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Difficulty: HardStorage Devices and Interfaces

A technician is installing replacement solid-state storage into a desktop system. The motherboard technical manual specifies that M.2 Slot 1 is M-key only and connected directly to four PCIe 4.0 lanes, while M.2 Slot 2 is B-key only and wired through the SATA controller and two PCIe 3.0 lanes. Which of the following statements correctly describe the compatibility and performance characteristics of these slots? (Select TWO.)

  1. An M.2 NVMe SSD with a single M-key notch can be installed in Slot 1, but it will be physically blocked from fully inserting into Slot 2.Answer
  2. An M.2 SATA SSD installed in Slot 2 will be capped at standard SATA III maximum transfer rates of 6 Gbps despite being in an M.2 form factor.Answer
  3. C
    An M.2 SATA SSD installed in Slot 1 will automatically upgrade to NVMe throughput speeds because the slot connects directly to PCIe lanes.
  4. D
    Installing an M.2 drive with a dual B&M-key edge connector into Slot 2 guarantees PCIe 3.0 x2 NVMe speed performance.

Answer

An M.2 NVMe SSD with an M-key notch will physically fit into Slot 1 but not Slot 2, and an M.2 SATA SSD in Slot 2 will remain limited to 6 Gbps SATA III speeds.
Physical M-key drive connectors prevent mechanical insertion into B-key slots. Furthermore, M.2 drives utilizing the SATA protocol remain constrained by SATA III 6 Gbps speed limitations regardless of the M.2 connector interface.

Step-by-Step Solution

1
Analyze physical keying constraints for M.2 SSD slots and connectors.
M-key drives have a notch at pins 59–66 and only fit into M-key sockets. B-key slots have a ridge at pins 12–19, physically blocking M-key-only NVMe drives.
Physical keying prevents users from inserting drives into slots that do not supply the required electrical signals or bus interfaces.
2
Determine protocol limits vs physical form factor capabilities.
An M.2 SATA drive utilizes the SATA III bus standard, which is capped at a maximum throughput of 6 Gbps (roughly 550-600 MB/s), regardless of using an M.2 slot.
Form factor (M.2) does not dictate speed; speed is defined by the underlying bus protocol (SATA vs NVMe/PCIe).

Key Concept

Distinction between M.2 physical keying (B-Key vs M-Key) and bus protocols (SATA vs PCIe/NVMe)
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Topics

Storage Devices and Interfaces

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