The HP FX900 is an excellent little drive that will help the proliferation of PCIe 4.0 SSDs. Thanks to its attractive pricing of just $105 for the reviewed 1 TB version, cost is no longer a reason to pick an older PCIe 3.0 SSD over the FX900. HP has chosen the Innogrit IG5220 controller and paired it with 176-layer 3D TLC NAND flash from Micron. A DRAM cache chip is not included for cost reasons, but the IG5220 seems to be well optimized to handle this scenario. With this hardware combo, the FX900 is identical to the ADATA XPG Atom 50. Of course, HP has possibly added some firmware tweaks the ADATA drive doesn't have or vice versa.

Synthetic test results for the FX900 are good, in line with what you'd expect from a decent PCIe 4.0 SSD. Sequential read at low IO depth is especially good, reaching 5400 MB/s, which is faster than the Samsung 980 Pro and Crucial P5 Plus. 4K Random Write is also really good, which is a bit surprising considering we're dealing with a DRAM-less design. Without looking at the actual PCB, I wouldn't have been able to tell that this is a DRAM-less drive, not from any of our tests. We've seen similar performance results from other modern DRAM-less drives, like the Samsung 980 non-Pro and WD Blue SN770. It seems controller vendors have figured out some new tricks on how to handle the challenges of a DRAM-less design. The HP FX900 has support for the Host Memory Buffer (HMB) feature, which allocates some system memory for use as replacement for the DRAM cache. Technically, the FX900 can use up to 512 MB HMB, but Windows will max out at 64 MB unless you play with the registry.

We ran a special round of testing to figure out how well the drive handles random writes—the weakness of all DRAM-less drives—and were surprised that for relatively small working areas, up to 5 GB or so, the FX900 performs very well. The numbers are almost twice as high as most older DRAM-less drives, and match the Samsung 980 and WD Black SN770—the best DRAM-less drives on the market. However, when we tested larger write areas, 15 GB and above, the numbers quickly dropped to levels in line with older models, almost an order of magnitude lower than the WD SN770. This doesn't have to be a dealbreaker as a consumer system is extremely unlikely to have workloads spanning such huge areas. What's important is that random writes for <10 GB areas are fast, which they are.

In our real-life test suite, the HP FX900 achieves astonishing results. It's one of the fastest drives we ever tested, faster than any PCIe 3.0 drive—even PCIe 3.0 with DRAM cache. Compared to high-end PCIe 3.0 drives, the performance difference is 3–10%, 15% compared to value Gen 3 SSDs. Only the fastest Gen 4 drives can achieve a meaningful performance uplift, but the differences are small—only 1–2%.

Thanks to a large SLC cache, the FX900 has good sustained write performance, especially considering its positioning. When mostly empty, the drive will store incoming data as SLC first, which is very fast at over 4.5 GB/s, but consumes three times the storage because it fills each three-bit TLC cell with just a single bit. This mode is active until most of the drive is filled, 280 GB in SLC mode consume 840 GB TLC capacity. Once that margin is crossed, the drive will switch into another mode which fills cells in TLC mode directly, storing three bits per cell, which is still very fast—2 GB/s. Beyond 480 GB written, the drive will aggressively flush data out of SLC into TLC so that there's enough space for incoming writes. Overall, this is a good result. Filling the whole 1 TB capacity completes at 800 MB/s on average, which is better than all value-oriented SSDs in our test group, but only roughly half of what we've seen on the best Gen 4 SSDs.

Thermal performance of the HP FX900 is impressive. The Innogrit controller is a highly energy efficient design that doesn't put out a lot of heat. In our worst-case thermal loading test, we couldn't get the drive to throttle even when throwing tons of data at it with no airflow. HP includes a preinstalled heatsink with claims of "graphene," a nano material with fantastic heat-transfer properties. This is actually the first graphene claim that is somewhat reasonable and not a total fantasy. The material used is not a thermal paste and resembles thin sheets, and it's brittle like graphite and electrically conductive like carbon. While that probably doesn't make it graphene in a strict sense, which requires the layers to be ordered, it probably is close enough to make such claims, especially from a marketing perspective. One could argue that since graphene is a single layer of graphite, the thin sheet on the heatsink is actually multiple layers of graphene. I can confirm that the heatsink works to reduce the SSD's temperatures, by around 5°C according to the internal sensor, and thermal throttling is avoided completely. I was curious and tested the drive without any heatsink installed, and it didn't thermally throttle either, so the magic is in the energy-efficient controller, not how it's cooled.

Priced at just $105 for the tested 1 TB version, the FX900 is one of the most affordable PCIe Gen 4 SSDs on the market that offers good performance. There are indeed similarly priced PCIe 4.0 SSDs available, but many of those use various older controllers that are not nearly as fast. People have been complaining about prices of PCIe 4.0 SSDs for a long time, and there's now finally an option that's just as affordable as the aging PCIe 3.0 drives out there. The only compromise is that the FX900 is DRAM-less, which is impossible to notice because of various optimizations. Of course, I wouldn't recommend putting this drive in a busy server with a write-heavy database of a several hundred GB, but such a workload is very difficult for all consumer drives.

Noteworthy alternatives are the WD Black SN770 for $115—the fastest DRAM-less SSD on the market—WD Blue SN570 for $100 or Kioxia Exceria for $85. Last but not least, the DRAM-less MSI Spatium M450 is a DRAM-less PCIe 4.0 design, too, but $20 cheaper than the FX900, with 5% lower performance. Still, if you want the absolute best price-to-performance, you should consider that drive, too. Of course, all these prices are always in flux and vary by geographic region. Bottom line, the HP FX900 is one of the best value SSDs you can buy today, and it comes at a very compelling price point, too—no more PCIe 4.0 tax.