Silicon Motion SM2262EN Preview: Micron 96-Layer TLC

Introduction, Specifications, and Pricing

The race is on for companies to increase densities with low-cost commodity flash. Micron leads in bit density with efficient 64-layer technology but plans to have 96-layer memory in production before the end of 2018 according to CEO Sanjay Mehrotra.

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To date, two controller designers have displayed Micron's 96L memory technology. Our first sighting came at Computex where Maxiotek paired the memory with a low-cost SATA controller. Silicon Motion also displayed working 96L memory just a few doors down from Maxiotek at Computex. The Silicon Motion drive falls on the other end of the performance scale, in the premium NVMe sphere.

We've already detailed the Silicon Motion, Inc. SM2262EN controller in a next-generation preview that also featured Phison's PS5012-E12. Both drives utilized 64L TLC memory with the SMI paired with Micron's exemplary TLC and Phison with Toshiba's Toggle2 BiCS FLASH. In the article, we stated the Phison would likely ship with Toshiba 64L BiCS FLASH, but the SM2262EN would only come with 96L IMFT memory as none of SMI's partners planned to release the updated controller with 64L memory. q

Armed with that knowledge we wanted to test the SM2262EN with Micron's upcoming memory. Today we get to do just that.

Specifications

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Silicon Motion's reference design specifications haven't changed with the memory update. These rarely go through updates as each SSD manufacturer will tune firmware to favor different aspects of performance and that affects the marketing numbers.

The SM2262EN improves on the SM2262 by increasing the write performance. The latest NVMe controller from the company pushes sequential writes to 3,000 MB/s, up from 1,900 MB/s. Random performance increases to 420,000 IOPS read and write from 370,000 read and 300,000 write on the SM2262.

Both controllers share the same 8-channel 4CE design with a PCIe 3.0 x4 interface to the host system. Communication comes over the NVMe 1.3 protocol.

Even though very few companies chose to enable real-time full disk encryption on SM2262 released products, the feature carries over to the new SM2262EN. The controller also supports end to end data path protection and SRAM ECC. The controller supports 4th generation NANDXtend ECC technology with 2KB codeword LDCP.

On paper, it looks like the changes could be entirely program related, but the SM2262EN features some internal hardware changes that make it different from the previous version. The latest version includes an additional data path designed specifically for writing data. This bypasses the firmware handling and provides a streamlined path from the host to the flash.

A Closer Look

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Our sample with 96L memory doesn't look much different from the 64L sample. We wouldn't even notice the memory change without the updated sticker that proudly shows B27A, Micron's code for 96L TLC memory.

There isn't a lot of information available for B27A. The information is under lock and key behind Micron's password-protected website. We're not too worried about the fine details at this point. Both 64L and 96L feature a 667 MT/s bus speed.

Interestingly enough, the SM2262EN also supports bus speeds up to 800 MT/s. That should make it ready for faster memory should it emerge. Toshiba's BiCS4 supports Toggle3 at 800 MT/s.

1TB Class Performance Testing

Product Comparison

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Silicon Motion has a number of popular NVMe SSDs on the market today with the SM2262 controller. We limited ourselves in the comparison charts to just two, the Adata SX9200 960GB and the HP EX920 1TB. We also included the Intel 600p, one of the first entry-level NVMe SSDs to come to market. It uses the SMI SM2260, the predecessor to the SM2262.

We also included four drives, not in the SMI camp. The Plextor M9Pe and SanDisk Extreme Pro NVMe both utilize Toshiba/SanDisk 64L TLC. The Samsung 970 EVO and Pro utilize Samsung 64L memory. The 970 Pro is the only product in the charts with 2-bit per cell memory.

The one controller not represented is the new Phison PS5012-E12. We will have our first retail drive with the E12 today, but it will take a few days to complete testing. You can read about the MyDigtialSSD BPX Pro later this week.

Testing Notes

The SMI SM2262EN with 96L IMFT memory is not a retail product with final production firmware. This is a reference design with generic firmware used for development and compatibility testing. At some point in the near future samples with go to SMI's partners and the companies will begin working on custom firmware based on individual requirements. Some companies may choose to limit random performance in order to decrease power consumption for notebook users. Other companies may target specific thermal limits or maximum performance.

The reference design would ideally be in the middle. It will not win every performance benchmark. It's not optimized in the same way the SM2262 drives are. In short, the performance will increase when the SM2262EN retail drives come to market.

Sequential Read Performance

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We start the testing with sequential read performance. At queue depth (QD) 1 the latest SM2262EN starts with identical performance to the Samsung 970 Pro. The SM2262EN takes a little longer to ramp up as we increase the workload compared to the optimized previous generation models from Adata and HP. Starting at QD4, the SM262EN starts to show real strength by outperforming all of the other drives before coming back in line with the 970 Pro.

