The Silicon Power XS70 uses the highly popular hardware configuration of the Phison E18 controller with Micron 176-layer TLC NAND. We did have the chance to preview an engineering sample from Phison back in May 2021 and have in recent months seen these fantastic drives come to market. Phison is on the right track to becoming a premium SSD controller vendor. If you've read our other Phison E18 reviews, the Silicon Power XS70 PCB should look familiar to you—it matches the Phison reference design exactly. Just like Kingston, Team Group, and Corsair, Silicon Power took the Phison design and used it for their own product. This is certainly a valid approach as Phison probably knows best how to design an SSD that works well with their own controller. In terms of physical design, it's also worth mentioning that a DRAM cache is included for the mapping tables of the SSD, which helps with random writes.

Synthetic performance numbers of the XS70 are really good; all results are near the top of our charts. Sequential read claims the #1 spot in our test group, with 5.6 GB/s, and sequential write is second-best with 5.1 GB/s. Random IO results are excellent as well, higher than the major competitors WD Black SN850 and Samsung 980 Pro, albeit only by a small margin. No doubt a lot of optimization went into getting these synthetic scores high enough to beat the other drives. That's why our real-life testing is so important—it runs actual applications, something that's much harder to optimize for. Our real-life testing is also performed with 80% of the drive filled, which is a more realistic scenario and limits the drive in the way it uses its pseudo-SLC cache.

In our real-life test suite, the Silicon Power XS70 achieves excellent results, too. It matches the Samsung 980 Pro and beats the Corsair MP600 Pro by 2%. As expected, the XS70 matches the Kingston KC3000, which uses the same hardware configuration. Only the WD Black SN850 is a tiny bit faster—1%. Compared to the fastest PCI-Express 3.0 drives, the difference is around 2–5%; of course more depending on the workload. More value-oriented PCIe 3.0 drives are 15% slower, and the aging SATA drives are around 25% slower; SATA QLC even by 40–50%.

The pseudo-SLC cache size of the Silicon Power XS70 is within the "typical" range by today's standards. While the Kingston KC3000 runs all its cells in SLC mode first and then has to juggle data out of SLC into TLC while handling incoming writes, Silicon Power's drive has a much bigger margin, which gives it a higher speed once the SLC cache is full. Filling the whole capacity completed at 1.7 GB/s, a good result, the fourth-best in our test group. The Samsung 980 Pro achieves 1.9 GB/s in the same test, and the Kingston KC3000 2.0 GB/s—not a big difference. Of course, momentarily stopping the write activity will have the SLC cache free up capacity immediately, so full write rates are available as soon as you give the drive a moment to settle down.

Silicon power includes a preinstalled heatsink, which looks nice and is compatible with the Sony PlayStation 5. In our thermal stress test scenario that gets most Phison E18 drives to throttle, we couldn't even find a hint of throttling. Seems Silicon Power picked an excellent heatsink design for the XS70. I also like that the heatsink isn't just attached by the stickiness of the thermal tape, but four screws to really tighten things down securely.

Priced at $130 for the tested 1 TB version, the Silicon Power XS70 is VERY affordable for a PCIe 4.0 drive. Actually, it's cheaper than most competing drives: Samsung 980 Pro ($140), Kingston KC3000 ($170), WD Black SN850 ($150), Corsair MP600 Pro ($160), and T-Force Cardea A440 Pro ($170). Out of those, I might be tempted to prefer the Samsung 980 Pro since it's priced "close enough" and has the bigger brand name, but the others simply can't offer anything the XS70 doesn't have—except that the XS70 is more affordable and includes a preinstalled heatsink that works very well. Out of the PCIe 4.0 drives on the market, the only alternative I can think of is the ADATA XPG Atom 50, which costs $120, performs 1% worse, and is DRAM-less. Definitely worth considering if you're willing to make the speed compromise are PCI-Express 3.0 drives, which are only marginally slower but can be found for slightly better pricing closer to $100. If you want a PCIe 4.0 drive, the Silicon Power XS70 should be near the top of your shopping list.