This connector supplies additional +12 V power to a PCI Express graphics card. The x16 slot delivers at most 75 W and the 6-pin auxiliary connector adds another 75 W, but many cards need more, so an 8-pin version was introduced with the PCI Express 2.0 specification (released January 2007). The 8-pin connector provides up to 150 W of +12 V. It carries three +12 V conductors, three returns and two sense pins; the card reads the sense pins to tell whether a 6-pin (75 W) or 8-pin (150 W) plug is attached. These cables are commonly called “PEG” cables, where “PEG” stands for PCI Express Graphics.
8 pin PCIe power connector at the cable.
6+2 pin PCIe power connector at the cable.
| Pin | Name | Color | Description |
|---|---|---|---|
| 1 | 12V | yellow | +12 V |
| 2 | 12V | yellow | +12 V |
| 3 | 12V | yellow | +12 V |
| 4 | Sense1 | black | Sense (grounded by both 6-pin and 8-pin plugs) |
| 5 | GND | black | Ground / return |
| 6 | Sense0 | black | Sense (grounded only by the 8-pin plug) |
| 7 | GND | black | Ground / return |
| 8 | GND | black | Ground / return |
Notes
- 6-pin vs 8-pin detection. The header has two sense pins (pins 4 and 6). An 8-pin (2×4) plug grounds both, so the card may draw up to 150 W; a 6-pin (2×3) plug grounds only one, limiting the card to 75 W; with no plug attached, both float. A sense pin is grounded in the power supply, or jumpered to an adjacent return inside the connector.
- 6+2 design. A “6+2” cable has a 6-pin body with a detachable 2-pin section: joined, it forms a full 8-pin plug (grounding both sense pins, so 150 W); split, the 6-pin part feeds a 6-pin socket. One PSU cable therefore serves either socket.
- Power and current. The 8-pin connector supplies 150 W and the 6-pin 75 W, both +12 V only; the slot adds a further 75 W. Each 8-pin contact is rated 7.0 A maximum at +12 V (the 6-pin is rated 8.0 A). The connector is built on the Molex Mini-Fit Jr. series.
- Keying. The housings are polarised so the plug mates only one way, and the 8-pin housing differs from the 6-pin so an 8-pin plug will not seat in a 6-pin-only socket; the 6+2 split provides backward compatibility.
Signals
- +12V — main supplemental power rail (pins 1–3); the only voltage the connector carries.
- GND — power return (pins 5, 7 and 8).
- Sense1 — pin 4; grounded by both 6-pin and 8-pin plugs.
- Sense0 — pin 6; grounded only by an 8-pin plug. Both sense pins grounded signals 150 W capability.
References
- Intel ATX Version 3.0 Multi Rail Desktop Platform Power Supply Design Guide — PCIe add-in card connectors — 8-pin/6-pin pin-out, the sense decoding (75 W vs 150 W) and per-contact current ratings.
- PCI Express Card Electromechanical (CEM) Specification, Revision 2.0 (PCI-SIG) — the 75 W slot limit and the 150 W supplemental-power model.