Detailed explanation of various slots on the motherboard: SATA, PCIe and M.2

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If you want to upgrade your graphics card or SSD, you need to know the motherboard interfaces on your computer that support graphics cards and SSDs. This will help you choose the appropriate hardware that can maximize performance.

Detailed explanation of various slots on the motherboard: SATA, PCIe and M.2

Commonly used interfaces for SSD and graphics cards are SATA and PCI Express. SATA is considered an outdated technology but is still very common when it comes to upgrading hard drives, especially in many older laptops. On the contrary, the PCIe interface is very powerful, not only replacing SATA, but also having different versions.

SATA : The long-standing standard hard drive interface    

Detailed explanation of various slots on the motherboard: SATA, PCIe and M.2

The SATA (Serial Advanced Technology Attachment) interface has long been the standard connection for mass storage and removable storage drives such as CDs and DVDs.

Nowadays, SSDs use SATA less and less, and are gradually replaced by PCI Express. HDDs still mainly use SATA interfaces.

The current version is SATA 6G, also known as SATA-III or SATA-600. The theoretical transfer rate is 600MB/s, hence the name SATA-600.

Sequential writes of over 500MB/s and read speeds of approximately 550MB/s can be achieved using SATA SSDs. SATA 6G is backward compatible, but SATA-I and SATA-II are rarely used now.

eSATA : SATA interface for external hard drives    

Detailed explanation of various slots on the motherboard: SATA, PCIe and M.2

eSATA (external SATA) leads out the internal interface to connect the external hard disk. The transfer rate of eSATA is the same as SATA. eSATA cannot transmit power and typically requires power via a separate power adapter.

For this reason, it is common to combine eSATA with USB in a single connection, with the connected eSATA device receiving power through the USB part and data being transferred through the eSATA part.    

eSATA is rarely seen on laptops anymore and has been replaced by USB. Only occasionally used for network storage devices (NAS) to connect external hard drives.

SATAe : an upgraded version of SATA 6G that is not widely used

Detailed explanation of various slots on the motherboard: SATA, PCIe and M.2

SATAe, or SATA Express , was originally regarded as an upgraded version of SATA 6G, but it failed to gain widespread adoption.

The concept is to use PCI Express instead of SATA for the physical transfer of the SSD. By bundling two SATA ports and transporting them over PCI Express, original SATA 6G speeds are doubled, creating a PCIe x2 connection that equates to 1,000MB/s under PCIe 2.0 and 1,000MB/s under PCIe 3.0 2,000MB/s.

To maintain SATAe backward compatibility, the interface has a three-part design. Two SATA hard drives can be connected and the transfer speed will be reduced to SATA speed. In addition to the two SATA sockets, the connector also has areas for PCIe clock signals and power supplies.    

However, corresponding flash drives never gained popularity, primarily due to the limitation of two PCIe lanes. In comparison, M.2 SSD drives utilize up to four PCIe lanes. Under PCIe 3.0, they can reach speeds close to 4,000MB/s.       

PCIe : A common interface for many computer components

PCIe ( Peripheral Component Interconnect Express ) connects components directly to the processor or I/O hub.

PCIe uses a structure called lanes, which can increase the data transfer rate through bundling. The higher the PCIe version number, the higher the transfer speed per lane.

The number of lanes required depends on the individual components and is represented by a number after the letter “x”, which also indicates the size of the different slots on the motherboard, such as x1, x4, x8 or x16. The x1 slot is very short, while the x16 slot is relatively long.

PCIe transfer speed : This is a combination of PCIe version and lane number. For example, under PCIe 3.0, the rate of each channel is 8GT/s (one billion transfers per second), which is equivalent to a bandwidth of 970MB/s per channel. Under PCIe 3.0 x4, it can theoretically reach 3.9GB/s speed.

The actual available data transfer rate will be lower because, in addition to pure data transfer, the transfer protocol also consumes bandwidth.          

PEG slot – extra slot for graphics card    

Detailed explanation of various slots on the motherboard: SATA, PCIe and M.2

PEG (PCI Express for Graphics) is a dedicated slot on the motherboard for graphics cards. It is equipped with up to 16 PCIe lanes and can provide a maximum of 75 watts of power. By comparison, other PCIe slots are limited to a maximum of 25 watts, or even just 10 watts.

Since power from the socket alone is usually not enough to power the graphics card, it is possible to increase power to the GPU by making additional connections to the power supply. A 6-pin connector provides an additional 75 watts, while a 6- to 8-pin cable provides up to an additional 150 watts.

For high-performance graphics cards aimed at gamers, multiple 8-pin cables may also be needed to meet power needs. For example: Since the Geforce RTX 3000 series, Nvidia has opted for a 12-pin power connector with up to 600 watts of additional power.

PCIe slot and lane assignments

PCI Express is very flexible and backwards compatible with every generation. Therefore, you can also use a PCIe 4.0 graphics card on a PCIe 3.0 motherboard, but the data transfer performance will be reduced.

You can even use the slots flexibly, such that an x1 card can also work in an x4 slot. But the motherboard architecture must be taken into consideration, as not every slot will automatically connect to a full channel.

For example, if there are two PEG slots and one is occupied by a graphics card that requires 16 channels, this means that there are no channels available in the second slot.    

If the graphics card is inserted into the second slot, the eight channels can also be automatically switched to the second slot. There are many connection methods, so study the motherboard manual carefully.

Compact solid-state drive (SSD) using PCIe via M.2 slot

Detailed explanation of various slots on the motherboard: SATA, PCIe and M.2

M.2 is an interface specification developed from Next Generation Form Factor (NGFF). This compact slot allows connection of up to four lanes of small modules via PCIe.

Because it easily overcomes SATA’s limitations in transfer speeds, M.2 is widely used in internal SSDs such as particularly thin laptops.

The slot determines the size of the M.2 SSD. On most motherboards, you’ll see an M.2 slot labeled 2280, which means it’s 22mm wide and 80mm long. This specification is important as it not only determines the size of the appropriate card, but also the location of the set screws. Other sizes include 2230, 2242 or 22110, which differ only in length.

M.2 slot SSDs utilize the NVMe transmission protocol, so they are also called NVMe SSDs.    

Special features of M.2 SSDs : M.2 slots are not only suitable for SSDs with PCIe controllers, the slot combination can also be used for SATA SSDs. Once the M.2 slot is used by a SATA SSD, it switches from PCIe to SATA.

Pure SATA M.2 slots can still be found even on older laptop motherboards or cases used for external SSDs.

Detailed explanation of various slots on the motherboard: SATA, PCIe and M.2

The M.2 SSD used can be identified by a cutout (called a key) at the module connection, ensuring that only compatible cards can be inserted into the slot. M.2 SSDs using PCIe (x2 and x4) can be identified by the cutout Key M, with two cutouts on the right and left (Key B+M) usually only support PCIe x2 or SATA.    

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