Phison at CES 2021: New USB SSD Controllers, Adds E21T For Low-End NVMe


At CES 2021, Phison gave us the usual updates on their SSD controller roadmap. The most significant new products coming this year are a pair of USB flash drive controllers for high-end portable SSDs, designed to compete against current solutions that combine a USB to NVMe bridge chip with a standard NVMe SSD controller. Phison is also planning to introduce a new entry-level DRAMless NVMe SSD controller later this year. Xeon Platinum 8176M

Phison U17 and U18 USB 3.2 SSD Controllers

For portable SSDs, Phison is introducing the U17 and U18 controllers. The U17 uses a USB 3.2 Gen 2x1 (10Gb/s) host interface and a two-channel NAND interface running at up to 1200 MT/s. The U18 doubles these: USB 3.2 Gen2x2 (20Gb/s) and a four-channel NAND interface. The performance specs may look lackluster compared to Phison's NVMe SSD controllers, but they are pretty close to saturating what their respective USB host interfaces can handle, and performance will be competitive with NVMe+USB bridge based portable SSDs. However, the U17 and U18 will have a significant power efficiency advantage, lower cost and smaller PCB footprint than existing portable SSDs. Phison will also be providing TCG Opal encryption support on the U18, enabling a level of security they say is impossible to achieve with NVMe+USB bridge solutions.


Phison USB 3.2 SSD Controller Comparsion
Host InterfaceUSB 3.2 Gen2x1USB 3.2 Gen2x2
NAND Interface2ch, 1200 MT/s4ch, 1200 MT/s
Max Capacity1 TB4 TB
Error Correction4th Gen LDPC
TCG Opal SupportNoYes
Sequential Read1000 MB/s1900 MB/s
Sequential Write800 MB/s1700 MB/s
4KB Random Read (TLC)185 MB/s260 MB/s
4KB Random Write (TLC)260 MB/s330 MB/s

Phison expects to finish qualification of the U17 and U18 controllers later this month. We're hoping to get a performance preview shortly thereafter by testing their reference designs, and retail products should be showing up within the next several months.


Phison E21T: Low-End NVMe Moves to 12nm

For NVMe SSDs, the only new controller Phison is talking about this year is the E21T, their latest DRAMless NVMe controller. This is a follow-up to the E19T controller, which has seen very little use in retail consumer SSDs but has actually been outselling their high-end E16 PCIe 4.0 controller due to strong demand from OEMs (especially from an unnamed customer with a very popular gaming product). With the E21T, Phison is finally moving this product segment from 28nm to 12nm fabrication, which allows for performance and power improvements of about 25% compared to the E19T. The basic architecture hasn't changed much for the E21T: it's still a 4-channel controller managed by a single ARM core plus Phison's proprietary coprocessors. Performance has increased significantly, with peak throughput now rivaling the high-end E16 controller (though real-world performance on heavy workloads may still be slower due to the downsides of a DRAMless controller design).

Phison is planning to start sampling the E21T to customers around June of this year with mass production ramping up in Q4—around when we should start seeing PCIe 4.0 SSDs catching on with notebook OEMs. Most of the drives using the E21T will probably pair it with QLC NAND, and Phison has performance projections for what we can expect when using Micron's 176L QLC.


Phison E21T QLC SSD Performance Projections
Capacity512 GB1 TB2 TB4 TB
Form Factor, InterfaceM.2 2280, PCIe 4.0 x4
ControllerPhison E21T
NAND FlashMicron 176L 3D QLC
Sequential Read4.5 GB/s4.8 GB/s
Sequential Write1.65 GB/s3.3 GB/s4.5 GB/s
Random Read IOPS (4kB)250k500k780k
Random Write IOPS (4kB)350k700k800k

It's likely that many of the product lines currently using the E16 controller with QLC NAND will switch over to using the E21T in future generations, since the DRAMless E21T will be a cheaper overall solution. However, the 4TB limitation will be an issue for the handful of companies that have already started shipping 8TB QLC SSDs. Those 8TB M.2 SSDs currently use the E12 controller and its PCIe 4.0 successors are not available in a reduced-size package like the E12S variant. So 8TB PCIe 4.0 SSDs will probably have to push the limits of NAND packaging by stacking 16 dies per package in order to leave enough PCB space for an E16 or E18 controller plus DRAM.


Phison NVMe SSD Controller Comparsion
Market SegmentMainstream ConsumerHigh-End Consumer
28nm12nm28 nm12 nm
CPU Cores1x Cortex R51x Cortex R51x Cortex R52x Cortex R53x Cortex R5
Error Correction4th Gen LDPC3rd Gen LDPC4th Gen LDPC
Host InterfacePCIe 3.0 x4PCIe 4.0 x4PCIe 3.0 x4PCIe 4.0 x4
NVMe VersionNVMe 1.3NVMe 1.4NVMe 1.3NVMe 1.4
NAND Channels, Interface Speed4 ch,
  800 MT/s
4 ch,
  1200 MT/s
  1600 MT/s
8 ch,
  667 MT/s
8 ch,
  800 MT/s
8 ch,
  1200 MT/s
Max Capacity2 TB2 TB4 TB16 TB16 TB16 TB
Sequential Read2.5 GB/s3.75 GB/s5.0 GB/s3.4 GB/s5.0 GB/s7.4 GB/s
Sequential Write2.1 GB/s3.75 GB/s4.5 GB/s3.2 GB/s4.4 GB/s7.0 GB/s
4KB Random Read IOPS350k440k780k700k750k1M IOPS
4KB Random Write IOPS450k500k800k600k750k1M IOPS
Controller Power1.2 W1.6 W 2.1 W2.6 W3.0 W
SamplingQ2 2019Q4 2019Q3 2021Q2 2018Q1 2019Q1 2020
Retail SSD
Q4 2019Q1 2020?Q4 2021?Q4 2018Q3 2019Q4 2020

For high-end NVMe SSDs, Phison's E18 finally started shipping in late 2020. Phison is pretty proud of this controller, and makes much of the fact that they're the only ones so far hitting at least 7GB/s for both reads and writes. Phison plans for the E18 to be their last flagship PCIe 4.0 controller; they're already looking forward to PCIe 5.0, and the E18 will remain their top of the line controller for probably another two years. This doesn't mean Phison is entirely done with the E18. They're still working on firmware tuning, especially around thermal management and trying to squeeze out a little bit more performance at low queue depths. There will also be continuing firmware updates to support newer generations of 3D NAND flash memory. Current E18 drives are using Micron 96L TLC, but Micron has started production of their 176L NAND. Phison expects to finish qualification with that NAND in March, so a second round of E18 drives should start arriving in April with 10-15% performance improvements.

Phison's older E13T controller is also still around as a low-cost and low-power solution for entry-level NVMe applications. It's particularly popular as a controller integrated into BGA SSDs, where it helps displace eMMC storage is devices like Chromebooks, tablets, and maybe even some smartphones.


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