Shulou(Shulou.com)05/31 Report--

Modern fever-grade solid state drives (SSD) provide unparalleled performance. However, they tend to generate a lot of heat, which may damage the performance and data of NAND flash chips. Phison said that as drives become more advanced, they also become hotter, so it is expected that the high-end PCIe Gen 5 SSD will need to use fans for active cooling (perhaps, as shown in the figure above). At the same time, the company says it is trying to reduce the heat of its controller because applications such as laptops or compact desktops cannot accommodate large coolers.

"We are doing a lot to keep SSD power within a reasonable range," Sebastien Jean, Groupon's chief technology officer, said in a recent interview with MSI Insider and StorageReview. "but what is certain is that SSD will get hotter, just as CPU and GPU got hotter in the 1990s. As we move to Gen5 and Gen6, we may need to consider active cooling."

Higher capacity leads to complex controllers

To gain capacity, 3D NAND flash memory increases the number of layers or the number of charge levels it can store in a single cell. However, the increase in the number of layers usually reduces the physical size of the battery, which fundamentally affects its ability to store charge reliably (alleviated by the use of new materials). In contrast, the shift from level 3 to level 4 cell architecture fundamentally reduces the number of programming / erasure cycles that a unit can withstand. Due to the coexistence of two methods to increase the recording density of 3D NAND, this will eventually lead to a decline in the signal quality generated by these NAND units. Therefore, the SSD controller must adopt more complex error correction methods to process these signals.

These complex methods have low-density parity-check (LDPC) code algorithms. These tend to be computationally intensive, so in recent years, SSD controllers have gained complexity and computing power. Without these algorithms, we have nowhere to go, and the controller will continue to become more capable and hotter.

SSD controller developers like Groupon have adopted more sophisticated technology in their state-of-the-art controllers. Nonetheless, adoption seems to be slower than complexity increases, which is why SSD controllers for fever-level and enterprise / server applications continue to gain hot design power (TDP).

Temperature: controller is 120 °C, but NAND IC is only 70 °C

Enthusiastic readers know that modern CPU and GPU can withstand extreme temperatures of about 100C or more (although it runs reliably within the specification range at the cost of silicon degradation, it loses its overclocking capability). The same is true of SSD controllers. According to Groupon, these products are produced by contract manufacturers such as TSMC and can withstand temperatures of up to 120 degrees Celsius.

The problem, however, is that the controller will heat 3D NAND IC at 120C, and its reliability will be greatly reduced at 75C and above. Therefore, in order to prevent data loss, the controller usually begins to throttle at high temperature, thus affecting performance.

"3D NAND memory can handle any temperature from 0 °C (32 °F) to 70 °C to 85 °C (158 °F to 185 °F), depending on the level of NAND," Jean said. "as the temperature increases, the data retention rate in NAND decreases. [.] If most of your data is hot and you read it coldly, then you have a huge cross-temperature fluctuation. SSD can handle this problem and translate it into more error correction. Therefore, the maximum throughput is reduced. SSD is between 25 °C and 50 °C (77 °F to 122 °F). "

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