PSU Cables & Connectors Complete Guide 2026 — ATX, EPS, PCIe, IEC C13/C19

Published March 28, 2026 · 18 min read · By Pro Disk Network Team

Every PSU cable and connector explained — ATX 24-pin, EPS 8-pin, PCIe 6+2, IEC C13/C19 server cords. Wattage ratings, pinouts, and what to buy for your build.

Topics: Power Supply, PSU, Cable, Connector, ATX, EPS

Why PSU Cables Confuse Everyone

Power supply cables are the least glamorous but most critical part of any IT build. Plug the wrong cable into the wrong port and you get no power, a fried component, or a spectacular spark. Yet most guides only cover desktop gaming builds and ignore workstation and server power systems entirely. This guide covers everything from the 24-pin ATX connector in your desktop to the C19/C20 locking cables that feed a 42U server rack through a PDU.

We work through three tiers: desktop and workstation internal connectors, rack server hot-swap power systems, and data center power distribution cables.

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PART 1: DESKTOP AND WORKSTATION INTERNAL PSU CONNECTORS

1. ATX 24-Pin Main Power Connector

Powers the motherboard. This is the single largest connector in any desktop or workstation build. It delivers 3.3V, 5V, and 12V rails to the motherboard for the chipset, RAM slots, PCIe slots, USB ports, and onboard components. Most modern PSUs ship this as a 20+4 pin configuration for backward compatibility with older 20-pin motherboards. Delivers approximately 300-400W.

Common mistake: Forcing the connector in at an angle. The clip should be on the same side as the retention tab on the motherboard header.

2. EPS12V 8-Pin (4+4) CPU Power Connector

Provides dedicated 12V power directly to the CPU voltage regulator modules on the motherboard. Without this cable, the system will not POST. Located near the top-left corner of the motherboard. Modern PSUs split this into 4+4 pin for compatibility with both 4-pin and 8-pin headers. Delivers up to 336W.

CRITICAL WARNING: Do NOT confuse the EPS 8-pin CPU cable with the PCIe 8-pin GPU cable. They look similar but the pinout is different. Plugging a PCIe cable into the CPU header can destroy your motherboard. The EPS cable has a different pin shape pattern with four square pins and four rounded pins.

3. Dual EPS 8+8 CPU Power (Workstations and HEDT)

High-end workstation motherboards for AMD Threadripper or Intel Xeon W have TWO 8-pin CPU power headers. Both must be populated. Delivers up to 672W combined. Required for CPUs with TDP above 250W like Threadripper PRO 7995WX at 350W. If your PSU only has one EPS cable, use a workstation-grade PSU rated 850W or higher with dual native EPS outputs.

4. PCIe 6-Pin GPU Power Connector

Provides supplemental 12V power to graphics cards drawing more than the 75W available from the PCIe slot. Delivers 75W per connector. Three pins carry 12V and three are ground. Used by older and mid-range GPUs like NVIDIA GTX 1650 Super and AMD RX 6600.

5. PCIe 8-Pin (6+2) GPU Power Connector

Delivers 150W per connector for higher-end graphics cards. Often shipped as a 6+2 configuration to fit both 6-pin and 8-pin GPU headers. Used by NVIDIA RTX 3070, AMD RX 7800 XT, and most modern mid-to-high-end GPUs. Many high-end cards require two or three 8-pin connectors for 300-450W total GPU power.

6. 12VHPWR and 12V-2x6 16-Pin Connector (ATX 3.0/3.1)

The newest power connector standard. A single cable delivers up to 600W, replacing multiple 8-pin cables. The 12V-2x6 version (ATX 3.1) fixes the melting issues from the original 12VHPWR design with a more secure locking mechanism. Used by NVIDIA RTX 4070 and above, RTX 5090, RTX 5080. Always plug straight in and fully seat the connector. Use official adapters only.

7. SATA Power Connector (15-Pin)

Powers SATA devices including 2.5-inch and 3.5-inch hard drives, SSDs, and optical drives. The L-shaped 15-pin connector prevents backward insertion. Delivers up to 54W per connector. SATA power cables are daisy-chained with 3 to 4 connectors per cable. Never use Molex-to-SATA adapters as they are a known fire hazard. Always use native SATA power cables from your PSU.

8. Molex 4-Pin Peripheral Connector

Legacy connector that powered older hard drives, case fans, and accessories. Still occasionally used for fan controllers and LED strips. Delivers up to 132W. Nearly obsolete in modern builds. A rectangular 4-pin connector with one rounded corner to prevent backward insertion.

9. Floppy Drive 4-Pin Berg Connector

Powered 3.5-inch floppy drives. Completely obsolete but occasionally needed for certain RAID controller battery backup units. A tiny 4-pin connector about half the size of Molex. If needed, buy a Molex-to-Berg adapter.

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PART 2: SERVER AND RACK-MOUNT POWER SYSTEMS

Server power supplies work fundamentally differently from desktop PSUs. Instead of internal cables, they use hot-swappable modules that plug into a power backplane.

10. Hot-Swap PSU Modules (Gold-Finger Common Slot)

Rack servers from Dell PowerEdge, HP ProLiant, and Lenovo ThinkSystem use standardized power supply modules that slide into a cage at the rear of the chassis. The PSU connects via a gold-plated edge connector that mates with a backplane inside the cage. The backplane distributes 12V DC to the motherboard, drives, and fans through internal traces. No individual cables to connect.

