SMI SM2504XT ES 2TB SSD Review: A Mid-Range PCIe 5.0 Challenger

Comparison Products

The SMI SM2504T ES’s top competitors are E31T-based drives with the newest flash: the Crucial P510, with Micron’s newest TLC, and the Kioxia Exceria Plus G4 with BiCS8 TLC. Other competitors include higher-end PCIe 5.0 solutions, such as the early adopter Sabrent Rocket 5, the high-end DRAM-less Biwin Black Opal X570, and the SM2508-based Adata Mars 980 Blade. The final one uses last-generation Micron TLC flash, so it’s more of a semi-budget option compared to the true high-end drives, such as the Crucial T710 and the Sandisk WD_Black SN8100.

If you’re considering upgrading from a PCIe 4.0 solution or might want to leapfrog it from a PCIe 3.0 SSD, you also want to see how the SM2504XT ES compares to the most popular PCIe 4.0 drives. For such analyses, we have the high-end, E18-based Kingston KC3000, the fast but DRAM-less E27T-based Inland TN470, and WD’s SN770. These three drives, or comparable drives in each class, are probably the most popular options for those seeking something fast but affordable in the PCIe 4.0 space. If you’re looking for something more like the Samsung 990 Pro or WD Black SN850X, then you’ll probably be reaching over and beyond the mid-range PCIe 5.0 drives. This is especially true if you want the maximum capacity possible – see our 8TB Samsung 9100 Pro review for something more your speed, in that case.

Trace Testing — 3DMark Storage Benchmark

Built for gamers, 3DMark’s Storage Benchmark focuses on real-world gaming performance. Each round in this benchmark stresses storage based on gaming activities including loading games, saving progress, installing game files, and recording gameplay video streams. Future gaming benchmarks will be DirectStorage-inclusive and we also include notes about which drives may be future-proofed.

Image 1 of 3

The SM2504XT ES takes first place in our 3DMark testing, beating even the high-end Rocket 5 by a smidge. This performance is not as good as the record-holding Sandisk WD_Black SN8100, but it’s on par with some of the better Crucial drives. This suggests that the flash on this drive could be 232- or 276-Layer Micron or, alternatively, Sandisk/Kioxia BiCS8 TLC, but we’re not going to speculate too much. However, we think it’s fine to highlight it here because one of the SN8100’s selling points is its fantastic latency, and the SM2504XT – which is, on paper, not supposed to compete with the very best – has a very impressive showing here.

Trace Testing — PCMark 10 Storage Benchmark

PCMark 10 is a trace-based benchmark that uses a wide-ranging set of real-world traces from popular applications and everyday tasks to measure the performance of storage devices. The results are particularly useful when analyzing drives for their use as primary/boot storage devices and in work environments.

Image 1 of 3

The SM2504XT ES again takes first place, although the competition is a bit closer this time. The Rocket 5 is still way up there, and we see that the 980 Blade is also within striking distance. The latter drive uses SMI’s SM2508 controller, which has DRAM, along with 232-Layer Micron TLC flash, which is an older technology. The controller’s technology is similar to that of the SM2504XT, so this may hint at what flash is in use here.

Console Testing — PlayStation 5 Transfers

The PlayStation 5 is capable of taking one additional PCIe 4.0 or faster SSD for extra game storage. While any 4.0 drive will technically work, Sony recommends drives that can deliver at least 5,500 MB/s of sequential read bandwidth for optimal performance. In our testing, PCIe 5.0 SSDs don’t bring much to the table and generally shouldn’t be used in the PS5, especially as they may require additional cooling. Check our Best PS5 SSDs article for more information.

Our testing utilizes the PS5’s internal storage test and manual read/write tests with over 192GB of data both from and to the internal storage. Throttling is prevented where possible to see how each drive operates under ideal conditions. While game load times should not deviate much from drive to drive, our results can indicate which drives may be more responsive in long-term use.

Image 1 of 3

We think you can do better for the PS5 than this if you’re trying to be cost-efficient. There are many drives that will cost less while offering the same experience. That said, this drive would run cool in the PS5 and would perform excellently.

Transfer Rates — DiskBench

We use the DiskBench storage benchmarking tool to test file transfer performance with a custom, 50GB dataset. We write 31,227 files of various types, such as pictures, PDFs, and videos to the test drive, then make a copy of that data to a new folder, and follow up with a reading test of a newly-written 6.5GB zip file. This is a real world type workload that fits into the cache of most drives.

