With the growing demand for today's latest games and the trend toward fast solid state storage for these games, it is no surprise that demand for 4TB NVMe SSDs is skyrocketing. We have good news for you, too. As this excellent Lexar NM790 proves, these 4TB drives aren't so expensive anymore.

Consider this price. Lexar charges 5 cents per gigabyte. Let me indulge me for a moment as I look through our historical test data: back in 2013, SATA speed storage would have cost about 41 cents per gigabyte. It is truly astounding how much cheaper SSDs have become over the past decade.

This Lexar NM790 is much faster than the older SATA SSDs in our archives. At 7,400 MB/s sequential read and 6,500 MB/s sequential write, it is quite close to the speeds allowed by the Gen4 PCIe interface. In my own testing, I measured 7,106 MB/sec sequential read and 6,504 MB/sec sequential write. This is almost as good as advertised, which is truly impressive.

It is also quite fast under random workloads, which would make for a much snappier system. Read speeds of 75 MB/sec and transfer speeds of 291 MB/sec are among the fastest of the Gen4 and Gen5 drives we have tested.

These are all very impressive numbers for a DRAM-less drive.

Lexar differs from many of the other drives we looked at. We have come to expect high-end Gen4 drives to rely on Phison's very popular E18 controller, but that is not the case with Lexar. It uses the MaxioTech MAP1602A controller, which is not well known in the US and EU markets. For this reason, it behaves distinctly differently from more popular controllers in our tests, but not in a bad way.

For one thing, the drive is cool under load: while copying a 30 GB test folder (moderate load), the maximum temperature was only 57°C. This is about basic level with an ambient temperature of about 23°C. When transferring a steady stream of over 200GB of data, which may not be that frequent in real-world use, the temperature measured was 72°C. This is a respectable temperature for a fast spinning drive with no active cooling solution.

The NM790 uses SLC caching to achieve its advertised write speeds. Most modern drives use some form of SLC caching to speed up the initial file transfer, as native NAND technology cannot keep up. This means that SSDs operate as single layer cell (SLC) NAND with a portion of triple layer cell (TLC) or quad level cell (QLC) NAND; SLC is much faster than TLC or QLC, but because it stores less data per cell. Once the file transfer is complete, the SSD begins shifting data from the SLC cache to the TLC NAND, freeing the SLC cache for further transfers. However, when the file transfer exceeds the size of the available SLC cache, the drive begins to use slower NAND instead. [The NM790 uses 232-layer TLC NAND from YMTC, and improves on this with a large SLC cache buffer. how fast the SLC cache and this native TLC NAND are can be A simple IO test can test how fast this native TLC NAND with SLC cache is.

I threw a large continuous stream of data at the NM790 and plotted that data on the graph below. The fast initial transfer of about 6,400 MB/s shows the SLC cache at work. The next drop off around 100 seconds is the moment when the fake SLC cache is erased and the drive writes to the TLC NAND instead; although considerably slower than SLC, the NM790's TLC NAND itself is not that slow, delivering about 2,500 MB/s.

The test also allows us to examine the amount of Lexar's 4TB capacity that can be used as a faster SLC cache before defaulting to native TLC. The NM790's performance was slowed by one steady write transfer to the drive at approximately This was after writing 642 GB of data. As the drive fills up, the size of the SLC cache gets smaller, but with a 4TB drive there is plenty of room to play before that happens.

Importantly, you don't have to rely on the speed of TLC NAND as much. Even today's largest games are nowhere near the size of 642GB, and it's unlikely to transfer that much without a break; with a little extra room in the SSD, the SLC cache will get back up to full performance.

I thought the last wave of SSDs really maximized the potential of PCIe Gen4 drives, and given that the first wave of Gen5 drives is coming, most of the exciting new developments in controllers and NAND will be for faster interfaces that can be utilized. However, Lexar is proving otherwise. You can now get high-capacity SSDs with performance comparable to many of today's top-rated Gen4 NVMe SSDs, but for less money.

If your machine has a spare Gen4 slot and you desperately need more gaming storage capacity, we highly recommend looking into the Lexar NM790 to fill that slot.