Do Gen 4 SSDs Work in Gen 3 Slots? The Answer Might Surprise You!


If you’re like most people, you probably don’t give much thought to the type of SSD drive in your computer. After all, what difference does it make? If your computer can read and write data to the drive, it should work, right? Well, not exactly. There is a big difference between Gen 3 and Gen 4 SSDs, and if you try to use a Gen 4 SSD in a Gen 3 slot, you might be surprised by the results!

In summary, Yes, Gen 4 SSDs will work on Gen 3 slots because the PCIe bus is forward and backwards-compatible. But the speed of the connection will be limited by the lowest PCIe version between the device and the slot. Gen 4 SSD will work in the slot but only operate at Gen 3 speeds. So if you want to get the most out of your new SSD, ensure it’s paired with a compatible slot.

What Are the Generations Mean in PCIe?


PCIe, or Peripheral Component Interconnect Express, is a computer bus used to connect various components within a system. It is commonly used in computers to connect the motherboard to devices such as graphics cards and storage drives.

PCIe consists of a series of data lanes, each of which can carry a certain amount of data. The number of data lanes varies between different versions of PCIe, with newer versions offering more lanes and bandwidth than older versions. 

Simply Generations in PCIe refer to the different speeds at which the bus operates. The higher the generation, the faster the speed. PCIe consists of multiple “generations” which refer to different versions of the same technology. The first generation was released in 2003, followed by the second generation in 2007, the third in 2010 and the fourth in 2011 Each generation improves upon the previous one with higher speeds and better features such as faster data transfer rates and new levels of power efficiency. (reference

For example, a PCIe 4.0 bus has a maximum speed of 16 GT/s, while a PCIe 5.0 bus can operate at 32 GT/s. The earliest version of PCIe, 1.0, had a maximum speed of 2.5 GT/s.

Please refer to my blog post for in-depth knowledge about Gen4 and Gen 3 SSDs. PCIe Gen 4 vs PCIe Gen 3 SSD: Truth and Myths

What is the speed of Gen 4 NVMe in Gen 3 slot?

When a Gen 4 NVMe solid-state drive (SSD) is used in a Gen 3 slot, it will operate at Gen 3 speeds. This means that the maximum speed of the SSD will be limited to the capabilities of a Gen 3 interface. The Gen 4 SSD may still work in the Gen 3 slot, but it won’t be able to achieve its full potential speed.

NVMe SSDs that support the newest Gen 4 standards are nearly double the speed of the previous generation. The top speed for Gen 3 SSDs is around 3,500 MB/s for both read and write operations, but Gen 4 SSDs can reach speeds over 7,000 MB/s. Despite this significant increase in performance, it’s unlikely that the average user will detect this speed enhancement.

Which Motherboards Support PCIe Gen 4?

To fully utilize the PCIe 4.0 support offered by Intel’s 11th-generation processors, you must pair them with a motherboard with either the Z590 or B560 chipset. Conversely, a motherboard with the X570 chipset is necessary for AMD processors to take full advantage of PCIe 4.0 support.

Currently, many motherboards on the market come with PCIe Gen 4 support. These range from budget-friendly options to high-end models designed for gaming and content creation. However, it is important to note that due to the increased power requirements of PCIe Gen 4 devices, some motherboards may not be compatible with all of them. It’s important to check the manufacturer’s website to ensure compatibility before purchasing.

What is NVMe Gen 4.0 speed?

A single lane of PCIe 4.0 can deliver up to 16Gb/s, which is equivalent to 1,969 MB/s. Since NVMe uses four lanes, the introduction of the new PCIe 4.0 technology, in combination with the latest Ryzen 3700 CPUs and X570 Motherboards, doubles these speeds. As a result, the new theoretical limit for a PCIe 4.0 x4x NVMe is 7,880 MB/s or 63.04Gb/s.

How fast is PCIe NVMe 3.0?

Regarding NVMe drives and their performance, it’s important to understand the technical details. In theory, one lane of PCIe 3.0 provides a speed of 8Gb/s (GigaBITS/s). Since NVMe requires 4x lanes of PCIe, it adds up to 32Gb/s. However, considering real-world factors like encoding latency, heat, and other dynamics, the tested speed decreases slightly to 31.52 Gb/s.

