Understanding GPU and CPU Power Cable Ratings

This short guide explains power ratings for PC power cables, with a focus on:

• GPU power cables
  (PCIe 6+2-pin and 12V-2×6 / 12VHPWR)
• CPU power cables
  (EPS 4+4-pin)

There is a common belief that “an 8-pin PCIe cable can only deliver 150 W.”
This statement is not entirely correct.

Where the “150 W” Number Comes From

In the PCIe context, 150 W is not the physical limit of the cable.
Instead, it is the maximum power a GPU is allowed to draw from one auxiliary PCIe connector, as defined by the ATX standard.

According to the ATX Version 3 Multi-Rail Desktop Platform Power Supply Design Guide, under PCI-Express (PCIe) Add-in Card Connectors:

• PCIe 6-pin (2×3):
  “A 2×3 connector is plugged into the card. The card can only draw up to 75 W from the auxiliary power connection.”
• PCIe 6+2-pin (2×4):
  “A 2×4 connector is plugged into the card. The card can draw up to 150 W from the auxiliary power connector.”

These limits apply to device power consumption (the GPU) —not to the actual current-carrying capability of the cable itself.

So What Determines a Cable’s Real Power Rating?

The power-handling capability of a cable depends on the entire material system, not a single component.
There are three key factors:

1. Terminal current rating
2. Wire (conductor) current rating
3. Electrical resistance

Material Ratings Used in Our Cables

Based on the materials we use, the summarized ratings are shown below:

• * 9.2 A is based on ATX Version 3.1 specification
• ** 10 A based on 2×4 terminal application
• *** Actual wire rating depends on insulation type, ambient temperature, and installation conditions
• (12 A is used as a conservative value)

Why Connectors Melt — Not the Wires

From the table above, you can see that:
– Terminal current rating is lower than wire current rating
– This makes the terminal the bottleneck, not the cable conductor

This explains why melting incidents almost always occur at the connector housing, where the terminals are located —
not along the cable itself.

Ideal (Theoretical) Power Rating Scenarios

Under ideal conditions (no resistance loss, no voltage drop, no temperature increase), power capacity can be estimated as follows:

What This Means for GPUs and PSUs

From these calculations, it becomes clear that:

• – A cable’s physical power capacity can exceed the device’s standardized power limit
• – Even though a GPU is restricted to drawing 150 W from one PCIe 8-pin port, the cable itself can safely carry more power

The same logic applies on the PSU side, especially with single-rail power supplies:

• – All 12 V outputs come from the same rail
• – A single PCIe 8-pin port on the PSU can theoretically deliver up to ~300 W, depending on:
  • PSU design
  • PSU quality
  • Overall system load

Key Takeaway

Power limits defined by standards apply to devices — not to the physical capability of the cable itself.

Cable safety and performance depend on:
– Proper wire gauge
– High-quality terminals
– Correct crimping
– Good connector design

This is why cable quality matters, and why poorly made or low-spec cables can be dangerous even if they “look” the same.

Additional References

• – An 8-pin PCIe supports a lot more than 150 W — Jon Gerow
• – PCIe Cables: How much power does your GPU really need? — YouTube
• – Why 6-pin PCIe connectors can deliver more than 150 W — YouTube
• – Don’t Use Cheap Cables: Dangerous Construction & False Wire Gauge — YouTube
• – Intel ATX 3.0 Design Guide (Rev 2.1a, November 2023)