Let's get into the issue of bus type in a little more depth. Oftentimes, you won't have a choice of what bus variety you need. But you need to know some background to figure out what you have and what you should buy. Serial ATA (SATA) is both a bus type and a physical interface. SATA was the first interface that consumer SSDs used to connect to motherboards, like the hard drives that preceded them. It's still the primary cable-based interface you'll see for 2.5-inch solid-state drives. The SATA interface is capable of sequentially reading and writing a theoretical maximum of 600MBps in an ideal scenario, minus a bit for overhead processes. Most of our testing has shown that the average SATA drive tops out at roughly 500MBps to 550MBps; in sequential tasks, the real-world difference between the best SATA drive and a merely average one is pretty small. However, there's also the matter of 4K random read and write performance speeds to consider. These speeds reflect how quickly the drive performs in day-to-day tasks. (Think booting Windows, launching games, loading levels in those games, or working in applications like Adobe Photoshop.) For most gamers and general users, 4K random read/write speeds are going to determine how much you actually feel the "speed" of a drive. They should be the most important spec to keep in mind if you plan on turning your next SATA-based SSD into a boot drive or backup storage for your trove of games or creative projects. SATA-based SSDs have shown that in 4K random read and write, specifically, SATA isn't quite out of the game yet, offering performance in loading games or applications that's on par with... The original implementation of the PCI Express interface for SSDs took the form of cards that occupied one of the PCIe slots on a desktop motherboard, and you can still find carrier cards that let you plug M.2 drives into a standard PCIe slot. Nowadays, though, the most popular PCI Express SSDs mount into an M.2 slot, though as we said above, you should make sure that your M.2 slot (assuming you have one in the first place) supports PCIe drives before you make your purchase. Some support only the SATA bus; some support PCIe only; and some support both. A further wrinkle around the PCIe bus: All recent drives and slots support a transfer protocol known as NVMe (for Non-Volatile Memory Express). NVMe is a standard designed with flash storage in mind (opposed to the older AHCI, which was created for platter-based hard drives). In short, if you want the fastest consumer-ready SSD, get one with NVMe in the name. You'll also need to be sure that both the drive and the slot support NVMe. (That's because some early M.2 PCIe implementations, and drives, supported PCIe but not NVMe.) Then there's the difference between PCI Express generations. As you'd expect, drives speed up through each successive generation. PCIe 4.0 set peak-sequential speed records for consumer storage, and the first PCIe 5.0 drives have predictably blown these records away. PCIe 4.0 requires support from the specific desktop or laptop platform. PCIe 4.0 came to market with third- and fourth-generation Ryzen processors from AMD, and PCI Express 4.0 support is now available on the Intel side with Intel 500 Series chipset and later platforms with 11th to 14th Generation CPUs on the desktop. (It's also part of the company's mobile chip platforms from the 11th Generation onward. Indeed, the very latest desktop Intel platforms support the emerging PCIe 5.0, whose system requirements are more onerous than PCIe 4.0.) Most folks won't need (or indeed even be able to leverage) the speed of PCIe 5.0. On the market, you will find two main iterations of PCI Express drives in production right now: PCIe 3.0 x4, and PCIe 4.0 x16. (The "x" in each of these naming schemes refers to how many lanes the drive has available to transfer data.) PCIe 3.0 x2 drives exist, but avoid them at this point. A mainstream choice is a PCIe 3.0 x4 drive; you'll want a faster PCIe 4.0 model if you have a AMD Ryzen-based desktop based on the X570, B550, TRX40, or later chipsets, or an Intel-based desktop with an 11th to 14th Generation processor. Either way, you need a motherboard that explicitly supports PCIe 4.0 or 5.0 on an M.2 slot. (Check the specs for PCI Express 4.0 support, and on which slots, before you dive in.) Even PCIe 3.0 is significantly faster than SATA in straight-up sequential tests, though. But that's just sequential speeds, and how fast a drive can copy a folder from one part of itself to another isn't all that matters these days. There's also the issue of capacity,