Image 1 of 3

The SM2504XT ES finally hits a snag, although this is largely due to its inability to fully utilize the PCIe 5.0 interface. Four channels can and will saturate this link someday, but for now, this is about as good as it gets with 3,600 MT/s flash and 6nm technology. The drive remains impressive, outperforming all PCIe 4.0 drives and coming close to the P510.

The P510’s Phison E31T controller is comparable to the SM2504XT, so this makes sense. In fact, it’s very close, and we remind the reader that the P510 uses 276-Layer Micron TLC flash. The E31T is more mature and potentially better optimized, so we would say the hardware on these two is equivalent without knowing more about retail drives based on the SM2504XT.

Synthetic Testing — ATTO / CrystalDiskMark

ATTO and CrystalDiskMark (CDM) are free and easy-to-use storage benchmarking tools that SSD vendors commonly use to assign performance specifications to their products. Both of these tools give us insight into how each device handles different file sizes and at different queue depths for both sequential and random workloads.

Image 1 of 14

The ATTO results look good. The fact that this drive can even get up to Rocket 5 levels of performance in some areas is incredible. We only see a minor dip at 128KiB for reads, which could be a nuance of the controller or an anomaly. We observe a similar drop with the P510, which may indicate that a similar flash is used on both of these drives.

Standard CrystalDiskMark sequential performance yields excellent results at both QD1 and QD8. The SM2504XT ES, in fact, beats the X570, which has eight channels, in three out of the four.

Eight channels still help when you want maximum write throughput, and adding DRAM to the package gets you better results for reads and writes. Just see the Rocket 5. The SM2504XT ES actually appears to be punching above its weight, which helps sell it as a mid-level PCIe 5.0 drive. Usually, you have to give up something to meet its expected price point, but if it can match or beat the X570, then it’s creeping up on being a high-end option in its own right. It’s only held back by having a weaker capacity potential.

Calling it high-end would be a less persuasive argument if the drive had poor 4K latency; however, the SM2504XT ES has excellent read latency and good write latency at low queue depths. It’s effectively a match for BiCS8 or 232-Layer Micron TLC flash – see the Exceria Plus G4 and 980 Blade, respectively – with reads and writes on par with older high-end drives, such as the Rocket 5 and KC3000. It also beats the X570 by a little bit. Write performance isn’t quite as important, so that is a good place for some compromise, especially as it still matches some very capable drives.

Sustained Write Performance and Cache Recovery

Official write specifications are only part of the performance picture. Most SSDs implement a write cache, which is a fast area of pseudo-SLC (single-bit) programmed flash that absorbs incoming data. Sustained write speeds can suffer tremendously once the workload spills outside of the cache and into the "native" TLC (three-bit) or QLC (four-bit) flash. Performance can suffer even more if the drive is forced to fold, which is the process of migrating data out of the cache in order to free up space for further incoming data.

We use Iometer to hammer the SSD with sequential writes for 15 minutes to measure both the size of the write cache and performance after the cache is saturated. We also monitor cache recovery via multiple idle rounds. This process shows the performance of the drive in various states as well as the steady state write performance.

Image 1 of 3

The SM2504XT ES’s faster, single-bit pSLC cache mode writes at 10.44 GB/s for just over 22 seconds. The cache is a little over 230GB, which is a good size: it’s not too large and not too small. This allows the drive to maintain almost 2.1 GB/s when in native TLC mode, which is quite good. After some time, the drive is able to recover some of the cache and can reach a higher average steady-state write speed of 2,545 MB/s, which is good for a four-channel controller. This drive would be a fine choice in an external enclosure all the way up to Thunderbolt 4, if you are so inclined.

One could look at the P510 and point out that it has a similar TLC speed but achieves a significantly higher steady state. This isn’t surprising as the P510’s cache is small in comparison. We think it’s possible that Crucial opted for a more conservative cache in the P510 after receiving feedback on the T500, an excellent drive that had some issues with sustained writes, even after a later firmware update.

If the P510 happens to use the same flash as the SM2504XT ES, then the speed difference won’t matter for some applications – if you’re limited by an enclosure’s interface even up to USB4 40Gbps speeds, for instance – but in desktop use, the P510 could be better for some niche applications. To put it more simply, both drives have consistent write performance, but they are tuned slightly differently.

