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Difficulty: MediumStorage Devices and Interfaces

A technician is upgrading a laptop system by installing a secondary 1 TB M.2 solid-state drive (SSD). The system documentation indicates that the available onboard M.2 slot is designated as B-key only and operates exclusively on the SATA bus. The technician purchases an M.2 M-key PCIe NVMe SSD for the installation. Which of the following will occur when the technician attempts to install this drive?

  1. The M-key NVMe drive will physically fail to fit into the B-key slot due to mechanical keying notch incompatibility.Answer
  2. B
    The drive will physically fit into the slot and operate normally, but its throughput will be bottlenecked to SATA III transfer speeds.
  3. C
    The drive will fit into the socket but will fail detection until the system BIOS controller mode is toggled from AHCI to RAID.
  4. D
    The drive will fit and function at full PCIe speeds by utilizing the motherboard's onboard SATA controller channels.

Answer

The M-key NVMe drive will physically fail to fit into the B-key slot due to mechanical keying notch incompatibility.
M.2 form factor specifications use mechanical keying notches to prevent users from installing incompatible devices. A B-key slot has pins 12–19 missing/notched and supports SATA or PCIe x2 interfaces, whereas an M-key SSD has pins 59–66 notched for PCIe x4 NVMe operation. Therefore, an M-key NVMe SSD physically cannot be inserted into a B-key slot.

Step-by-Step Solution

1
Compare the mechanical keying of the target slot against the keying of the replacement drive.
The motherboard slot is B-keyed (notch at pins 12–19), while the replacement drive is M-keyed (notch at pins 59–66).
M.2 mechanical keying prevents inserting incompatible bus standards into designated motherboard slots.
2
Evaluate physical insertion compatibility.
Because the keying notches do not align, the drive cannot be physically inserted into the connector.
Keying prevents hardware damage caused by applying incorrect bus voltage or interface pins.

Key Concept

M.2 Form Factor Keying and Interface Compatibility
Estimated Time:1m 0s
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Topics

Storage Devices and Interfaces

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