Phison E31T ES 2TB Review: The performance per watt champion

The drive of your dreams is almost here. High performance, good power efficiency, and PCIe 5.0 levels of bandwidth for today and tomorrow. Phison’s E31T SSD controller enables amazing things for storage when paired with the latest flash, promising all-new heights for whatever system you use. Coming just after our preview of Silicon Motion’s SM2508 controller, the E31T takes a different tack, building a drive for everyone rather than just enthusiasts. In many ways, that will be more impactful in the long run.

Phison, the undisputed leader in consumer SSD controller design — when you consider the raw cadence of its releases and industry firsts in recent years — is not without its share of growing pains. As the focus on R&D has increased, so have the troubles that come with being on the cutting edge. Phison has had some firmware issues in the last few years and even more recently, although in general these have not widely impacted users. Normally this might be something that hits one’s reputation, but every proprietary brand — WD, SK hynix, Samsung, and even Crucial with its MX500 — has had firmware issues in recent memory.

Which we bring up today because this E31T engineering sample needs to be taken within the context of it being a work in progress with novel technology. There may be a few final issues to iron out, but we anticipate that happening before drives using the E31T platform become available at retail. We aim for full disclosure of any and all problems when we review a new drive, as it’s best to report these failings so things get fixed and hopefully don’t happen again in the future.

To present one example, SK hynix — and Solidigm for that matter — have not issued a firmware fix for the Platinum P41/P44 Pro pSLC degradation problem. This has led to a slew of RMAs and negative reviews and forum posts. Phison, when presented with sufficient evidence over time of its own issues, fully tested, reported, and fixed any firmware problems. What that means is that we are willing to give it a chance to prove that lessons are learned moving forward.

The Phison E31T is a good example of that. This is really more of a preview than a review but we were under no obligation to treat it like the former. Its ability to stand up to review levels of scrutiny is part of what makes it exciting, but we remind you that there is still some work to be done.

Phison E31T ES Specifications

The specifications for the E31T indicate that it will come in 1TB and 2TB capacities with performance up to 10,300 / 8,600 MB/s for sequential reads and writes and up to 1,300K / 1,500K random read and write IOPS. It’s potentially possible to reach higher random read IOPS with this hardware, but the performance level is already high.

We suspect that 4TB drives are a foregone conclusion, but those may take a while longer to arrive. The controller is capable of handling up to 8TB with the right flash, but we would consider 2TB to be the sweet spot for this sort of hardware. At 1TB you can still get a lot of performance, though, and 4TB will have to compete against existing budget drives like the Teamgroup MP44.

Drives based on the E31T should have the standard five-year warranty with 600TB or more writes per TB capacity. That's subject to modification by the individual drive manufacturers once SSDs begin shipping, naturally.

Phison E31T ES: A Closer Look

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The drive consists of the SSD controller, two NAND flash packages, and the power management integrated circuit (PMIC). It’s single-sided, which is a bonus as that increases compatibility with host systems and can be easier to cool. It’s theoretically possible to do 4TB single-sided, which was not the case with the DRAM-equipped Crucial T500. However, we have seen 4TB on drives like the Crucial P3 Plus — with Phison’s E21T and four NAND flash packages — and the Lexar NM790, with the Maxio MAP1602 and four packages.

It might be challenging to handle 4TB or more at higher signal speeds in some cases, as the 4TB T500 does have extra circuitry for that. The E31T as designed is meant to have just two NAND flash packages, which could limit its potential to some degree, but it also means designs in other M.2 form factors are an easier task.

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The Phison E31T SSD controller probably has the most in common with the E27T. We’ve reviewed several drives using the latter, including the Sabrent Rocket 4 and the updated Corsair MP600 Mini in the M.2 2230 form factor. The E27T, in turn, is similar to the E21T, used to good effect on popular budget drives like the Teamgroup MP44L. All these controllers have the same basic hardware but with increasing clock speeds for the microprocessor. This is needed, in part, to keep up with increasing bus speeds, which is required to get the most out of newer flash for the highest performance levels.

The E31T is more than just a PCIe 5.0 version of the E27T, though. It has some improvements. The first is an upgrade in the LDPC error correction to a newer generation, which isn’t exciting on its own. Error correction improvements can heighten performance and/or NAND flash endurance and are necessary as I/O speed increases and we begin to see more 4-bit QLC flash, which is more sensitive to wear than 3-bit TLC flash in return for higher bit density or capacity. The bigger change for this controller is that it’s manufactured using TSMC’s 7nm, or N7, process node instead of the older 12nm FinFET. N7 is far more efficient and allows for high performance from a PCIe 5.0 SSD without requiring a heatsink.

It also helps get more performance out of a four-channel controller like the E31T. More powerful controllers like the E26 — see the Crucial T705 — have twice as many channels and DRAM. To get higher relative levels of performance out of the DRAM-less E31T, faster flash must be used, in this case 3600 MT/s BiCS8 TLC flash. As mentioned above, this means higher clocks and that translates to higher power consumption for the controller. The move to N7 helps nudge the E31T above any and all PCIe 4.0 SSDs without having to compromise with overwhelming heat output.

This is also the first time we’ve had a chance to see BiCS8 flash in action. It comes in at 218 layers with four planes and enhanced bonding technology which, among other things, continues the trend of improving power efficiency from circuit under array (CuA). It’s purportedly using a wafer bonded design reminiscent of YMTC’s breakthrough Xtacking technology, which we have discussed in the past as one way of handling the move to a higher layer count. Additionally, the move from two planes — common with BiCS5 flash, the WD Black SN770 being a fair sample — to four means higher bandwidth from increased parallelization.

BiCS8 also promises to have higher-density QLC flash, but for now we’re focusing on the TLC. The top question is probably how it handles 4K latency. Based on information released by WD and Kioxia, the read latency on this flash should be equal to or better than any other flash we’ve tested to date. We’ll put that to the test with CrystalDiskMark in a moment.

One possible reason BiCS8 performs so differently, as you will see, is because of the sub-plane design — this is something Samsung did a while back with its flash, splitting the typical 16KB pages into two 8KB sub-pages — while still using an edge rather than center decoder. A center decoder design can reduce latency further but the sub-plane architecture could compensate for now. The fact that E31T can push so much performance at 1TB, even with dense flash, is possibly due to this design. This is a pretty big change for BiCS in general but some further refinement is possible in the future, as we have already seen YMTC’s flash improve with every iteration. 

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