Sense wires (also known as remote sense lines) in a 24-pin ATX cable are extra signal wires used by the power supply to monitor output voltages directly at the motherboard connector.

Key Functions

• Voltage Drop Compensation: Power cables have minor electrical resistance. Under heavy system loads, voltage drops slightly as it travels along the main power wires from the PSU to the motherboard.
• Real-Time Measurement: The sense wire carries zero current. It purely measures the voltage at the motherboard end of the cable.
• Active Regulation: The PSU receives this feedback and raises or lowers output voltage at its source to ensure the motherboard receives steady, precise voltage.

Wiring Layout & Pins

Sense lines are typically wired as double-crimp connections (two wires attached to a single terminal on the motherboard connector side).

Common sense wires on modern ATX specifications include:

Considerations for Custom Cables

If you assemble custom un-sleeved or custom-sleeved modular PSU cables, handling sense wires properly is critical:

1. Required vs. Optional: Some PSU architectures (like certain Corsair, Seasonic, or EVGA models) strictly require sense lines to boot or maintain system stability under load. Omitting them can cause fail-safe shutdowns or voltage fluctuations.
2. Double Crimps: On the motherboard side, you must crimp both the main power wire and its matching sense wire together into the same terminal pin.
3. Jumpered Sense Terminals: On custom short-cable builds where wire length is minimal, builders sometimes bridge/jumper the sense pin directly to its corresponding voltage pin at the PSU connector end. However, doing so prevents the PSU from detecting voltage drops along the length of the wire run.

Reference:

ATX Version 3 Multi Rail Desktop Platform Power Supply, Rev 2.1A, November 2023