220-1201 Practice Question: A technician is installing a new power supply in…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  The PSU will automatically combine the rails to provide 40A to the GPU.

  Why it's wrong here

  Multi-rail power supplies are designed with independent 12V rails, each having its own Overcurrent Protection (OCP) circuit and current limit, typically around 20A. They do not automatically combine their output to supply a single component with higher amperage. To achieve a combined output, a specific PSU design would be required, often seen in single-rail PSUs or specialized multi-rail units that explicitly state rail-combining capabilities, which is not the default behavior.

• ✓

  The GPU may cause overcurrent protection to trip on one rail, causing shutdowns.

  Why this is correct

  High-power Graphics Processing Units (GPUs) can draw significant current, often exceeding 20A under full load. In a multi-rail power supply, if a GPU's power connectors are all drawing from a single 12V rail, and its current demand surpasses that rail's Overcurrent Protection (OCP) limit (e.g., 20A), the OCP will trip. This safety mechanism will cut power to that specific rail, leading to an immediate system shutdown or instability to prevent damage.

• ✗

  The PSU will deliver stable power as long as the total wattage is sufficient.

  Why it's wrong here

  While total wattage capacity is crucial for overall system power delivery, it is insufficient alone for multi-rail power supplies. Each individual 12V rail has a specific current limit, typically 20A, enforced by its Overcurrent Protection (OCP). Even if the PSU's combined wattage rating is ample, exceeding the current limit on any single rail, such as by a high-power GPU, will trigger OCP and cause system instability or shutdowns, regardless of the remaining available wattage on other rails.

• ✗

  The GPU will automatically draw power from both rails equally.

  Why it's wrong here

  A Graphics Processing Unit (GPU) is a passive component in terms of power distribution; it draws power from the specific PCIe power connectors it is plugged into. The GPU itself does not actively manage or balance the load across different 12V rails. The distribution of power across rails is determined by how the PSU's internal wiring assigns specific physical connectors to particular 12V rails. Therefore, if both PCIe power cables are wired to the same 12V rail, the GPU will draw all its power from that single rail, potentially overloading it.

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