Sequential Write Performance

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The sequential write performance test shows the SM2262EN outperforming every other drive across the QD range except at 2 where the SanDisk Extreme takes a 7 MB/s lead. Overall, the SM2262EN is a big winner in the sequential write burst test where it outpaces the 970 Pro by a hundred megabytes per second.

Sustained Sequential Write Performance

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As we mentioned on the first page, the SM2262EN is highly modified for superior burst performance. In our sustained sequential write test, we see the cache write speed is higher than everything else shipping today. The cache comes in different tiers with a large SLC buffer, then an MLC or MLC-like buffer. The two combine to deliver very high write speeds for 25% of the overall capacity, but force a much lower native TLC write speed outside of the 25% range. This is a dynamic cache, so the buffer shrinks as you add data to the flash.

Random Read Performance

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Random read latency is the user experience. These very small file size reads make up the brunt of a consumer workload. When the latency is low, you feel like the PC is moving briskly, but in turn, high latency feels slow. This is where Optane shines bright, and where flash technology improves with each new generation.

Even in its current state, the SM2262EN with next-generation Micron memory manages to raise the bar over the optimized HP EX920. On the next page, the gains in this workload will come through in the real-world consumer applications.

Random Write Performance

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The SM2262EN with Micron 96L flash breaks new ground in low queue depth random write performance. This is the advanced cache at work. The latest SMI NVMe technology increases random writes at QD1 by close to 7,000 IOPS, and that grows even more at QD2.

70% Read Sequential Performance

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The one area where we found the next generation components lacking is sequential mixed workloads. The SM2262EN stays well over 1,000 MB/s in our burst test but trails the previous generation and many of the other drives in the charts today. This is likely due to the lack of optimization at this stage in the development process.

70% Read Random Performance

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We saw much better performance in the random mixed workload test. The SM2262EN leads both the random read and write workloads, so it's able to just muscle through this test in the same way higher pressure water rushes through a fire hose.

1TB Real-World Testing

Game Load Time

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On the previous page, we showed a number of random workloads where the SM2262EN with 96L memory dominated the charts. The higher random performance allows this combination to perform faster in real applications.

In this test, we use the Final Fantasy: Stormblood benchmark to measure how long it takes to load game levels. The SM2262EN comes out on top but only does so by a small margin over the HP EX920. This is the first flash-based SSD we've tested to outperform the optimized EX920.

PCMark 8 Total Storage Bandwidth

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PCMark 8 uses storage traces from nine applications to run ten tests. The applications vary in workload and length to give a broad range of storage scenarios. The SM2262EN performs about the same as the HP EX920 in this test.

PCMark 8 Extended Storage Test

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The Extended Storage Test uses the same nine applications but removes the idle time between each trace. This forces the drives into steady-state early and then continues to work the drives with a heavy workload until the five recovery phases. The recovery phases allow a five-minute idle time between each iteration of the nine tests. The idle time allows the drives to process data-management tasks, like garbage collection.

The SM2262EN performs much better than the SX8200 and EX920. The drive is very cache dependent, so it takes longer to recover compared to the 970 Pro with MLC memory. Most users will never see this level of heavy workload after the first day of installing an operating system and applications.

SYSmark 2014 SE System Responsiveness and Power Tests

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For most of our readers, the SYSMark 2014 SE Responsiveness Test is the most important. This is a direct measurement of the user experience through latency. We use a Lenovo Y700-17 gaming notebooks to run the software suite. The suite uses a number of real software applications from Microsoft, Adobe, and Chrome.

The SM2262EN with Micron 96-layer memory is the first non-Optane drive we've run that outperforms the HP EX920. The SM2262EN took a sizable lead in a test where every few points is a noticeable difference.

Final Thoughts

We've seen 96L flash memory from two sources now, Toshiba (XG6 Preview) and Micron. Even though the XG6 comes with a model number, it's an OEM drive that ships in a number of different configurations. Because of that, we don't consider either drive to be a final retail representation of what will come to market. We do get a very good look at the silhouette. What we don't have is Samsung's Toggle4 96-layer that could upset everything with it's 1,200 MT/s bus speed.

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The way the market sits right now Micron's 64-layer memory is what you want in your SSD. The flash allows the controllers to deliver exceptional random read latencies. In one generation, Micron leaped over both Toshiba and Samsung beating both at the latency game while simultaneously using CMOS-Under-Array technology to increase bit density by shrinking the footprint on the wafer.

In respect to retail products, Micron's 3rd generation TLC (96L) builds on the lead started with the 2nd generation. Even in its optimized form, the SM2262EN paired with Micron's 96L memory is already superior to the products shipping now with the previous generation technology. We've heard that 96L should enter production in the next six weeks. That would put retail announcements in line with the end of October or early November.

Our testing shows moderate, but consistent performance increases in almost every test. The performance we see now is the baseline. We can all but guarantee more increases as firmware development and customization continues.

From the evidence we've seen thus far, I'll be the first in line to buy the next generation SSDs using the SM2262EN with Micron 96L flash. The latency improvement in BAPCo SYSMark Responsiveness Test sold me.