Phison Details U21 USB4 PSSD and E31T Mainstream Gen 5 SSD Controllers

Phison's lineup of SSD and portable SSD controllers is keeping pace with the general industry trends, as evidenced by their products on display at the 2024 CES.

Portable SSDs in all forms and sizes (including the popular thumb drive as a SSD-in-a-stick) have gained a lot of market and mind-share in recent years, thanks to rising capacity and performance. An important contributor on the power-efficiency front (which is important for flash drive vendors to pack SSD performance in a thumb drive) has been the rise of native flash controllers like Phison's U17 / U18 and Silicon Motion's SM2320.

Since the launch of the U17 / U18 in 2021, USB4 has become common on client platforms from both Intel and AMD. SSD controller vendors are keeping pace with that update, and Phison is officially the first out of the door with their U21 USB4 eSSD controller. (Note: It appears that the PSSD nomenclature promoted by SSD vendors is being replaced by eSSD on the controller side). Similar to the U17 / U18, these are single-chip solutions. Small thumb drives may also end up using these in a multi-chip package (where the flash and the controller are packaged together to save on area).

Phison indicated that the U21 controller can practically saturate the USB4 bus with speeds up to 4000 MBps. Fabricated in TSMC's 12nm process, the U21 can support up to four channels with 16 chip enables. Backwards compatibility is an important aspect. USB4 requires compatibility with only USB 3.2 Gen 2, USB 3.2 Gen 1, and USB 2.0 for certification purposes. However, the U21 can also work in the USB 3.2 Gen 2x2 (20 Gbps) mode if required. Phison's customers can use this controller for PSSDs ranging in capacity from 512GB to 8TB. Both TLC and QLC NAND can be used. Flash speeds of up to 1600 MT/s is supported. This might hold back the power- and energy- efficiency a bit, as we have seen higher flash speeds getting the job done faster and having lower overall energy consumption for a given workload. Higher flash speeds also reduce the number of required channels for a given performance target, and that results in power savings too. It remains to be seen if other eSSD controller vendors support 2400 MT/s flash later this year.

In internal SSD controller news, Phison is also readying the E31T mainstream Gen 5 controller for launch this year. As the naming convention goes, this is a DRAM-less controller suitable for mainstream M.2 2280 SSDs with a focus on low power operation (suitable for mobile platforms). This quad-channel controller is fabricated in TSMC's 7nm process with peak performance numbers of around 10800 MBps for sequential workloads and 1.5M IOPS for 4K random accesses.

Support for TCG Opal / Pyrite ensures that the E31T platform can also be used for OEM SSDs meant for business deployments.

Phison also had the X2 enterprise SSD platform on display. This is a Gen 5 x4 dual port U.2 solution (also available in E3.S form factor) with steady state sequential performance of 14 GBps for reads and 12 GBps for writes. Random read IOPS are at 3M, and write IOPS are at 0.8M.

Phison's X1 platform was adopted by Seagate in the Nytro 5050 Series, and it is likely that we will see the X2 come to market with a different performance profile / firmware tuning when the Nytro series get an update.