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

Silicon Motion is back, and it’s not content to sit on its laurels after the amazing SM2508 launch. It’s here to take the fight to Phison's E31T in the mid-grade PCIe 5.0 SSD segment with its new SM2504XT SSD controller, and it isn’t pulling any punches. We took the new SSD for a spin on an electronic sample (ES) platform to assess its performance.

The combination of high performance, 10+ GB/s transfers, and excellent power efficiency makes the SM2504XT ES a pretty sweet solution. The SM2508 gave us our first feeling of a real next-gen drive, and the SM2504XT is the less-expensive but no less successful follow-up.

While high-end, eight-channel, DRAM-equipped drives are the way to go for enthusiasts, not all SSDs have to be the pinnacle of perfection. Dropping DRAM and some bandwidth can create a better solution for laptops, mobile devices, and small-form-factor desktops. These drives pull less electricity but are still very powerful in their own right. The only real downside might be the capacity limitation. These drives are also kind of an odd pick if you’re putting them into a PCIe 4.0 M.2 slot because of the added cost over last-generation alternatives, but in time, the newer hardware will make that decision easier. After all, almost nobody buys PCIe 3.0 drives anymore.

After some time with the drive, we can’t help but feel impressed by what SMI has managed to do here and with the SM2508. Competition is a good thing, and SMI has come better prepared this time around. Waiting for 6nm technology was in some ways a wise decision as PCIe 5.0 is still in the process of growing its user base. We certainly think more efficient drives are the way to go either way, even if the impact is relatively small for most PCs. Less power means less heat, and heat is the enemy of hardware.

The SM2504XT ES just feels like a next-gen drive – we got the same feeling in our SM2508 preview – and we have no trouble embracing this kind of progress.

SMI SM2504XT ES Specifications

The SMI SM2504XT ES drive being tested today is 2TB, but this four-channel controller should be sold within the 512GB to 4TB range. 8TB is also possible with 2Tb dies, but we expect this drive to be most popular at 2TB. The controller can reach up to 11,500 / 11,000 MB/s for sequential reads and writes and up to 1,700K / 2,000K random read and write IOPS. This is roughly on par with the Phison E31T controller, used on the Corsair MP700 Elite and several other drives. We would give the peak performance edge to the SM2504XT, though.

The controller does support the TCG Opal 2.0 specification, so drives based on it could optionally support hardware encryption. We expect a normal warranty of five years with 600TB of write endurance per TB of capacity, or more.

SMI SM2504XT ES Software and Accessories

The ES itself doesn’t come with any software, but third-party partners will offer their own solutions. Usually, this means an SSD toolbox and Acronis True Image, although some toolboxes may offer imaging and backup functionality separately. For free applications, we recommend CrystalDiskInfo for S.M.A.R.T. and health monitoring, MultiDrive for imaging and backup on Windows, and Clonezilla for imaging and backups with a bootable solution.

SMI SM2504XT ES: A Closer Look

Image 1 of 2

Yes, the SM2504XT is a single-sided design. It’s only using one NAND flash package for 2TB, which suggests a sixteen-die package (16DP) if it’s using standard 1Tb dies. This is interesting as the drive could be sold in a shorter form factor, and it can handle at least 4TB of capacity in single-sided form factors. We cannot show or directly discuss the flash for confidential reasons, although we have some suspicions as to why.

The same policy was true for our SMI SM2508 preview, and, at the end of the day, it didn’t make much difference. The SM2508 ES used BiCS6, whereas release drives now use superior BiCS8 and 232- or 276-layer Micron TLC flash; the retail drives performed better, if anything. On the other hand, it’s likely that the flash on the SM2504XT is contemporary, so our results with this ES should be closer to what we’ll see in retail.

The SMI SM2504XT is built on 6nm technology – the Phison E31T is listed as 7nm, which is almost comparable. The E28 was initially listed as 7nm but is actually 6nm, so things can change. In either case, the node enables it to be very efficient. It’s DRAM-less with four flash channels at up to 3,600 MT/s, which, with overhead, puts a cap around 11.5 GB/s. Each channel has four chip enable signals, totaling 16, which means 32 dies should be possible. However, with current flash, this limit is reached at 4TB. However, we wouldn’t be surprised if 2TB were a more common maximum point for third parties.

Future 2Tb dies could double the maximum to 8TB, which might help 4TB become more common; however, that’s also somewhat deceptive. QLC flash is likely to see such implementation first, but enterprise demand has kept it from being affordable in the consumer space. 2Tb TLC yields may be lower at first, especially for dense die packages. So we would advise managing your expectations if you’re hoping for a lot of capacity with this controller in the near term.

The controller is built with a triple-core Arm Cortex-R8 processor, which means a lot of power, delivering up to 2 million IOPS. This was unthinkable for a “budget” drive not that long ago, although real-world benefits are only derivative of this. More IOPS can mean reduced latency, for one, which is downstream of newer flash with higher I/O speeds. Faster flash also increases bandwidth, which can bring improvements even at lower, more realistic queue depths, such as you find with file transfers. Therefore, it’s important to put this power into context – it’s a shortcut method of classifying the drive in comparison to what came before.

MORE: Best SSDs

MORE: Best External SSDs

MORE: Best SSD for the Steam Deck