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Zorluk: ZorMotherboards Form Factors and Connectors

A technician is assembling a workstation motherboard that features two 8-pin auxiliary CPU power connectors required for multi-rail power stability. The power supply unit provides one dedicated 8-pin EPS12V connector and several 8-pin (6+2) PCIe power connectors. Which of the following describes the outcome if the technician attempts to plug an 8-pin PCIe power cable into the secondary 8-pin CPU power socket on the motherboard?

  1. The cable will fail to insert cleanly due to mismatched plastic pin keying, and forcing it will cause a short circuit because EPS12V and 8-pin PCIe cables have reversed +12V and Ground pinout configurations.Cevap
  2. B
    The system will power on normally because 8-pin PCIe and 8-pin EPS12V connectors utilize identical pinout layouts and voltage tolerances.
  3. C
    The motherboard will boot into UEFI/BIOS, but CPU performance will be throttled because 8-pin PCIe cables supply +5V direct current instead of +12V.
  4. D
    The power supply will automatically trip its overvoltage protection and shut down because PCIe cables carry double the amperage of EPS12V cables.

Cevap

The cable will fail to insert cleanly due to mismatched plastic pin keying, and forcing it will cause a short circuit because EPS12V and 8-pin PCIe cables have reversed +12V and Ground pinout configurations.
The EPS12V motherboard CPU power connector and the 8-pin PCIe expansion power connector have different physical keying shapes (square vs. beveled pin housings) and opposing pinouts. On EPS12V, the +12V lines are positioned along the clip side, whereas on PCIe 8-pin, the Ground lines are on the clip side. Forcing a PCIe cable into an EPS12V socket shorts the 12V rail directly to Ground.

Adım Adım Çözüm

1
Identify the primary purpose and pinout structure of the EPS12V motherboard power connector.
The 8-pin EPS12V connector provides +12V power dedicated to the CPU, with +12V wires located on the side closest to the retaining clip/latch and Ground wires on the opposite side.
Motherboards require clean, dedicated EPS12V lines for processor voltage regulation modules (VRMs).
2
Compare the EPS12V specification to the 8-pin (6+2) PCIe auxiliary power connector specification.
The 8-pin PCIe power cable has Ground wires on the side with the clip/latch and +12V lines on the bottom row, which is the exact inverse of EPS12V.
PCIe connectors are designed to supply power to add-in graphics cards rather than motherboard CPU sockets.
3
Evaluate the mechanical keying and consequences of cross-connecting these power cables.
The plastic housings have different square and chamfered (rounded) pin patterns to prevent accidental insertion. Forcing the connection connects +12V directly to Ground, causing an immediate electrical short circuit.
Physical keying prevents fatal power polarity reversals on motherboard headers.

Anahtar Kavram

Motherboard EPS12V vs PCIe 8-Pin Power Connectors
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Motherboards Form Factors and Connectors

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