Your board has a 24-pin socket and one or two sockets for CPU power. The board maker and the PSU maker do not answer this the same way, so here is what each of them actually says
Two sources, both first-party, and they do not stress the same thing. ASUS's manual for the ROG Strix B850-E Gaming WiFi says "Ensure to connect the 8-pin power plug, or connect both the 8-pin power plugs." Corsair, which makes the power supplies, says "In general though, unless you are doing extreme overclocking, you don't typically need to connect both CPU power cables." Neither says the second connector is mandatory; ASUS presents both as acceptable and Corsair says one is enough short of extreme overclocking. The 24-pin is not optional in either account. Check your own board's manual before you decide — the caution text differs from board to board, and on at least one ASUS board it is stricter than this.
There are two kinds of power socket on a motherboard and they do different jobs. ASUS describes the group in one line in its manuals: "These Power connectors allow you to connect your motherboard to a power supply."
The 24-pin. The wide one, usually along the right-hand edge. It is the board's own supply — chipset, slots, most of what is soldered down. ASUS's specification sheets list it as "1 x 24-pin Main Power connector", and every board in this article has exactly one.
The 8-pin (and sometimes a second one). Up at the top of the board, near the CPU socket. This is the CPU's +12V supply, listed on ASUS's sheets as a "8-pin +12V CPU Power connector". Corsair gives the industry names for the two sizes: "These connectors are usually referred to as EPS12V for an eight-pin connector and ATX12V for a four-pin connector." Boards ship with one 8-pin, two 8-pins, or an 8-pin plus a 4-pin.
The names printed on the board. This is where it gets confusing, because ASUS does not use one set of labels across its own range. Two boards we review, both from ASUS, print different things:
ATX_PWR for the 24-pin and CPU_12V_1 and CPU_12V_2 for the two 8-pins.EATXPWR for the 24-pin, and EATX12V_1 and EATX12V_2 for CPU power.So ATX_PWR and EATXPWR are the same thing, and CPU_12V_n and EATX12V_n are the same thing. Other vendors print their own variants. The label is not a specification — treat it as a name to look up in your board's manual, not as something to decode.
One more trap in that numbering. On the B550-F Gaming WiFi II the two CPU sockets are not the same size, and the number does not tell you which is which: the manual's pinout diagram shows EATX12V_1 with eight contacts (four marked +12V DC, four GND) and EATX12V_2 with four (two +DC_IN, two GND). Count the contacts in the diagram; do not assume _1 and _2 are a matched pair.
ASUS states this for the power connectors specifically, in both manuals: "The power supply plugs are designed to fit in only one orientation. Find the proper orientation and push down firmly until the power supply plugs are fully inserted." Getting one round the wrong way is not the failure mode here. A plug that is almost seated is, and so is an empty socket.
This is the question, and the honest answer is that the board maker and the PSU maker emphasise different things. We are going to quote both rather than average them into a rule neither one states.
What ASUS instructs. The user manual for the ROG Strix B850-E Gaming WiFi — a current AM5 board with two 8-pin sockets — carries this as a boxed caution in the power connectors section: "CAUTION! Ensure to connect the 8-pin power plug, or connect both the 8-pin power plugs." Read that carefully: it is an or. ASUS is not telling you to fill both. It is telling you that one 8-pin is a valid configuration and two is a valid configuration, and by omission that anything less is not.
The same manual immediately follows it with a note about capacity rather than connector count: "We recommend that you use a PSU with a higher power output when configuring a system with more power-consuming devices. The system may become unstable or may not boot up if the power is inadequate." That is about the supply, not the cabling.
What Corsair says. Corsair, writing as a power supply manufacturer, is more direct: "In general though, unless you are doing extreme overclocking, you don't typically need to connect both CPU power cables." It describes the ordinary case explicitly: "That said, a common scenario is a motherboard with two eight-pin EPS connectors, and a power supply with only one cable, so connect the one closest to the CPU and leave the other one empty, as shown below."
Corsair also draws the line for when the second one earns its keep: "If you want to do extreme overclocking with liquid nitrogen and advanced cooling you will need the power from that second connector." Liquid nitrogen is the example it chooses, not a stock build with a good air cooler.
Its reasoning is a capacity argument. Corsair puts a single eight-pin EPS cable at over 300W, a four-pin ATX12V connector at around 190W, and concludes from those figures that no consumer CPU sold today needs more than 300W for standard use. Those are Corsair's numbers and Corsair's conclusion; we have not measured anything and we are not adding a threshold of our own.
They do not contradict each other on what is permitted — ASUS's "the 8-pin, or both" and Corsair's "one is typically enough" both allow a single populated 8-pin. They diverge in emphasis: ASUS words it as an instruction with two acceptable outcomes and stops there, while Corsair recommends one of them for most builders. Your board's manual outranks both. The caution text is written per board, it is not the same on every board even within ASUS, and the next section is a board where it is stricter.
Some boards do not have two 8-pin sockets. They have one 8-pin and one 4-pin beside it — an "8+4" layout. The ASUS ROG Strix B550-F Gaming WiFi II is one: its specifications list "1 x 8-pin +12V Power connector" and "1 x 4-pin +12V Power connector".
The manual's caution for that board is a two-line box, and the second line is the one people miss:
Two things fall out of that. First, the 8-pin is the one that must be populated, and the 4-pin is the optional extra — not the other way round, and not either-or. Second, ASUS names a consequence here that it does not name for the two-8-pin board: overheating under heavy usage if you feed the CPU through the 4-pin alone. This is the one place on this page where a manufacturer states an outcome for getting it wrong, and it is worth taking at face value.
