M.2 SATA vs M.2 PCIe: Differences, Test and Best Options

Against the backdrop of classic 2.5-inch solid-state drives, the newfangled M.2 looks like a real miracle of technology: miniature, thin, lightweight and does not require additional wires. However, not all M.2 SSDs are equally fast, and not all are compatible with your specific desktop or laptop, even with the proper connector on the motherboard. We will tell you about the various intricacies and intricacies of choosing M.2 SATA Vs M.2 PCIe in this article.


M.2 SATA Vs M.2 PCIE: Difference and specifications

At first glance, all M.2 SSDs look the same. But often a disk that fits into the corresponding slot without any problems is not displayed either in the operating system or even in the BIOS menu. And even on closer inspection, the differences are noticeable: the M.2-drive connector has one or two notches (missing pins), which are called B-key and M-key.

Thus, drives with two B&M keys, although made in the new M.2 format, operate on the outdated SATA 3 bus (approximately 560 MB / s). Simply put, they are just scaled-down versions of the old-school 2.5-inch SSDs. However, many laptops, in particular those with the sixth and seventh generations of Intel Core processors (Skylake and Kaby Lake), are only compatible with M.2 SATA drives.

Laptops, starting with the eighth-generation Intel Core (Kaby Lake Refresh, Whiskey Lake) and above, already support M.2 drives with the PCI-E bus (also called NVMe) and a single key M. Desktop motherboards began to equip a slot M.2 with support for both buses (SATA and PCI-E), starting with the Intel Z97 chipset (fourth-generation Haswell Refresh processors).

In addition, the bandwidth of the PCI-E bus can differ significantly. For example, the aforementioned Z97 chipset allocates only two lines of version 2.0 for the needs of the M.2 SSD (labeled as PCI-E 2.0 x2, approximately 1000 MB / s). Modern budget Intel H310 chipset – four lines version 3.0 (PCI-E 2.0 x4, 2000 MB / s). More functional modern chipsets from Intel (B360 and higher) and AMD (A320 and higher) PCI-E 3.0 x4 (3600 MB / s). And the most advanced chipsets AMD X570, TRX40, and, probably, the upcoming B550 – four lanes of the latest PCI-E 4.0 standard (up to 7000 MB / s). You want to know about M.2 Vs 2.5 SATA SSD. Read the articles in detail.

Test for M.2 SATA Vs M.2 PCIE

Now let’s move from theory to practice and take a closer look at the functional differences between M.2 SATA and M.2 PCI-E SSDs using the example of the latest models from Western Digital Red SA500 M.2 and Blue SN550 1 TB.

M.2 SATA solid state drive :WD Red SA500 M.2 WDS100T1R0B 1 TB 

M.2 SATA solid state drive: WD Red SA500 M.2 WDS100T1R0B 1 TB 


  • A powerful controller,
  • high-in-class read and write speed even for large files,
  • a solid IOPS,
  • a separate RAM-cache chip,
  • and an increased rewriting resource.  


  • Not compatible with some newer notebooks that exclusively require M.2 PCI-E SSD. 

Check Price at Amazon

The WD Red SA500 M.2 is Western Digital’s “Red Series” solid-state drive designed de jure for RAID arrays, NAS storage, home, and small office servers. But given that WD Red’s main focus is on increased reliability and durability, it makes sense to use this SSD in both desktop and laptop PCs for professional work. The volume can vary from 500 GB to 2 TB.

As you might guess from the name, the drive is made in the new-fashioned M.2 form factor. The connector has two B&M keys, which clearly indicates the use of the SATA 3 (6 Gb / s) interface. This leads to a ceiling for linear speed: 560 MB / s for reading and 530 MB / s for writing. The above interface is simply not able to miss any more. Although select WD / SanDisk’s own flash memory chips (now one company) such as 3D TLC BICS 3 are clearly capable of more.

The high potential of the chips is confirmed by the solid sequential write speed of very large amounts of data at a time after exceeding the virtual SLC array – as much as 400 MB / s. This is four times faster than most other TLC SSDs, and eight times faster than budget QLCs. A separate DDR3 buffer memory chip adds even more performance.

