M.2 SATA and M.2 NVMe SSDs come in the same form factor. The M.2 connectors might be different but an NVMe port would support the M.2 SATA SSD physically. However, whether the system supports the SATA drive or not will depend solely on how the motherboard is designed. Some M.2 NVMe ports are designed to handle both the NVMe and SATA drives while some would be dedicated only to the NVMe drives.
So, the compatibility of your M.2 SATA drive on an M.2 NVMe slot would be based on how your motherboard is designed. Let’s look at two motherboards as an example. I own these motherboards and have used different SSDs on different slots to confirm the compatibility.
Using M.2 SATA SSD in M.2 NVMe Port
Things determining an M.2 port’s compatibility
The first and obvious thing is the port’s physical structure i.e. its keying. Different keying configurations are as follows:
B-key: Supports SATA and PCIe x2.
M-key: Supports PCIe x4 (typically NVMe).
B+M key: Can support both SATA and PCIe but is limited by the host slot.
The second most important thing is how that port is connected to the CPU. If it has a direct connection to the CPU, it would most probably support the NVMe SSDs only. However, some processors support both PCIe and NVMe drives to work directly with the CPUs. The motherboard’s chipset also decides whether a port would be compatible with one type of drive or both.
The M.2 slot can be configured by the motherboard to support PCIe (NVMe), SATA, or both. The user manual specifies which protocols are supported by each M.2 slot.
M.2 NVMe drives need PCIe lanes to connect to the CPU. So, an NVMe slot will have the PCIe lanes allocated to it. The number of lanes and the generation depends on the motherboard design. Other ports will connect the SATA bus allowing only the SATA drives. Some ports are hybrid and controlled by the chipset. These ports will support both M.2 NVMe and SATA drives. When an NVMe drive is connected, it generally bypasses the chipset and connects to the CPU. In the case of M.2 SATA drives, the connection will be routed through the SATA bus and chipset.
More about Hybrid M.2 Slots
There are two possible connection scenarios for the hybrid M.2 slots. Because these slots support both types of M.2 drives, the connections are going to be different.
Direct Connection to CPU (for NVMe):
Some motherboards connect the M.2 slot directly to the CPU’s PCIe lanes when an NVMe drive is used. This allows for the highest possible data transfer speeds because the NVMe drive can communicate directly with the CPU without going through the chipset.
In this case: When using an M.2 NVMe SSD, the system would bypass the chipset and connect directly to the CPU. When you install an M.2 SATA SSD, it will switch to using the SATA bus via the chipset.
Connection via Chipset:
In other cases, the M.2 slot, whether for NVMe or SATA drives, is connected through the chipset. This means that even an NVMe drive would communicate with the CPU via the chipset. This would increase the latency and cause a little bottleneck as compared to the direct CPU connection.
Real-Life Examples
Motherboard No. 1: MSI Pro Z690-A DDR5 (PCIe 4.0)
This is my primary motherboard and it comes with 4x M.2 slots (M-Key). The primary slot which is the first and nearby slot to the CPU is dedicated just for the NVMe drives. It offers 4 PCIe 4.0 lanes to the SSDs which means no bottlenecks for the Gen 4.0 drives. This port generally offers the lowest latency and highest bandwidth to the SSDs. However, because this is a mid-range motherboard, it has one more slot dedicated just for the NVMe drives with the same amount of PCIe lanes. Both ports are handled directly by the CPU and have full access to the NVMe protocol.
Things start to look different at the 3rd M.2 slot. As you can see in the screenshot below. the third slot is controlled by the Z690 chipset. It supports the PCIe NVMe SSDs but the allocated 4 PCIe lanes are from PCIe 3.0. This will cause a serious bottleneck to the Gen 4.0 drives (around 50% bottleneck). But, this port supports the M.2 SATA SSD with the maximum bandwidth of SATA i.e. 6Gb/s. The same goes for the 4th slot, however, it has 4x PCIe 4.0 lanes instead of PCIe 3.0 lanes.
So, we can say that I can install two M.2 SATA SSDs on my M.2 NVMe SSD slots. However, two M.2 NVMe slots controlled that are directly connected to the CPU only support the M.2 NVMe drives.
Motherboard No. 2: Asus Prime A320M-K (PCIe 3.0)
Things are different for this motherboard as it is a low-end motherboard, first of all, and also has just one M.2 slot. If you look at its specifications, it supports both the M.2 NVMe and SATA drives.
I have used this motherboard with both types of drives and they work just perfectly. This port can switch to the chipset or direct CPU connection depending on the connected drive. So, the NVMe performance would not be bottlenecked by the chipset.
How to know if your M.2 NVMe slot supports the M.2 SATA SSD?
The best way is to go through the motherboard user manual and the storage specification section. If your motherboard has many M.2 ports, one or two of these ports would support both NVMe and SATA drives. You just have to check which port is your one. You can check the port location on the user manual itself or the ports will be named on the motherboard itself.
Another thing is to check if the NVMe is supported in the BIOS. Some older motherboards just allow the NVMe drives to work but don’t allow the NVMe protocol to be used as the primary OS drives. However, these motherboards are pretty rare to see.
Just don’t go with the physical compatibility only. Most M.2 slots would physically allow both NVMe and SATA drives but on the software level, they might not support different drives. So, it is best to check the motherboard user manual first. In most cases, if an M.2 slot is connected to the CPU through the chipset, it would allow the SATA M.2 SSDs.
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