The Silicon Power UD90 is the first SSD that we test that's built using Phison's new E21 controller, designed as a modern replacement to the E19 that powered drives such as the MSI Spatium M450 and WD SN750SE. While the E19 was PCIe 4.0 too, the E21 is an upgraded design built on a 12 nanometer production process at TSMC, definitely improving heat output and thermals. For NAND flash, Silicon Power opted for the highly-popular Micron 176-layer 3D TLC—can't go wrong with that. As expected, for cost reasons, a DRAM cache is not included, but the E21 controller is especially optimized for DRAM-less operation.

Overall synthetic performance results of the UD90 are very impressive. The drive is actually topping our charts, which is unexpected given the market positioning of the drive. Recent Phison-based SSDs have always shown excellent synthetic results; it seems the E21 has been optimized even more for synthetic benchmarks on a mostly empty drive—the way most reviewers test. That's why our real-life testing is so important—it runs actual applications and games, which are 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.

The real-life performance is very decent, it matches the best PCIe 3.0 SSDs (that have eight channels and DRAM-cache)—quite an impressive feat. An important win is that the UD90 can match the DRAM-less Samsung 980 SSD, and it's just 1% behind the Hynix Gold P31—the fastest PCIe 3.0 SSD we ever tested. Modern PCIe 4.0 drives are still slightly faster than the UD90. For example the DRAM-less XPG Atom 50 (IG5220) and the WD Black SN770 are several percent quicker on average, with bigger differences depending on the application. The MSI Spatium M450, which is based on Phison's previous E19 controller is 4% slower, confirmation that Phison has achieved solid improvements with their new controller design. Against value PCIe 3.0 SSDs, the performance uplift is around 10%, aging SATA drives are 25-40% slower.

Just like all other modern TLC drives, the UD90 comes with an SLC cache that absorbs incoming writes at high speed, but uses three times the storage to do so. Our testing reveals that the SLC cache is sized at 64 GB, which is surprisingly small for a solid-state drive in 2022. On the other hand, sustained write performance is better than most competitors—we were able to fill the whole 1 TB capacity at 1.2 GB/s, which is a huge improvement over drives such as the WD Blue SN570 (590 MB/s), Samsung 980 (600 MB/s), WD Black SN770 (630 MB/s) and XPG Atom 50 (805 MB/s).

Silicon Power does not include a heatsink with the UD90, and that's no problem at all. Even in our worst-case thermal load testing, we couldn't get the drive to thermally throttle. Actually, temperatures were very decent, with only 77°C after the drive got hammered with hundreds of GB of incoming writes. The secret sauce is Phison's new controller design, which, as mentioned previously, is produced on a highly efficient 12 nanometer production process, bringing with it better energy efficiency and leading to lower heat output—good job, Phison.

The Silicon Power UD90 currently sells for around $110, and is somewhat difficult to find in many markets. At that price point, the drive is priced competitively to many alternatives, but ultimately loses in both price and performance to SSDs like the WD Black SN770 ($95), WD Blue SN570 ($80) and XPG Atom 50 ($110). Especially WD is very aggressive with their pricing at the moment—the WD Black SN850 is only $110—a very compelling choice. Prices are always in flux and vary geographically, but I feel like a sub-$100 price point would definitely help the UD90 achieve additional sales against these drives from very strong brands.