The “brain” of the WD Red SA500 M.2 is a dual-core, eight-channel Marvell 88SS1074 controller, capable of delivering as much as 95 and 85 thousand IOPS (input-output operations per second) at random reading and writing of the smallest files, respectively. This, again, is the ceiling for SATA SSDs. Exactly the same controller as the flash and RAM memory chips is installed in the 2.5-inch version WD Red SA500 WDS100T1R0A 1 TB That is, the disks differ only in form factor.

Overall, the WD Red SA500 M.2 is undoubtedly one of the fastest M.2 SATA SSDs on the market. It successfully combines a multichannel controller, a separate RAM buffer chip, and select flash memory to guarantee high write speeds even for very large files. And the rewriting resource of the terabyte model is more than 600 TB, and the warranty is 5 years. The WD Red SA500 M.2 has a more affordable twin brother WD Blue SSD 3D NAND M.2 WDS100T2B0B 1TB  but with a lower operating time and a reduced warranty (400 TB, 3 years). 

The main thing is, before buying, check if your PC or laptop has an M.2 slot and if it exactly supports M.2 SATA drives.

Facing problem M.2 SSD Heat Issues check solution in the blog.

M.2 PCI-E Solid State Drive: WD Blue SN550 WDS100T2B0C 1 TB 

M.2 PCI-E Solid State Drive: WD Blue SN550 WDS100T2B0C 1 TB 


  • Powerful controller,
  • high-in-class read and write speed even for large files,
  • very high IOPS,
  • little heat,
  • 5-year warranty.  


  • Not compatible with some older laptops that exclusively require M.2 SATA SSD.

Check Price at Amazon

The WD Blue SN550 is a new wave of affordable M.2 NVMe SSDs (M key). Compared to the previous WD Blue SN500 WDS500G1B0C 500GB operating on the narrowed x2 bus, the new SN550 operates with four full PCI-E lanes. There are three volume options: 250, 500 GB, and 1 TB (the predecessor had only two lower volumes). The rewriting resource of the older terabyte version is 600 TB, and the warranty period is 5 years.

Built WD Blue SN550 based on the latest proprietary WD / Sandisk controller, code-named 20-82-01008-A1. Its technical characteristics are still classified, but, most likely, it is something in between, between 20-82-007010 from SN550 and the top-end triple-core 20-82-007011, used in WD Black SN750 NVME SSD WDS100T3XHC 1TB with heatsink. The linear speeds of the WD Blue SN550 are not record-breaking, but still very decent: 2400 MB / s for reading and up to 1950 MB / s for writing.

And even after the virtual SLС array overflows, the sequential write speed remains quite high – about 900 MB / s, which is more than double the performance of even top-end SATA SSDs, not to mention the budget ones. WD / Sandisk semiconductor factories have achieved such a high density of storage cells (96 layers) that even with a maximum SSD capacity of 1 TB, flash memory is represented by one single chip.

In order to reduce the cost, the WD Blue SN550 is deprived of a separate RAM buffer chip (but a small buffer is nevertheless integrated directly into the controller) and a metal heatsink. Cooling, however, does not require it it is relatively cool even under prolonged load. In addition, the radiator would have to be dismantled if you wanted to install the disk in a laptop, candy bar or nettop. Simply put, every penny is invested in the speed of the SSD, and not an additional optional body kit.

A powerful controller paired with a high density of memory cells allows the WD Blue SN550 to process the smallest files at speeds up to 410 thousand IOPS. Previously, only significantly more expensive flagship SSDs could boast of similar results. But for many tasks and professions, for example, programmers working with database management systems (DBMS), IOPS is much more important than linear speed in megabytes per second.

Check the article on How To Connect Hard Drive To Laptop?


Making the right choice of which of the two subtypes of M.2 SSDs is right for you is not too difficult. Just by the mere appearance of the drive, namely the presence of one or two B&M keys, one can understand on which bus it works: SATA or PCI-E. It should be borne in mind that the speed of a PCI-E SSD may be limited by the interface version (2.0, 3.0, 4.0) and the number of lines (x2, x4), which depends on the motherboard chipset. M.2 SATA drives now make sense to buy, perhaps only if you have a relatively old laptop that only supports them. But if your laptop or desktop is equipped with an M.2 slot of at least PCI-E 2.0 x4, you will get at least a double performance boost over SATA. In the case of more modern chipsets, the difference in speed can reach five or even ten times. Especially,