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Difficulty: Very hardStorage Devices and Interfaces

A technician is installing storage drives into a workstation motherboard. Drive 1 is an M.2 2280 NVMe SSD featuring an M-key connector rated for PCIe 4.0 x4. Drive 2 is an M.2 2280 SSD featuring a B+M key connector utilizing the SATA III protocol (6 Gbps6\text{ Gbps}). According to the motherboard documentation:
- Socket M2_1 connects directly to CPU PCIe lanes and supports Key M (PCIe 4.0/3.0 x4 NVMe only).
- Socket M2_2 connects to the system chipset and supports Key B and Key M (PCIe 3.0 x2 or SATA III), but enabling SATA mode on M2_2 disables physical motherboard port SATA_5.

Which of the following statements regarding physical keying compatibility, protocol routing, and system resource allocation for this configuration are correct? (Select TWO.)

  1. Installing Drive 1 in Socket M2_1 allows it to operate at its full rated PCIe 4.0 x4 bandwidth.Answer
  2. Installing Drive 2 in Socket M2_2 will function correctly using SATA protocol, but motherboard port SATA_5 will become unavailable.Answer
  3. C
    Drive 2 can be installed in Socket M2_1 and will operate at PCIe 3.0 speeds because M-key sockets automatically adapt SATA protocol signaling to NVMe.
  4. D
    Drive 1 can be installed in Socket M2_2 and will operate at PCIe 4.0 x4 speeds without throughput restriction.

Answer

Drive 1 operates at full PCIe 4.0 x4 bandwidth in Socket M2_1, and Drive 2 functions in Socket M2_2 under SATA mode while disabling physical motherboard port SATA_5.
Socket M2_1 matches the M-key form factor and provides CPU-direct PCIe 4.0 x4 lanes required for full speed on Drive 1. Socket M2_2 supports B+M keying and SATA bus routing for Drive 2, though activating SATA mode on this slot disables physical port SATA_5 due to shared chipset resources.

Step-by-Step Solution

1
Analyze Drive 1 requirements against Socket M2_1 specifications.
Drive 1 requires M-keying and PCIe 4.0 x4 NVMe support. Socket M2_1 provides CPU-direct PCIe 4.0 x4 lanes with an M-key connector, ensuring maximum performance without lane sharing.
Matching NVMe protocol and physical pinouts with direct CPU lanes yields full theoretical throughput.
2
Analyze Drive 2 requirements against Socket M2_2 specifications.
Drive 2 uses a B+M key and SATA protocol (6 Gbps6\text{ Gbps}). Socket M2_2 supports B+M physical keying and SATA protocol bus routing. However, chipset multiplexing disables physical port SATA_5.
M.2 SATA slots frequently share host controller channels with legacy SATA ports on the motherboard.
3
Evaluate potential cross-installation errors for both slots.
Socket M2_1 does not support SATA mode (NVMe only), making Drive 2 non-functional in M2_1. Socket M2_2 is limited to PCIe 3.0 x2, which would restrict Drive 1's speed.
M.2 physical slots are tied to specific controller logic and lane counts; they cannot adapt protocols or expand lane width.

Key Concept

M.2 Slot Keying, NVMe vs SATA Protocols, and Motherboard Lane Sharing
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Topics

Storage Devices and Interfaces

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