SOLVED: Is PCIe Gen4 Backwards Compatible with PCIe Gen3?

In a word, yes.

In our case we had a client that wanted a large M.2 solid state drive (SSD) installed into a Dell 5550 laptop which has a PCIe gen3. The problem for us was that most current SSD’s are PCIe generation 4 and we didn’t want to be limited to only buying the older PCIe gen 3 SSDs. PCIe Gen 4 M.2 SSDs can be used on a PCIe Gen 3 system, which was good news for our client.

DIFFERENCE BETWEEN PCIe Gen 3 and PCIe Gen 4

PCIe Gen 4 can operate a double the transfer data rate of PCIe Gen 3:

GenerationYear of ReleaseData Transfer Ratex1 Lanex16 Lanes
PCIe 1.020032.5 GT/s250 MB/s4.0 GB/s
PCIe 2.020075.0 GT/s500 MB/s8.0 GB/s
PCIe 3.020108.0 GT/s1 GB/s16 GB/s
PCIe 4.0201716 GT/s2 GB/s32 GB/s
PCIe 5.0201932 GT/s4 GB/s64 GB/s
PCIe 6.0202164 GT/s8 GB/s128 GB/s

If you are working with ssds, like we are, you’re most likely looking at a device with 4 lanes. So you can take the number in the “data transfer rate” or the “x1 Lane” rates above and multiply it by 4 if you actually wanted to know the theoretical maximum that you would receive.

SPEED REDUCTION:

The PCI Express (PCIe) standard is designed to be backward compatible. This means that a PCIe Gen 4 device can operate in a PCIe Gen 3 system, but it will function at PCIe Gen 3 speeds.

In other words, if you install a PCIe Gen 4 NVMe SSD in a PCIe Gen 3 M.2 slot, the SSD will work, but it will operate at the maximum speed of the PCIe Gen 3 interface. This is because the PCIe interface will use speeds based on the lowest of the two versions for communication.

FUTURE PROOF WITH PCIe Generation 4:

It’s important to note that while the SSD will be running at PCIe Gen 3 speeds, you are unlikely to experience a significant performance impact if your device is not fully utilizing the available bandwidth. However, if you plan to upgrade your system to support PCIe Gen 4 in the future, purchasing a PCIe Gen 4 SSD now could be a good investment.


Published by
Ian Matthews

This website uses cookies.