220-1101 Hardware Practice Question
A technician builds a PC with a CPU that supports PCIe 4.0, a motherboard with PCIe 4.0-capable slots, and a PCIe 4.0 GPU. After installation, the GPU is running at PCIe 3.0 speeds according to GPU-Z. The technician has updated the motherboard BIOS to the latest version and installed the latest chipset drivers. Which of the following is the MOST likely cause of the GPU not running at PCIe 4.0?
⚠ Common exam trap
Test-takers frequently assume all PCIe slots on a motherboard support the same generation, when in reality only the primary x16 slot (connected to the CPU) may support PCIe 4.0, while secondary slots are often limited to PCIe 3.0 or 2.0.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A. The GPU is installed in a secondary PCIe slot that is limited to PCIe 3.0
The most likely cause is that the GPU is installed in a secondary PCIe slot that is limited to PCIe 3.0. Even though the motherboard supports PCIe 4.0, not all slots on the board are necessarily wired for PCIe 4.0; secondary slots often run at PCIe 3.0 or lower due to chipset lane limitations. Installing the GPU in the primary (top) x16 slot, which is directly connected to the CPU, would allow PCIe 4.0 speeds.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A. The GPU is installed in a secondary PCIe slot that is limited to PCIe 3.0
Why this is correct
The GPU is installed in a secondary PCIe slot that is limited to PCIe 3.0. Secondary x16 slots are often routed through the chipset rather than the CPU, and many chipsets still provide only PCIe 3.0 lanes, even when the CPU supports PCIe 4.0. PCIe link speed is negotiated between the GPU and the slot, so the card will drop to PCIe 3.0 to match the slot's maximum capability. This is a hardware limitation of the motherboard, not a GPU or firmware issue.
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B. The GPU firmware (vBIOS) is outdated
Why it's wrong here
An outdated vBIOS can cause stability, display, or feature compatibility problems, but it does not normally force a PCIe link to operate at a lower generation. The negotiated PCIe speed is determined by the electrical and protocol capabilities of the GPU, slot, and CPU at power-on, which are set in hardware registers, not in the GPU's firmware. A vBIOS update might add compatibility fixes, but it cannot make a physically PCIe 3.0-connected slot run at PCIe 4.0. Therefore, a vBIOS update would not resolve a consistently lower link speed.
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C. The power supply unit does not provide enough wattage
Why it's wrong here
Insufficient power supply wattage can cause system shutdowns, crashes, black screens, or failure to boot, but it does not reduce the PCIe link speed. Link speed is negotiated during the training sequence between the GPU and the motherboard slot, independent of power delivery levels. If the PSU were too weak, the GPU would likely fail under load or cause instability, not simply negotiate a slower link. A stable but slower PCIe link points to slot capability, not wattage.
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D. The GPU is not fully seated in the PCIe slot
Why it's wrong here
Improper GPU seating in the PCIe slot would typically produce no display output, a loose connection, or an intermittent error at boot, not a stable but slower link speed. When a card is not fully seated, some contacts may not connect, causing training failures or lane reductions, but a consistent downgrade to PCIe 3.0 from a PCIe 4.0 slot would be unusual. A properly seated PCIe 4.0 GPU in a PCIe 4.0 slot will negotiate at 4.0 regardless of clamping torque. Thus, a loose card is not a plausible explanation for a clean reduction to PCIe 3.0.
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