PCIe (Peripheral Component Interconnect Express) is a high-speed interface standard used to link a computer's motherboard to external peripherals.

Most components in personal laptops, such as Ethernet devices, graphics cards, SSDs, and hard drives use PCIe as a motherboard connection.

Since the first release of PCIe 1.0, various subsequent versions have been released, including PCIe 5.0, 4.0, 3.0, and 2.0.

Among them, the variations between PCIe 4.0 and 3.0 SSDs are the most contentious.

So, if you ever need to increase the efficiency of your device, M.2 PCIe is the best option.

Differences between PCIe 3.0 and 4.0

1. Slot

A single PCIe slot can now support x16, x8, x4, x2, or x1 lanes. For example, PCIe 3.0 x4 indicates a Gen 3 expansion slot/card with four lanes.

Because each lane is a separate connection between the motherboard's PCI controller and the expansion card, the total number of lanes determines the bandwidth scaling.

A 4-lane connection, then, has double the bandwidth of a 2-lane connection.

Both PCIe 3.0 and 4.0 slots feature x1, x2, x4, x8, and x16 lane configurations, although the bandwidth throughput and transfer rate per lane is different.

A PCIe 3.0 slot, for example, features an 8 GT/s transfer rate per lane, whereas a PCIe 4.0 slot possesses a 16 GT/s transfer rate per lane.

2. Compatibility

Although PCIe 3 and 4 are forward and backward-compatible, high-speed components that use PCIe slots to connect to the motherboard operate differently depending on the size of the PCIe lane layout.

A PCIe 3.0 SSD card can be inserted into a motherboard having PCIe 4.0 slots, but the SSD will not be able to make use of the greater bandwidth of the Gen 4 slot.

Furthermore, you must ensure that the motherboard's slot has the same or more lanes than that of the expansion card you are inserting. Otherwise, your card will not be physically placed into the slot.

A PCIe 3.0 x4 SSD card, for example, can be inserted into a PCIe 4.0 x14 slot, while a PCIe 3.0 x16 card cannot be inserted into an x1, x2, x4, or x8 slot.

As a result, you need to first determine whether your PCIe 4.0 or 3.0 SSD card will fit in the motherboard's lane layouts.

3. Speed/Performance

When selecting a PCIe SSD, you should also consider transfer speed. PCIe 4.0 has a data transfer rate of 16 GT/s, however, PCIe 3.0 has 8 GT/s.

As a result, PCIe 4.0 is at twice the pace of PCIe 3.0. Furthermore, the bandwidths of different lane designs differ.

PCIe 4.0 unidirectional bandwidth varies from 2 GB/s (x1 lane) - 32 GB/s (x16 lane), whereas PCIe 3.0 unidirectional bandwidth varies from 1 GB/s (x1 lane) - 16 GB/s (x16 lane).

In other words, each PCIe 4.0 lane is twice the bandwidth of a PCIe 3.0 lane.

PCIe 3.0 and 4.0 and their compatibility with M.2 PCIe

M.2 PCIe SSDs support both PCIe 3.0 and 4.0 but PCIe 4 is more efficient and better than PCIe 3.

Those that support the newest Gen 4 specifications are nearly two times faster than their predecessors.

Though Gen 3 SSDs have read and write rates of roughly 3,500 MB/s, Gen 4 SSDs have read and write rates of over 7,000 MB/s.

However, those who use it regularly will probably never notice this performance increase.

Gen 3 SSDs are lightning-fast for almost any workload. Most people will not notice a variation in load times of a few milliseconds.

Partner with us for premium M.2 PCIe to upgrade the performance of your device

PCIe 3.0 and 4.0 are compatible with M.2 PCIe, providing optimal performance throughout use. Please contact us as soon as possible for the best products.