Now, let’s talk about the conversion from Gb/s to MB/s. It’s worth noting that NVMe drives are rated in MB/s (MegaBYTES/second) rather than Gb/s. To convert the speed, we multiply our measured 31.52Gb/s (GigaBITS/s) by 125, giving us a speed of 3,940MB/s (MegaBYTES/second).

Understanding these technical aspects can help optimize the performance of NVMe drives for your specific needs.

Here is summary

  • PCIe 3.0 1x : 7.88Gb/s x 125 = 984.6MB/s
  • PCIe 3.0 2x : 15.76Gb/s x 125 = 1,970MB/s
  • PCIe 3.0 4x : 31.52Gb/s x 125 = 3,940MB/s
  • PCIe 3.0 8x : 63.04Gb/s x 125 = 7,880MB/s
  • PCIe 3.0 16x : 126.4Gb/s x 125 = 15,800MB/s

How fast is PCIe NVMe 4.0?

With the introduction of PCIe 4.0 technology in the new Ryzen 3700 CPUs and X570 Motherboards, the speeds of NVMe drives have doubled. Previously, one lane of PCIe 4.0 offered a speed of 16Gb/s (1,969 MB/s), but now, with the use of four lanes, the theoretical limit for PCIe 4.0 4x NVMe is 7,880 MB/s (63.04Gb/s). This significant improvement in speed makes these new technologies highly desirable for those seeking faster data transfer rates.

Here is a list of speeds on each PCIe 4 version

  • PCIe 4.0 1x : 15.76Gb/s x 125 = 1,970MB/s
  • PCIe 4.0 2x : 31.52Gb/s x 125 = 3,940MB/s
  • PCIe 4.0 4x : 63.04Gb/s x 125 = 7,880MB/s
  • PCIe 4.0 8x : 126.4Gb/s x 125 = 15,800MB/s
  • PCIe 4.0 16x : 252Gb/s x 125 = 31,500MB/s

Can You Install a PCIe 4.0 SSD on a PCIe 3.0 Motherboard Slot?

Even though PCIe 5.0 is the newest interface, many still use slots supporting PCIe 4.0. PCIe 4.0 is a faster version of the PCIe bus standard for connecting peripheral devices to a computer’s motherboard. PCIe 4.0 is backwards compatible with older versions of PCIe, which means that you can insert PCIe 4.0 expansion cards into PCIe 3.0 slots, and they will work.

But keep in mind that the slower speeds of PCIe 3.0 will limit data transfer rates. PCIe 4.0 is also forward compatible with newer versions of PCIe, so if you upgrade to a motherboard with PCIe 5.0 slots, your existing PCIe 4.0 cards will still work. However, to take advantage of the full speed of PCIe 5.0, you must upgrade to newer cards that support the faster speeds of the new standard.

For further clarification, look at the table below, which outlines the different generations of PCIe and their maximum data transfer rates.

x1 Bandwidthx2 Bandwidthx4 Bandwidthx8 Bandwidthx16 Bandwidth
PCIe 1.0250 MB/s500 MB/s750 MB/s2 GB/s4 GB/s
PCIe 2.0500 MB/s1000 MB/s2 GB/s4 GB/s8 GB/s
PCIe 3.01 GB/s2 GB/s4 GB/s8 GB/s16 GB/s
PCIe 4.02 GB/s4 GB/s8 GB/s16 GB/s32 GB/s
PCIe 5.04 GB/s8 GB/s16 GB/s32 GB/s63 GB/s
PCIe 6.08 GB/s16 GB/s32 GB/s63 GB/s126 GB/s

Well, this is for your knowledge. Some people ask me which CPU support PCIE 4.0. So, here is the list of those AMD and Intel CPUs which support the PCIe version.

Will NVME SSD Work in Any PCIe?

Kingston-A2000 NVME SSD
Kingston A2000 NVME SSD (Check on Amazon)

NVMe drives are the newest type of drives available on the market, and they offer a significant performance improvement over older types of drives. One of the key features of NVMe drives is that they use a PCIe bus rather than the older SATA bus. This allows for much higher data transfer speeds and lower latency. To know more about NVME SSD refer below.

