accordance with enterprise-class standards for its rigorous testing, all the data integrity and durability testing standards of the part of the flash particles, will be defined as "EMLC" or "ETLC." in other words, the prefix with "E", is the wafer factory special supply SSD manufacturers of the enterprise-class flash . These enterprise-class flash grains have more p/e (longer life) and better stability than normal MLC and TLC.

It is necessary to note that the "EMLC" and "ETLC" in the life of the advantages, also need to match the specified master chip and firmware algorithm . If there are SSD manufacturers to take EMLC/ETLC with the common master, it is not possible to achieve these enterprise-class flash should be high P/E value.

Speed can't lead "e" step

Unfortunately, in order to improve the P/E value, the "EMLC" and "ETLC" are more MLC/TLC than the time required to erase and program operations, which means they are not fast and match the SSD of the MLC/TLC Flash. To the Lite Rui T9 for example, this SSD uses Marvell 88ss9187 high-end control and Toshiba original EMLC granules, but the performance is not up to the expected height.

Thankfully, "EMLC" and "ETLC" are not synonymous with price increases. For example, a 256GB T9 (EMLC) only sell 499 yuan, and some Zhi Q300 (ETLC) less than 400 yuan, and the use of MLC and TLC product difference is very small. Therefore, if you value the data security extremely, the priority chooses with the Flash grain belt "E" the SSD to be correct (EMLC life is bigger than ETLC), but if you request to the SSD is the quicker the better, that does not have the E and is equipped with the high-end main control SSD to be more suitable for you