A technician is troubleshooting a newly built PC that powers on but fails to boot or display video. During physical inspection, the technician observes that an 8-pin power cable labeled 'EPS12V' is plugged directly into the auxiliary 8-pin power header of the PCI Express (PCIe) graphics card. Which of the following best explains why this cabling configuration prevents the system from functioning properly?
- EPS12V connectors have a different pinout layout than 8-pin PCIe power connectors, resulting in mismatched pin voltage assignments.Answer
- BEPS12V cables supply only +3.3 V and +5 V power rails, failing to deliver the required +12 V line to the expansion card.
- CEPS12V cables are designed exclusively for motherboard M.2 storage drives and cannot exceed a power delivery threshold of .
- DEPS12V connectors trigger an automatic motherboard firmware lock that suppresses POST diagnostic beep codes.
Answer
EPS12V connectors have a different pinout layout than 8-pin PCIe power connectors, resulting in mismatched pin voltage assignments.
EPS12V 8-pin motherboard power connectors and 8-pin PCIe power connectors use different pinout wiring standards. EPS12V delivers ground on pins 1–4 and +12 V on pins 5–8, whereas 8-pin PCIe connectors supply +12 V on pins 1–3 and ground/sense on pins 4–8. Inserting an EPS12V cable into a PCIe graphics card header creates a short-circuit condition that prevents system startup.
Step-by-Step Solution
Key Concept
Power supply unit connector pinout specifications and PCIe auxiliary expansion card power standards