Power Consumption and Temperature

We use the Quarch HD Programmable Power Module to gain a deeper understanding of power characteristics. Idle power consumption is an important aspect to consider, especially if you're looking for a laptop upgrade as even the best ultrabooks can have mediocre stock storage. Desktops may be more performance-oriented with less support for power-saving features, so we show the worst-case.

Some SSDs can consume watts of power at idle while better-suited ones sip just milliwatts. Average workload power consumption and max consumption are two other aspects of power consumption but performance-per-watt, or efficiency, is more important. A drive might consume more power during any given workload, but accomplishing a task faster allows the drive to drop into an idle state more quickly, ultimately saving energy.

Image 1 of 3

The SM2504XT ES SSD controller boasts excellent power efficiency, ranking first by a narrow margin over the Exceria Plus G4. The Exceria Plus G4 and P510 use the same controller as each other, but the former has BiCS8 flash instead of Micron’s flash, which makes us favor the former drive for power efficiency. Kioxia historically does a good job of refining its firmware, but we still think it’s the BiCS8 doing the lifting in this case. The SM2504XT is a different controller, and we don’t have much information on it with regard to efficiency. We would assume it’s equal to or probably better than the E31T, but we can’t be sure without knowing the flash for certain.

Our guess is that the SM2504XT is more efficient given SMI’s architecture, and there are some clues to support this conclusion. The first is that the Exceria Plus G4 has lower max power consumption, while the P510 has more, which suggests the SM2504XT ES might be using less-efficient flash than BiCS8. Coupled with the relatively good idle power consumption – remember, we’re testing under the worst-case scenario – in which the SM2504XT outperforms both the Exceria Plus G4 and P510, those two being tied, the implication is that the ES’s controller consumes less power than the E31T. This also provides us with another hint about what flash is being used, but given this is an ES, we won’t risk making a firm conclusion. We’ll have to wait for retail drives and firmware to do that. Instead, we’ll just say that this drive would be fantastic for laptops, portable devices, and HTPCs in any configuration.

Test Bench and Testing Notes

We use an Alder Lake platform with most background applications such as indexing, Windows updates, and anti-virus disabled in the OS to reduce run-to-run variability. Each SSD is prefilled to 50% capacity and tested as a secondary device. Unless noted, we use active cooling for all SSDs.

SMI SM2504XT ES Bottom Line

The SMI SM2504XT is an excellent drive with solid all-around performance, good sustained write performance, and excellent power efficiency. We can’t give it a higher score for a couple of reasons, though. The first is that this is just an engineering sample, and we need to see retail drives to fully give it our endorsement. Part of that is because we don’t know where these drives will be priced, although we would expect them to land close to E31T-based drives like the Crucial P510. We also don’t know what capacities we’ll see, although matching the E31T shouldn’t be difficult.

Second, we would like to see drives using the SM2504XT compared with different flash. At the end of the day, it doesn’t matter too much for subjective performance – these drives are insanely fast by any consumer measure – but it would be nice to have different implementations, including cache configurations, to make some drives more interesting. The P510, for one, has a unique caching scheme that makes us like it a lot for use in faster external enclosures. The Exceria Plus G4, on the other hand, utilizes BiCS8 TLC flash, making it more efficient than the P510. If SM2504XT-based drives can have a similar variance, then we would definitely consider this controller a winner.

Lastly, this controller has limited potential. Four channels and these I/O speeds, which are reasonable if you want to maintain high power efficiency, are not enough to fully saturate PCIe 5.0. That’s fine, but it also means this drive will never be a 5/5, especially since there’s no DRAM. That doesn’t make it a bad drive, just not the fastest.

The channel count also reduces the maximum capacity, which is one place where a drive like the Biwin X570 – or even the Acer Predator GM9000 – can beat it. That said, we think this solution is fantastic for mobile platforms and laptops, although most of those devices are still relegated to PCIe 4.0 M.2 slots. That’s fine, as this drive would be even more efficient there, but you’re paying more for less overall benefit.

What we can say for sure is that the SM2504XT SSD controller and platform is very exciting, even though Phison beat SMI to the punch with its E31T. There’s room for both, as laptop sales always trump desktops, but we think budget-seekers will stick with PCIe 4.0 drives for now. SMI did beat Phison to the high-end game with the SM2508 controller, which is also very efficient, and we’re glad that the company is being competitive again. We don’t see anything we don’t like in the SM2504XT ES, and if the launch is smooth, then we’ll be back with further solid scores.

MORE: Best SSDs

MORE: Best External SSDs

MORE: Best SSD for the Steam Deck