An overview of the new M.2 piloting interface
Computers are getting smaller and smaller, as are hardware components like storage drives. The introduction of solid-state hard drives made it possible to design thinner models like Ultrabooks, but this clashed with the industry standard SATA interface.
The mSATA interface was designed to create a thin profile card that could interact with the SATA interface. A new problem arose when SATA 3.0 standards limited the performance of SSDs. A new form of compact card interface had to be developed to correct these problems.
Originally called NGFF (Next Generation Form Factor), the new interface has been standardized to an M.2 drive interface according to the specifications of SATA version 3.2.
While size is a factor in the development of an interface, reader speed is just as critical. The SATA 3.0 specifications limited the actual bandwidth of an SSD over the drive interface to around 600MB / s, which many drives have achieved. The SATA 3.2 specification introduced a new mixed approach for the M.2 interface, as was the case with SATA Express.
In essence, a new M.2 card can use the existing SATA 3.0 specifications and be limited to 600MB / s. It can also use the PCI-Express standard, which offers 1Gb / s bandwidth by PCI- standards. Current Express 3.0. This 1 Gb / s speed is for a single PCI-Express lane, but multiple lanes can be used. According to the M.2 SSD specification, up to four lanes can be used. Using two lanes would theoretically achieve 2.0 Gb / s, while four lanes would provide up to 4.0 Gb / s.
With the eventual release of PCI-Express 4.0, these speeds would effectively be doubled. The release of PCI-Express 5.0 in 2017 saw an increase in bandwidth to 32 GT / s, with 63 GB / s in a 16-lane configuration. PCI-Express version 6.0 (2019) saw another doubling of the bandwidth to 64 GT / s, allowing 126 GB / s in each direction.
Not all systems achieve these speeds. The M.2 reader and the interface must be configured in the same mode. The M.2 interface uses either the old SATA mode or the newer PCI-Express modes. The reader selects which one to use.
For example, an M.2 drive designed with the older SATA mode is limited to 600MB / s. While the M.2 drive is PCI-Express compatible up to four lanes (x4), the computer doesn’t uses only two (x2). This results in maximum speeds of 2.0 Gb / s. To get the highest speed possible, check what the drive and the computer or motherboard support.
Smaller and larger sizes
One of the goals of the M.2 drive design was to reduce the overall size of the storage device. This goal has been achieved in several ways. First of all, the cards were made narrower than in the previous mSATA form factor. M.2 cards are 22mm wide, compared to 30mm for mSATA. The cards are also shorter in length, at 30mm long, compared to the 50mm of mSATA. The difference is that M.2 cards support longer lengths of up to 110mm. This means that these disks can be larger, which provides more space for the chips and, therefore, higher capacities.
In addition to the length and width of the cards, there is an option for single or double sided M.2 cards. Single-sided cards offer a slim profile and are useful for ultra-thin laptops. A double-sided card allows twice as many chips to be installed on an M.2 card, increasing storage capacity. This is useful for compact desktop applications where space is not as critical.
The problem is, you need to know what type of M.2 connector is on the computer, in addition to the space for the length of the card. Most laptops only use a single-sided connector, which means laptops cannot use double-sided M.2 cards.
For over ten years, SATA has made storage a plug-and-play operation. This is due to the simplicity of the interface and the AHCI (Advanced Host Controller Interface) operating structure.
AHCI is the way computers communicate instructions with storage devices. It is integrated into all modern operating systems and does not require the installation of additional drivers when adding new drives.
The AHCI was developed at a time when hard drives had a limited ability to process instructions due to the physical nature of read heads and platters. A single queue of 32 orders was sufficient. The problem is that today’s hard drives do a lot more, but are still limited by the AHCI drivers.
The NVMe (Non-Volatile Memory Express) command structure and drivers have been developed to eliminate this bottleneck and improve performance. Rather than using a single command queue, it allows up to 65,536 command queues to be set up, with a maximum of 65,536 commands per queue. This allows more parallel processing of storage read and write requests, which increases performance over the AHCI command structure.
While this is a good thing, there is a small problem. AHCI is built into all modern operating systems, but NVMe is not. Drivers should be installed in addition to existing operating systems to get the most out of the drives. This is a problem for many older operating systems.
The M.2 drive specification allows either of two modes. This facilitates the adoption of the new interface with existing computers and technologies. As support for the NVMe command structure improves, the same drives can be used with this new command mode. However, switching between the two modes requires reformatting the drives.
Improved energy consumption
A mobile computer has a limited operating time depending on the size of its batteries and the power consumed by its components. Solid state drives reduce the power consumption of the storage component, but there is room for improvement.
As the M.2 SSD interface is part of the SATA 3.2 specification, it includes other features than the interface. These include a new feature called DevSleep. As more and more systems are designed to go into sleep mode when they are shut down or turned off, rather than shutting down completely, the battery is constantly strained to keep certain data active for quick recovery when the device is powered down. wake up. DevSleep reduces the amount of energy used by devices by creating a new lower power state. This should extend the operating time of computers that are put into sleep mode.
The M.2 interface is an advancement in computer storage and performance. Computers should use the PCI-Express bus for the best performance. Otherwise, it works the same as any existing SATA 3.0 drive. It doesn’t seem like a big deal, but it’s a problem for most of the early motherboards that used this feature.
SSDs provide the best experience when used as root drive or bootable drive. The problem is that existing Windows software has a problem with many drives booting from the PCI-Express bus rather than SATA. This means that an M.2 drive using the PCI-Express bus will not be the primary drive on which the operating system or programs are installed. The result is a fast data drive but not the boot drive.
Not all computers and operating systems are affected by this problem. For example, Apple developed macOS (or OS X) to use the PCI-Express bus for root partitions. Indeed, Apple upgraded its SSDs to PCI-Express in the 2013 MacBook Air, before the M.2 specifications were finalized. Microsoft has updated Windows 10 to support the new PCI-Express and NVMe drives. Older versions of Windows may also work if the hardware is supported and if external drivers are installed.
Another area of concern, especially for desktop motherboards, is how the M.2 interface is connected to the rest of the computer system. There is a limited number of PCI-Express lanes between the processor and the rest of the computer. To use a PCI-Express compatible M.2 card slot, the motherboard manufacturer must remove these PCI-Express lanes from other system components.
A major concern is how these PCI-Express lanes are distributed among devices on the cards. For example, some manufacturers share PCI-Express lanes with SATA ports. Thus, using the M.2 drive slot can consume up to four SATA slots. In other cases, M.2 may share these lanes with other PCI-Express expansion slots.
Check how the card is designed so that M.2 does not interfere with the potential use of other SATA hard drives, DVD drives, Blu-ray drives, or other expansion cards.