Things You should know about PCIe SSDs

Things You should know about PCIe SSDs


PCIe SSDs have only just appeared on the market and have already proven their potential with higher transfer speeds than any other SSDs. But every new thing comes with a lot of questions and we are here to answer them. If You want to know more about PCIe drives then this article is for You. To see our comparison of PCIe SSDs, go HERE.

What are PCIe SSDs?

It’s pretty much what it says on the can. They are solid state drives that connect to Your computer via the PCIe (Peripheral Component Interconnect Express) port. Pretty much all previous SSDs use the SATA (Serial AT Attachment) port but SSDs are beginning to have more speed than the bus can handle. Here is a list of SATA and PCIe versions and their according bandwidth:
Interface Bandwidth, MB/s
SATA 1.0 150
SATA 2.0 300
SATA 3.0 600
SATA 3.2 1969
PCIe 1.0 250 per lane
PCIe 2.0 500 per lane
PCIe 3.0 984 per lane
PCIe 4.0 1969 per lane


The difference here doesn’t seem too big, but the “per lane” part changes everything because PCIe can have up to 16 lanes in one slot. For example, Kingston Digital Hyper-X Predator uses PCIe 2.0 x4 slot. The number that comes after the “x” determine how many lanes are in the slot, which means x4 has 4 lanes and accordingly the speed of 4 version 2.0 lanes – 2GB/s. The read/write speeds of Hyper-X Predator are over 1GB/s, meaning the SATA bus would become a bottleneck and prevent the drive from using its full potential. More and more high-end SATA SSDs show transfer speeds of around 550 MB/s, which shows that SATA is starting to become a limitation for upgrading Your drive.


Why have SATA in the first place?

Why have SATA in the first place?
If the PCIe interface is faster, why not use it to begin with? The answer to this question takes us back in the history of computer hardware. In the olden days, PCs were full of huge, clunky parts and fat cables and lot of devices that are now integrated into laptop motherboards were expansion cards back then, so spacing had to be optimized. That is why SATA came along, so hard drives could have their own slot. Up to recent history, SSD speeds weren’t too big for SATA to handle, so manufacturers didn’t bother engineering new drivers for PCIe. (Read more about SSDs) But now there is both space in computers and the need for a faster port, making this the only next step in the evolution of drives.


Main things You should know about PCIe

Main things You should know about PCIe
The main question most people ask when choosing a new piece of hardware is weather or not it will work with their computer. With PCIe the answer will almost always be yes. When it comes to versions, all of them are compatible with one another – PCIe 2.0 is backwards compatible with PCIe 1.0 and PCIe 3.0 is compatible with both 2.0 and 1.0. Even though the speeds of the port can vary, it will most likely be enough for the needs of SSDs. 
When it comes to the slots themselves, You can stick any smaller card into a bigger slot. For example, an x1 card will work just fine into a x16 slot. Although sometimes this may result in other slots losing speed. It is also possible to put a bigger card into a smaller slot because it only needs the first lane to work, but You can do this only with the help of an adapter, or by modifying the motherboard and making the smaller slot open-ended. This will most definitely cut down the speeds of the device, since it won’t be using all of its lanes.


M.2 review
As the PCIe SSDs started coming along, so did the M.2 specification for computers. For now not so many computers have this connection, but its popularity is growing. Computer parts are becoming smaller and smaller all the time and the M.2 form factors are the next stage. There are different form factors to M.2 cards, usually shown by four or five digits – the first two show width in mm and the remaining digits show length. For example, one of the form factors that M.2 SSDs have is 2280, meaning its 22 mm wide and 80 mm long. M.2 was also designed to allow a unified, simple connection to PCIe, SATA and USB buses, so M.2 supports not only SSDs, but also Wi-Fi, Bluetooth, satnav and other cards, depending on the key of the card. 
Keys are notches between the pins of cards and are marked by letters A to M (although most of them are reserved for future purposes right now), which determine the interfaces Your card may use. There are corresponding keys in the host connector too, so there are not only different cards, but different sockets as well. 
Now more about M.2 PCIe SSDs. They use either the B or M keys as B allows connection to PCIe x2 and M allows connection to PCIe x4 slots. Cards that use x2 will most likely have both B and M keys, as this ensures compatibility if you have only one – B or M socket. Faster cards will only have the M key for an x4 slot, because in this case having two keys means losing precious pin connections that ensure greater transfer speeds. Be careful before purchasing an M.2 SSD, check what keys Your sockets have to not waste money. It is a relatively new specification for computers at this point, so check if Your computer has this connection at all! Right now these different connections may cause problems, but as the popularity of this standard will grow, these issues will most likely be fixed.

We hope our short summary of things You should know about PCIe SSDs helped You understand more about this technology. If You have more overall questions, leave a comment and we will add the answer to the article. You can find more specific stuff in the links below:


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