NVMe drives must be connected to a motherboard with a PCIe slot to take advantage of these benefits. Most modern motherboards have at least one PCIe slot, but some older ones may not. Additionally, NVMe drives typically use four PCIe lanes, so motherboards with only one or two lanes may not be able to achieve the full performance of the drive.

However, many motherboard manufacturers now offer models with four or more lanes, which is becoming less of an issue. Overall, NVMe drives offer a significant performance boost over older types of drives, but they do require a compatible motherboard to work correctly.

Industry-standard NVMe drives use 4 PCIe lanes. This means that they can send and receive data quickly.

  • The theoretical peak bit rate you can achieve with PCIe 3.0 is 4 lanes x 16 (GT/s per lane) = 32 GT/s.
  • The theoretical peak bit rate you can achieve with PCIe 4.0 is 4 lanes x 32 (GT/s per lane) = 64GT/s.

Are PCIe Versions Backwards Compatible?

Yes. All generations of PCIe are backwards compatible. A device designed for a newer version of PCIe will usually work with an older version of the bus, though it may be limited to operating at the older version’s speed.

In rare cases, a device may not be compatible with an older version of PCIe due to changes in the signalling or other factors. However, devices designed for older versions of PCIe are almost always compatible with newer versions. As such, users upgrading their systems should not worry about compatibility issues when moving to a higher-speed PCIe bus.

For e.g. if you install PCIe 4.0 SSDs like Samsung 980 Pro (Check on Amazon), WD Black SN850, or Crucial P5 Plus on a PCIe 3.0 motherboard, they’ll work just fine. However, there will be a performance bottleneck since the maximum data transfer rate will be capped at PCIe Gen 3.

Also, PCIe versions are typically forward compatible too. In other words, a PCIe 3.0 device will usually work in a PCIe 4.0 slot and vice versa. While Gen-SSDs are usually backwards and forward compatible, I don’t recommend using a higher-gen SSD in a lower-gen slot or a slower-gen SSD on a higher-gen port. Why? Because in both cases, the SSD will be bottlenecked by the lower-speed interface. To get the best performance from your SSD, you want to match the drive’s generation with your computer’s slot generation.

How Much Slower Would a PCIe 4.0 SSD Be in a PCIe 3.0 Slot?

For example, look at Samsung’s 1 TB 980 PRO PCIe 4.0 NVMe M.2 SSD. I recommend this SSD in a heartbeat to anyone building a new PC. It’s fast, it’s reliable, and it has a great price.

Only a PCIe 4.0 x4 slot can provide a read speed of 7000 MB/s, far higher than the SATA SSD’s 500MB/s maximum read speed.

If this SSD is only placed in a port with two PCIe 4.0 lanes, its full potential will not be utilized as it would be limited to 4000 MB/s. The same goes for if it were only in a port with two PCIe 3.0 lanes–in that case, 2000 MB/s max speed could be expected.

If this SSD were in a port with only four PCIe 3.0 lanes (x4), it would be limited to 4000 MB/s.

Multiple PCIe Versions for CPU/Motherboard

Some computers can connect devices to different versions of PCI-Express lanes. For example, a computer might have both PCI-Express 2.0 and 3.0 lanes. In this case, you would need to decide which devices need the most bandwidth to decide which should be connected to the higher version PCIe lanes.

For example, if you use a graphics card that requires a lot of bandwidth, you would want to connect it to a PCI-Express 3.0 lane to get the best performance. Conversely, if you use a device that doesn’t require much bandwidth, you could connect it to a PCI-Express 2.0 lane and save some bandwidth for other devices. As always, read your motherboard’s manual to see what options are available to you.

When you’re designing a system that will rely on PCIe devices, it’s essential to remember that the speed of the connection will be based on the lowest PCIe version between the slot or port and the device.

In other words, if you have a PCIe 3.0 device connected to a PCIe 2.0 slot, the device will only operate at PCIe 2.0 speeds. This can significantly impact performance, so it’s important to ensure that all devices in your system are compatible with the highest possible PCIe version. 


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