The ADATA XPG Spectrix S40G is the first M.2 SSD with adjustable RGB lighting on the market. It uses a clever combination of eight LEDs and a diffusor to create the illusion of a smoothly illuminated drive. ADATA's software is easy to use, offers a lot of predefined patterns, and gives you plenty of control to match the lighting to your case's color theme. Unlike many other solutions, you're not forced to connect an additional cable to the drive that supplies power to the LEDs and transmits RGB control commands—ADATA is handling everything over the S40G's NVMe PCIe interface. The only drawback I could find is that the drive does not remember its RGB settings, so after power-off, it will use the default pattern again until the ADATA software launches during Windows startup. This requires you to always keep their software installed on your PC, and it shuts out users of other operating systems, like Linux. Recent graphics cards with RGB-control are able to save their settings in the RGB controller chip, so it shouldn't be hard for ADATA to add this capability on future SSDs.

In terms of performance, we see excellent results from the Realtek RTS5762 controller and Intel TLC flash due to DRAM cache and a large write cache. Overall, when averaged over our real-life benchmarks, the Spectrix S40G is just a hair behind the fastest NVMe drives we ever tested—2%. This puts the drive on a performance level similar to the Intel 760p, WD Black, Samsung 970 EVO, Samsung 970 Pro, and ADATA SX8200 Pro. Realtek's controller really shines when it comes to low-queue-depth sequential read performance, where it claims the top spot of all drives in our test group. Other synthetics are solid too, a bit behind some competing drives, but real-life performance is what counts in my opinion.

Modern TLC-based SSDs operate a portion of their flash in SLC mode to achieve higher rates for bursty loads, as writing in SLC mode is much faster than writing in TLC mode. While we typically see SLC caches in the 10 GB region, the Spectrix S40G takes a different route. Instead of SLC, the Realtek controller uses MLC mode, which is slower than SLC mode, but fast enough with over 2 GB/s. The benefit is that MLC caching effectively doubles the size of the cache because it stores two bits per cell, while SLC stores only one bit. A somewhat surprising test result is that the S40G will always write in MLC mode until the disk is completely full. Only then does it switch to TLC, which means it has to work extra hard then, moving existing data out of MLC into TLC to make space for incoming data while handling incoming read/write requests from the OS. As a result, when in that state, write performance is significantly reduced, down to around 400 MB/s. Averaged, we see 600 MB/s sustained write, which is very decent—much better than QLC, better than most SATA drives, and comparable to many NVMe TLC SSDs.

Thermal performance is decent; the drive can take several hundred gigabytes in full-speed writes before it starts throttling (at above 80°C). Throttling happens in several steps, which ensures performance doesn't fall off a cliff immediately, and it recovers quickly should temperatures drop again. Still, it would have been nice had ADATA added a bit more cooling capability to their RGB diffusor by making it out of metal, for example, with small fins, and thermal tape instead of just sticky tape to attach it. On the other hand, this would affect the design language of the product, which arguably could be considered more important in an RGB-illuminated SSD.

Some earlier RGB SSDs experienced thermal problems because the LEDs added heat on top of the heat output of the SSD itself. I did some quick testing in both idle and at high-speed write, comparing LEDs on vs off. In both scenarios the drive temperature increased by only 1°C, which is pretty much negligible.

Priced at $160 for the 1 TB version, the ADATA XPG Spectrix S40G isn't cheap. While it is more affordable than some competing offerings, like the WD Black, Samsung 970 Evo and Pro, our favorite NVMe performance SSD, the ADATA SX8200 Pro clocks in at $150, and budget options that do compromise a bit on performance retail for around $110-$120. If you can live with the reduced performance, the cheapest QLC drives even go for $100. Neither of those alternatives have what makes the XPG Spectrix S40G stand out—RGB lighting, and charging extra for that unique capability is expected. Overall, the XPG Spectrix S40G is an excellent high-performance SSD that also offers plenty of bling.