With redundant PSUs in N+1 configuration, you can remove and replace one PSU while the server continues running on the remaining unit.

Common wattages by use case:

• 495W to 550W: Entry-level single-CPU servers
• 750W to 800W: Dual-CPU servers with moderate drive counts
• 1100W to 1200W: Fully loaded dual-CPU servers with many drives
• 1400W to 1600W: GPU-equipped servers
• 2000W to 2400W: Multi-GPU AI and ML training servers

Always replace with the exact same wattage and part number. Mixing different wattage PSUs causes load-sharing imbalances and automatic shutdowns.

11. Server Internal Power Distribution

Inside the server, the PSU backplane feeds power through proprietary connectors:

Drive backplane connector: A proprietary plug feeds 12V and 5V to the drive backplane which distributes power to all hot-swap drive bays. You never touch these unless replacing the backplane.

GPU power headers: Some servers like Dell R740 GPU edition and HP DL380 Gen10 with GPU kit have internal 8-pin PCIe power cables running from the PSU backplane to GPU riser cards. These are server-model-specific and must be ordered as part of the GPU enablement kit.

Fan power: Server fans receive power through proprietary board-to-board connectors that are not user-serviceable.

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PART 3: DATA CENTER POWER DISTRIBUTION CABLES

External power cables that connect servers to PDUs and PDUs to facility power.

12. IEC C13/C14 Power Cables (10A Standard)

The most common data center power cable. C14 plug (male, goes into PDU outlet) to C13 connector (female, plugs into server or switch). Rated for 10A at 250V giving a maximum of 2500W.

Used for standard rack servers, network switches, and storage arrays. When ordering a Dell PowerEdge or HP ProLiant, the included power cord typically has a C13 on one end and a wall plug on the other. For PDU connections, replace with a C14-to-C13 cable. Available in 2ft, 4ft, 6ft, and 10ft lengths. Choose the shortest length that reaches to minimize cable clutter.

13. IEC C19/C20 Power Cables (16A/20A High Power)

C20 plug (male) to C19 connector (female). Rated for 16A at 250V (4000W) internationally and 20A in North America. Used for high-power servers including 4U chassis, blade enclosures like Dell M1000e and HP c7000, large UPS systems, and GPU-dense servers.

The C19/C20 connectors are noticeably larger than C13/C14. The C19 has flat horizontal pins in a row while C13 has rounded pins in a triangular pattern. If your server power inlet is the larger rectangular shape (C20 inlet), you need C19/C20 cables.

14. IEC C15/C16 High-Temperature Power Cables

Identical to C13/C14 but rated for 120 degrees Celsius instead of 70 degrees. The C15 connector has a small notch that prevents cross-mating with standard C14 inlets. Used for PoE switches, network equipment in hot environments, and high-power Cisco and Aruba switches that generate significant heat at the power inlet.

15. Locking Power Cables (V-Lock, SecureLock)

C13 or C19 cables with a mechanical locking clip that prevents accidental disconnection. The lock engages when fully seated and requires pressing a release tab to remove. Used for mission-critical servers in environments where compliance frameworks like SOC 2 and PCI DSS require physical cable security. Make sure your locking cable type matches the locking receptacle on your PDU.

16. PDU Input Whip Cables

The thick power cable permanently attached to the PDU that connects to the facility breaker panel. Common plug types include NEMA L5-30P for 30A 120V single-phase, NEMA L6-30P for 30A 208V (standard North American data center), NEMA L6-20P for 20A 208V smaller PDUs, and IEC 60309 for international data centers in 16A 32A and 63A versions. These come permanently attached to the PDU and are specified when ordering.

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PART 4: HOW TO CHOOSE THE RIGHT CABLES

Desktop and Workstation Builds

Buy a modular or semi-modular PSU and only connect cables you need. Never mix cables between different PSU brands or models because the pinout on the PSU end varies even when the device end looks identical. For GPU power, count required connectors and make sure your PSU provides enough native cables without relying on daisy-chain adapters for high-power GPUs.

Rack Servers

Always match PSU wattage and part number exactly when replacing. Order correct cable lengths for your rack layout. Use C19/C20 only if your server has a C20 inlet. For redundant power, run each PSU to a different PDU fed by a different circuit to protect against PDU failure and breaker trips.

Data Center Deployments

Label every cable at both ends with server hostname and PSU number. Use color-coded cables: one color for A-side PDU, another for B-side. Use locking cables for all production equipment. Stock spare C14-to-C13 and C20-to-C19 cables for emergency deployments.

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Cable Wattage Quick Reference

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Buy Power Supplies, Cables, and Connectors

Pro Disk Network stocks over 20,000 power supplies and thousands of power cables for Dell, HP, Lenovo, Cisco, and APC equipment. Whether you need a replacement 750W hot-swap PSU for a PowerEdge R740, a set of C14-to-C13 locking cables for your rack, or a complete PDU for a new cabinet, we have it in stock.

Search by part number or server model at prodisknetwork.com. Volume pricing is available for data center buildouts. Contact sales@prodisknetwork.com or use the live chat for help identifying the right cable. All orders over 150 dollars ship free within the US.