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TekSpek Hard Drives
Intel PCI-E SSDs

Intel PCI-E SSDs

Date issued:

Perhaps the best PC innovation in the last 10 years has been the solid-state drive (SSD) used to store the operating system and programs on your computer. SSDs have begun to replace the older mechanical disks as the primary storage for the PC and it's not hard to see why.

Silent operation, low power consumption, fantastic speeds and the ability to read and write small files on a completely different scale to the clunky spinners makes SSDs the only choice for a modern system. Such positive accolades do come at a cost, of course, but it's now possible to purchase a quality 256GB SSD for under £70.

Consumer SSDs - comprised of little more than a controller chip and flash memory - are usually packaged in a 2.5in case and connect to the system via a SATA data cable and a separate power cable from the supply. Yet the tiny footprint occupied by the controller and flash memory enables manufacturers to produce ever-smaller printed circuit boards (PCBs) that pave the way for different form factors. This TekSpek examines the common consumer SSD form factors in 2015 and explains why PCIe-based drives perform the best.

M.2 - PCIe

Ultra-slim laptops often don't have room to fit a standard 2.5in drive into the chassis, and for this reason the mSATA form factor was developed in 2009. Offering the same performance as a regular SATA drive but in a considerably smaller footprint, mSATA has been popular in small-form-factor PCs and Ultrabooks.

Now, though, a new form factor is taking over from mSATA as the go-to choice for tiny SSDs. Formerly known as Next Generation Form Factor but now referred to as M.2, this new specification allows for the SSD-holding PCBs to be between 16mm and 110mm long. All M.2 drive use a common connector to interface with the motherboard thereby ensuring interoperability between devices. These small SSDs connect to a system via either the regular SATA6Gbps protocol or, for the more adventurous and faster drives, via the faster PCI Express conduit that has a clear pathway directly to the motherboard's chipset.

M.2 drives using a SATA6Gbps connector are limited to real-world transfer speeds of around 600MB/s read and write thus matching what's on offer from the regular 2.5in-based drives. There are a select few that, instead, have a PCIe interface for higher potential performance. The following table shows why PCIe, in its various speed flavours, is the preferred interface for ultimate performance.

Interface Real-world speed
SATA 6Gbps 600MB/s
PCIe 2.0 x2 800MB/s
PCIe 2.0 x4 1,600MB/s
PCIe 3.0 x4 3,200MB/s

Though the same-sized M.2 drives all look identical, the different interfaces open up the possibility of performance that is not stifled by the connection between drive and chipset.
It's clearly better to have the fastest connection between the SSD's controller and the system but very few motherboards support the faster PCIe protocols. Part of the reason rests with the dearth of spare PCIe lanes available on mainstream Intel CPUs, another is a reluctance of motherboard manufacturers to dedicate up to four PCIe lanes for storage, and the final problem is a lack of compatible drives. At the time of writing, on the very popular Z97 chipset from Intel, only ASRock supports a PCIe 3.0 x4 M.2 slot, while Samsung, in the form of the SM951 SSD, is the sole supporter of the fastest M.2 interface speed.

Modern SSDs can be very fast yet are often held back by the interface. M.2 goes some way of addressing this problem by jumping on the back of the PCIe bus, clearly, but there is a better way of obtaining rocket speeds from storage.


Rather than use an intermediary connector such as M.2, one that can ride off the PCIe bus, SSD makers have realised it makes sense to launch models that plug directly into a motherboard's PCIe expansion slots. Connecting to the chipset in this manner has the same effect as using the best implementation of M.2, but the advantages are obvious: most consumer motherboards have at least one spare PCIe x4/16 slot.

Intel 750 Series PCIe SSDs

The impressive Intel SSD 750 uses a PCIe 3.0 x4 interface and has NVMe support

Such SSD drives are referred to as add-in cards or PCIe HHHL and provide the optimum method of achieving the fastest storage speeds in a regular PC. These HHHL drives often look like half-height graphics cards, are equipped with a PCIe x4 connector and can be used in either the dedicated x16 slot for graphics cards or any spare x4 on the motherboard.

Expect to see read and write speeds approach, or even surpass, 1,000MB/s - a PCIe x4 connection is needed for anything above 800MB/s - while the latest drives use the new NVMe protocol to boost speeds further, reduce latency and add extra efficiency for super-fast storage.

NVMe-compatible drives, such as the Intel SSD 750 above, use the PCIe interface to the fullest. Offering peak read and write speeds of 2,600MB/s and 1,200MB/s, respectively, which is only possible through a PCIe 3.0 x4 link to the chipset, such add-in card drives set a new standard for storage speed.

Connecting to the PCIe bus and bypassing the bandwidth limitations of SATA makes implicit sense for the next generation of consumer SSDs. If you're on the lookout for wonderfully fast storage ensure that the drive is compatible with PCIe, preferably in the fastest Gen 3.0 x16 model that offers real-world speeds of up to 3,200MB/s.

Having a very fast SSD connected via SATA is akin to driving a Ferrari at 70mph. PCIe breaks the bandwidth shackles imposed by SATA, enabling SSDs to realise their full speed potential - think of that Ferrari running flat out on a closed test track. Scan Computers has a rich history of catering for the enthusiast and their cutting-edge needs. We have a wide range of M.2 or HHHL PCIe-based SSDs available immediately, and you can view our selection of Intel PCEe SSD Drives