Power cables and connectors

Whether you are a seasoned veteran or a newcomer to the the server system building it is essential to understand the various power cables and connectors required to safely power PCIe computing units such as GPU.

So we made an summary to ensure that the system runs smoothly without any crashes, and will also prevent potential disasters like electrical fires or damaged hardware.

Different Types Of Gpu Power Connectors

GPU consume power from PCIe and power cables, in general, PCIe bus supports 75W of power.

Connector type	Max. Power	Idel for	Notices (Picture from cgdirector)	Notes
PCIe 6-Pin	75W	Old GPU
PCIe 6+2 or 8-Pin	150W	<300W GPU
CPU EPS-12V (EATX12V)	8pin (336W) 4pin (168W)	<300W GPU
12VHPWR (12-Volt High Power). 16-Pin (12+4-Pin)	150/300 /450/600W depending on the sideband	RTX 3000/4000 series	Designed for Gen-5/ATX 3.0 PSUs Gen-4/ATX 2.0 needs an 8-pin to 16-pin 600W 12VHPWR adapter	Power/Ground Pin Wire Size: 16 AWG Sideband Signals Pin Wire Size: 28 AWG

12V power rail characteristic

+12V Power rail	2x3 connector	2x4 connector	12V-2x6 connector
Sustained power	75W	150W	150W	300W	450W	600W
+12V range	+5%/-8%
Current (Max. RMS)	6.75A	13.5A	13.75A	27.5A	41.25A	55A

12VHPWR and sideband

The twelve power pins have a 9.2A per pin/position current rating at 30C T-rise above ambient temperature conditions at 12V, energizing all twelve contacts. This means that the pins should be able to deliver up to 1324.8W! The connector’s body must have a label or embossed “H++” characters to indicate the support of 9.2A per pin or higher. The wire thickness is 16 AWG, while the wire size is 28 AWG for the sideband signal pins.

The sideband signals SENSE0/SENSE1 definitions, which signal maximum available power available from the PSU based on the ATX v3.1 & PCI-SIG PCIe CEM Rev 5.1 specification. These updated SENSE0/SENSE1 combinations ensure that an Add-in Card may only draw power only when the power pins and the sideband pins are engaged and correctly asserted.

The SENSE0/1 setting of the 12VHPWR connector.

SENSE0 (s3)	SENSE1 (s4)	Initial Permitted Power at System Power Up	Maximum Sustained Power After Software Configuration
Ground	Ground	375W	600W
Open	Ground	225W	450W
Ground	Open	150W	300W
Short		100W	150W
Open	Open	0W	0W

NVIDIA has to change the graphics cards with the new 12V-2×6 connector to replace the open-open scenario with 0 Watt and PSU manufacturers have to short the SENSE pins for 150W max output. This is why all brands used the GND-GND setting for the total 600W

Different Types of Cable

There are two popular wire size standards, AWG (American Wire Gauge) and Metric Wire Gauges

It is important to know cable spec of your power connection to GPU or other devices to avoid potential disasters like electrical fires or damaged hardware.

18 AWG cable is widly used for GPU power cable at the time of writing this page.