What is the extra 8-pin connector on X870 and Z890 motherboards for?

Some of the latest X870 and Z890 motherboards from the likes of MSI and ASUS have an extra 8-pin power connector at the bottom of the PCB. But what’s it for? What problem is it solving? Answer: To provide more power for your expansion cards—your graphics card in particular. Is this something PC builders need though? That’s a bit tougher to answer, but let’s go over some of the details first.

The graphics cards pf today are power hungry beasts. Or at least they can be. By way of example, the RTX 4090 can draw up 450W. Even the RTX 4080 16GB is rated at 320W. And this is something we can only imagine will go up with future generations of graphics cards. 600W isn’t completely out of the question for next-generation cards. These are peak power draws, but still, you don’t want to hold your expensive graphics card back because of lack of power.

With those power requirements in mind, it’s worth highlighting that the humble PCIe slot is rated to deliver just 75W—shy of what the graphics card wants. This is why graphics cards come bedecked with all manner of additional power connectors, ranging from single and double PCIe 8-pin connectors on older cards to the latest 12V-2x6 connectors that can be found on Nvidia’s RTX 40 Series offerings. Those PCIe 8-pin connectors can deliver up to 300W, while the 12V-2x6 doubles that to 600W.

Having additional power cables stretching to your graphics card can make things untidy though, so the idea of having that power delivered directly via the PCIe slot itself is attractive. More power for the components that need them, without having ugly cables everywhere is something plenty of system builder can get behind. MSI explains that the 8-pin Supplemental PCIe Power Connector on the MSI MAG X870 TOMAHAWK WIFI provides up to 420W of power to ensure that top-end hardware operates at their full potential, where it may struggle otherwise.

A win for everyone? Possibly, but there are issues.

While providing additional power to the motherboard could be useful for USB charging ports or for overclocking, the idea that this will solve the graphics card power problem is a bit of a stretch. Graphics cards are already demanding more than such a solution can deliver. They may help the situation, but they can’t be their own reason for existing.

Essentially, the 8-pin connector adds 150W to what the PCIe slot is already rated for, equating to 225W all in. That’s not enough for the top-end graphics cards, or even the ones a few steps down from that. Such connectors have appeared on motherboards before, where they were used more for overclocking than trying to power graphics cards without additional connectors. It’s worth noting that your graphics card would need to support drawing this much power from the socket too, which is potentially limiting.

The takeaway from all of this is that there’s a good chance you’ll see motherboards going forward with additional power connectors. There’s nothing to suggest that these are needed for normal use though, including for high-end gaming systems. Additional power connectors can be of interest to overclockers, where stability under ultra-high loads is going to be more important, but for everyone else it’s something that can help with stability but isn’t something you need. A good quality power supply though? That makes a lot more sense.