Corsair reaches the same practical answer for this layout from the other direction: "As long as the main 8-pin connector is populated, you can safely leave the 4-pin next to it empty." Both sources agree on 8+4: fill the 8, the 4 is optional.
Boards with an 8+4 layout also get a separate PSU recommendation in the ASUS manual, and it is a floor rather than a target: "For a fully configured system, we recommend that you use a power supply unit (PSU) that complies with ATX 12V Specification 2.0 (or later version) and provides a minimum power of 350W."
A board with two CPU sockets and a power supply with one CPU cable is an extremely common pairing, and it is not a mismatch. Corsair's advice for it is quoted in full above: connect the one closest to the CPU and leave the other empty.
The wrinkle is what that single cable looks like. Corsair describes the usual construction: "the EPS12V cables that come with a power supply are usually a 4+4 design, so they can be broken off into two four-pin connectors exactly for this purpose" — the purpose being to fit boards that have only a 4-pin socket. For an 8-pin socket the two halves go back together: "If you only have one cable and it's a 4+4 and there is an eight-pin slot, you connect both cables to each other and then plug them into the slot."
That is the detail that trips people up, because a 4+4 cable pulled apart looks like two cables. It is not. It is one cable with a split end, and the two halves belong in the same socket unless your board's only CPU socket is a 4-pin.
Neither of our two sources states whether splitting a single 4+4 cable across two separate CPU sockets is acceptable, and we found no first-party statement either way. This page therefore makes no claim about it. Corsair's own instruction for a one-cable build is to fill one socket and leave the other empty, so that is what we quote and that is as far as the sourcing goes. If you want two sockets populated, the question to ask about your PSU is how many CPU cables it ships with, not how many ends one cable has.
The other half of "what your PSU ships" is capacity rather than connectors, and both manufacturers are on the same page there. ASUS's note for the B850-E is quoted above; it also adds a case for the far end of the range: "If you want to use two or more high-end PCI Express x16 cards, we recommend using a PSU with 900W~1200W power or above to ensure the system stability."
Nothing but fans. A board with the 24-pin seated and no CPU power at all is the single most common first-build miss, and it does not look like a power problem — the fans spin, so the machine appears to be running. Our guide to a system that will not POST covers the wider diagnosis; the check that matters here is the top-of-board connector, not the wide one.
The board that will not flash. If you are using a no-CPU BIOS flash button, the board is otherwise empty and it is easy to assume the CPU lead is not needed. It is: our BIOS update guide repeats MSI's instruction to connect both the CPU power connector and the 24-pin for that procedure, and ASUS's own ATX power connection step for the B550-F Gaming WiFi II says the same thing in four words — "Ensure to connect the 8-pin power plug."
Instability under load. ASUS attributes this to inadequate supply rather than to an empty second socket: "The system may become unstable or may not boot up if the power is inadequate." On an 8+4 board fed through the 4-pin alone, it also names overheating under heavy usage, quoted in full above. We have no test bench and have not reproduced either, so treat those as the manufacturer's statements rather than as our findings.
The ten-second check. Power off at the wall, look at the top edge of the board near the CPU socket, and confirm every socket that is meant to be filled has a plug pushed fully home. Then look at the wide connector on the right-hand edge and do the same. A plug that is one click short of seated looks identical to one that is in.
How many CPU power sockets a board has is on its specification page, in the Internal I/O Connectors row under the Power Related heading. Our own spec tables do not carry that row, so it is a per-board lookup — but the answer is not a mystery, and it varies by tier rather than by socket or vendor generation. Seven boards we review, straight from ASUS's own published specifications:
Note the pattern and note its limits. Two 8-pins turn up on a current AM5 mid-ranger and on a previous-generation Intel ATX board alike; the two boards here with one are a Mini-ITX board and an entry-level Micro-ATX board, both of them AM5. Form factor and tier track this better than socket or generation do. Corsair's own summary of the market says "Most midrange to high-end motherboards today have two 8-pin connectors for CPU power." That is a general statement about the market and not a prediction about any specific board — the seven above are the ones we checked, and for anything else, read the Power Related lines on that board's own specification page.
The reviews index has the boards we cover, and each review links out to the manufacturer's page where those lines live.
ATX_PWR / CPU_12V_1 / CPU_12V_2 labels, the orientation instruction, the "8-pin power plug, or ... both" caution and the two PSU capacity notes. The specifications summary supplies the 24-pin and 2 x 8-pin counts.EATXPWR / EATX12V_1 / EATX12V_2 labels and their contact counts, the "DO NOT connect the 4-pin power plug only" caution, the 8+4 instruction and the 350W ATX 12V 2.0 recommendation; and section 2.1.6, ATX power connection, for "Ensure to connect the 8-pin power plug."Every quotation on this page was read from the source linked beside it on 9 September 2026: the two ASUS user manuals, the Corsair explainer, and six ASUS specification pages. We have no test bench. No connector on this page was populated, unpopulated or measured by us, no board was run with a socket left empty to see what happened, and nothing here is a benchmark. Where the two manufacturers emphasise different things we have quoted both rather than picking one, and where neither states an answer — splitting one 4+4 cable across two sockets, and any wattage threshold of our own — this page says so instead of filling the gap. Board manuals differ; yours is the one that governs your board.
Published 9 September 2026. Manufacturer sources read on 9 September 2026.