JEDEC has released the UFS 3.1 specification (also known as the JESD220E), which adds features related to performance, power, cost reduction, and reliability to the standard. These new features and features promise to improve real-world device performance, minimize power consumption, potentially reduce the cost of high-capacity storage devices, and improve the user experience.
UFS 3.1 compliant devices continue to use MIPI’s M-PHY 4.1 physical layer and 8b/10b line encoding, which is based on the UniPro 1.8 protocol’s interconnect layer (IL) at hS-G4 (11.6 Gbps) per channel. At the same time, the new version of the specification supports three new features: write enhancement, deep sleep, and performance limitation notifications. In addition, JEDEC has published technical specifications for host performance improvement. Modern SSDs already support all of these features, so the UFS 3.1 specification and HP make UFS storage devices functionally closer to SSDs.
Write Booster is designed to increase write speed by using pseudo-SLC caches, as the name suggests. Similar technology is already used by SSDs and various NVMe-powered micro-storage devices, such as those used in Apple’s iPhone/iPad. Similarly, the SD 6.0 standard supports caching to meet write performance objectives.
The second important new feature of UFS 3.1 technology is Deep Sleep, a new low-power state for inexpensive UFS devices that use the same regulator for storage and other functions. Another new feature is performance limit notification, which allows UFS devices to notify hosts about performance limitations when they overheat. Ultimately, avoiding throttle means more stable performance.
There is also the Host Performance Booster, which caches UFS device logic-to-physical (LTP) address mapping in the system’s DRAM to improve performance. Mobile applications use a large number of random reads, so LTP address mapping is frequently accessed. At the same time, as the storage capacity of UFS devices is increasing, the LTP size is growing, improving random read performance and reducing the cost of UFS controllers by hosting LTP in fast system DRAM and providing LTP prompts when sending I/O requests. Samsung, which was working on the development of HPB capabilities a few years ago, says it can improve random read performance by as much as 67%.
In summary, while UFS 3.1-compliant storage devices will continue to provide up to 23.2 bps (2.9GB/s) of theoretical maximum bandwidth with HS-G4, the bandwidth should be similar to 1.875GB/s, given the encoding using M-PHY 4.1. However, with Write Booster and Host Performance Booster, the upcoming UFS drives will be increasingly available. At the same time, deep sleep will help extend the battery life of low-cost devices.