Resource Cheatsheet
A+ Core 1 3.5: Motherboard Connections
A+ Core 1 3.5 — main and PCIe power connectors, SATA/eSATA, front-panel/USB/TPM headers, and M.2.
- Updated
- Reading time
- 4 min read
- Detail
- A+ Core 1
- Detail
- Motherboard Connections
On this page
In one line: the connectors on a board — keyed main power (20/24-pin), PCIe card power (6-pin 75 W / 8-pin 150 W), L-shaped SATA data, case pin headers, and cable-free M.2.
Companion to: Professor Messer A+ Core 1 (220-1201), Section 3, objective 3.5. The full version is the Motherboard Connections class notes; the section overview is the Section 3 sheet.
Power connectors
| Connector | Pins | Delivers | Notes |
|---|---|---|---|
| Main board power | 20-pin (old) / 24-pin (new) | +3.3 V, +5 V, +12 V DC | Keyed, latched; 24-pin cable fits a 20-pin board (4 left off) |
| PCIe card power | 6-pin | 75 W (+12 V) | Extra power for cards, usually GPUs |
| PCIe card power | 8-pin | 150 W (+12 V) | Often a 6+2 cable (2 pins detach) |
| CPU power (EPS)* | 8-pin | +12 V | Different keying — not the PCIe 8-pin |
*Covered in the power lesson, not this one — but do not confuse the two 8-pin connectors.
Data connectors
| Connector | Carries | Shape / notes |
|---|---|---|
| SATA (internal) | Data only | L-shaped; power is a separate SATA lead; one cable = one drive |
| eSATA | Data (external) | External SATA; back-panel port or eSATA expansion card |
| M.2 | Data and power | Small slot; push drive in, fasten screw, no cables |
Header pins (wire the case to the board)
| Header | Connects |
|---|---|
| Front panel | Power button, reset button, power LED, HDD-activity LED |
| USB header | Case front USB ports — USB 2.0 and USB 3.0 |
| TPM header | Trusted Platform Module (v1 / v2) |
| Speaker | Internal beep speaker |
- Always follow the labels printed on the board — front-panel pinouts differ per board.
- LEDs are polarised (reverse the connector if it won’t light); switches are not.
🔐 Security notes
- Internal USB headers are USB ports policy forgets: an implant on an internal header or rogue front-panel cable sits on the bus, hidden behind the case panel, past external-port controls. Count internal USB in your USB threat model; an opened case is the event.
- A discrete TPM sits on a removable header with a comparatively exposed bus — the basis of TPM-sniff/swap attacks against Secure Boot and disk encryption. Physical case access is what it needs, so the chassis lock is part of the crypto threat model.
- eSATA is raw external disk access outside the case, easy to miss in a USB-only device-control policy.
Practice drills
1. Which three voltages does the main power connector supply?
+3.3 V, +5 V and +12 V DC.
2. Can a 24-pin cable power a 20-pin board?
Yes — plug it in and leave the extra four pins off (often a detachable 4-pin block on modular PSUs).
3. Wattage of a PCIe 6-pin vs 8-pin connector?
6-pin = 75 W, 8-pin = 150 W, both +12 V DC.
4. What is a 6+2 PCIe cable?
An 8-pin plug whose two extra pins detach, so one cable serves a 6-pin or 8-pin card.
5. What does the L-shaped SATA connector carry, and where's the power?
Data only — power comes on a separate SATA power lead.
6. Wiring the front panel, what do you rely on, and what if an LED won't light?
Follow the labels printed on the board; reverse the LED connector (LEDs are polarised, switches aren’t).
7. How do you install an M.2 drive?
Push it into the M.2 slot and fasten the retaining screw — the slot carries both data and power.
Key takeaways
- Main power: keyed, latched, +3.3/+5/+12 V; 20-pin or 24-pin (24 fits 20 with 4 off).
- PCIe card power: 6-pin = 75 W, 8-pin = 150 W; often a 6+2 cable. Don’t confuse the 8-pin PCIe with the 8-pin CPU (EPS).
- SATA = L-shaped, data only; eSATA is external; M.2 needs no cables.
- Headers wire the case (power/reset/LEDs, USB 2.0/3.0, TPM, speaker) — follow the board’s labels.
- Security: internal USB and TPM headers are inside-the-case attack surfaces the external-port policy misses.