Silicon Motion SM2504 XT Engineering Sample Review - Record Efficiency

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"Technology & Positioning
Earlier this year, Silicon Motion took the consumer PCI-Express 5.0 SSD market by storm with the release of their SM2508 high-end controller. It is currently used on some of the fastest drives on the market like the Crucial T710, WD SN8100, Kingston Fury Renegade G5, Lexar NM1090 Pro, ADATA Mars 980 Blade and Acer Predator GM9000. The SM2508 controller can effectively compete with Phison's E26 controller in the high-end Gen 5 market. However, in the mid-range segment, which relies on four-channel SSD controllers like the Phison E31T, Phison is currently unchallenged. This is why Silicon Motion is now focusing its efforts on entering this segment. Their upcoming SM2504 controller goes head-to-head with the Phison E31—it's a 4-channel DRAM-less design, too, which brings down cost, and it's fabricated at TSMC using their 6 nm node, for energy efficiency. The SM2504 engineering sample in this review uses TLC NAND flash, which I think is the preferred config, but I wouldn't be surprised if we saw models with QLC as well. Silicon Motion has requested that I don't publish details of the NAND flash used, but I can confirm that it is contemporary TLC, something that we've seen on other drives in the market—nothing yet-to-be-released. As mentioned before, the SM2504 is DRAM-less, which makes a lot of sense, because cost matters a lot in this segment.

Synthetic Performance
In our synthetic testing, the SM2504 didn't perform particularly impressively. It achieved decent upper mid-range scores but definitely fell short of claiming the performance crown. In the duel against its direct competitor, the Phison E31, represented by the Kioxia Exceria Plus G4 in our test group, it performed slightly better in sequential transfers and slightly worse in random IO. However, the differences are small. Where the SM2504 showed surprisingly weak results was in 4K random write, where it was one of the slowest NVMe SSDs. This looks like a firmware issue to me, no doubt, the final product will show better numbers here. It'll be interesting to see how much effect this has on our real-life performance testing—random write is a very rare activity for consumer SSDs. That's exactly why our real-life testing is important, it is designed to run actual applications, not disk traces that compress time by assuming infinitely fast hardware and software. We're even running those tests with the drives filled to 85% capacity, not empty. This approach puts additional pressure on the various algorithms and the SLC cache, just like in real-life.

Real-Life Performance
In our real-world tests, the SM2504 delivers highly impressive results that are very good, especially for a 4-channel drive. Numbers are very strong everywhere, not beating the fastest 8-channel Gen 5 drives, but very close. Overall, averaged over all tests, the drive ends up very slightly behind the SM2508 drives in our test group—very interesting. I expected a slightly bigger difference. On the other hand, SMI had a lot of time to optimize the algorithms in their drive, also based on the learnings from the SM2508 drives that have been in the market for quite a while now. A fast SSD is made up of smart algorithms, not brute force, and it looks like they learned a few new tricks. The best Gen 5 SSDS like the WD Black SN8100 and the Hynix P51 Platinum are still a few percentage points ahead, as expected. Compared to older Gen 4 drives, the performance uplift is between 10% to 1%, not unexpected, too. Still it's impressive to see how close the best Gen 4 SSDs still are. Compared to the Phison E31T-powered Kioxia Exceria Plus G4, the SM2504 is already 2% faster, with a non-final firmware. Very nice.

SLC Cache / Sustained Performance
Silicon Motion has configured their drive with a 216 GB SLC cache, which is a medium-sized SLC cache for a 2 TB drive. It means that 32% of the drive's capacity will be used in SLC mode first, which consumes three times the storage per byte, at much higher speed. Filling the whole 2 TB capacity completed at 2.2 GB/s, which is an excellent result that is better than most SSDs on the market. It's even more impressive for a DRAM-less SSD that does not use next-gen flash tech. What's also very important is that the direct competitor, the Phison E31T offers only half the speed in this test.

Power Consumption / Heat
Energy efficiency is extremely important for a Gen 5 SSD, because people don't want loud, fan-cooled heatsinks on their SSDs. I'm happy to report that SMI's SM2504 controller has set a new record for energy efficiency in our testing. It is the most efficient design for both read and writes, roughly 10% better than the SM2508. Phison's E31T isn't that much behind though. What I think is VERY important to highlight is that the controller chip is very thin, which means it will have difficulties making contact with a heatsink, if that heatsink covers the NAND flash chips, too, which are thicker. The gap is around 0.3 mm, which is quite a lot of thermal pad for heat to travel through. I'm not sure why they made it this thin, it definitely complicates heatsink design.

Pricing & Alternatives
Silicon Motion didn't provide any pricing for the SM2504. Given the current market situation, I think a realistic price point is around $180 for a 2 TB SSD. Phison E31T drives sit at exactly this price point, the faster 8-channel designs live north of $200, the Samsung 9100 Pro is even just $200 at the moment. At the other end of the spectrum are the various Gen 4 SSDs, like the WD SN7100 ($130), Samsung 990 Pro ($160) and WD SN850X ($150), and of course MaxioTech MAP1602 drives such as the Lexar NM790 ($120).

Due to the pre-release nature of the product tested, awards were not considered. If this was a final, shipping drive, at a price point of around $180 I'd give Recommended, at $160, Editor's Choice."

Source: https://www.techpowerup.com/review/silicon-motion-sm2504-xt-es/19.html