How to Choose a Motherboard: Chipsets, VRMs, M.2 Lanes and Ports

Buy the cheapest board that has the ports, M.2 slots and power delivery your build needs. Above that point, extra money mostly buys features you will never touch and heatsinks you will only see in photos. Start with your CPU's socket, pick a chipset, then read the spec page's fine print on lane sharing, which is where most nasty surprises live.

Chipsets

The chipset sets the ceiling for overclocking and connectivity. On AM5, AMD's own table lays out the differences.

For most builds, buy B850 on AM5 or B860 on LGA1851. AMD's table specifies PCIe 4.0 graphics on B850, although most B850 boards in our motherboard category run the main slot at PCIe 5.0. It hardly matters yet, since Tom's Hardware notes no current graphics card gains from PCIe 5.0 bandwidth.

Move up to X870 for USB4 as standard, or Z890 if you want to overclock an Intel K chip. All AM5 boards work with all AM5 processors, though 600-series boards may need a BIOS update for newer chips. Intel's Core Ultra 200S Plus chips run on existing 800-series boards. Our AM5 vs LGA1851 comparison and the opinion piece on overspending on motherboards go further.

VRMs

The voltage regulator modules turn 12 V from the power supply into the voltage your CPU uses, and they need to handle the chip's maximum draw without overheating. Marketing leans on phase counts, but a better measure is the total current the power stages can handle, along with the size of the heatsinks.

For a sense of scale, Tom's Hardware counted 12 Vcore phases with 60 A stages on the MSI MAG B860 Tomahawk WiFi, a modest setup by its reckoning that still ran a flagship-class chip without trouble. The ASRock X870E Taichi carries 24 stages rated at 110 A, far more than most people will ever use.

Use this rule. For chips up to about 170 W, such as a Ryzen 7 9800X3D or a Core Ultra 5 250K Plus, any decent B850 or B860 board with real VRM heatsinks is fine. For chips reaching 230 W to 270 W, such as the Ryzen 9 9950X, Core Ultra 7 270K Plus or Ryzen 9 9950X3D2, choose a mid-tier board or better and look for VRM temperatures in a review. Be careful with entry-level boards, and check the maker's CPU support list before pairing them with a high-power chip. Remember that liquid coolers remove the airflow an air cooler would blow across the VRM.

M.2 slots and PCIe lane sharing

A CPU has a limited pool of PCIe lanes. A Ryzen 7 9800X3D offers 24 usable lanes, and a Core Ultra 200S chip tops out at 24 too. Motherboards divide those between the graphics slot and M.2 drives, and some slots only work by borrowing from something else.

Real examples from our catalog:

• On the ASUS TUF Gaming X870-Plus WiFi, the main x16 slot drops to x8 when M.2_2 is used.
• On the ASUS ROG Maximus Z890 Hero, the main slot runs at x8 when M.2_3 or M.2_4 is populated.
• On the MSI MAG X870 Tomahawk WiFi, M2_2 and the rear 40 Gbps USB-C ports share PCIe 5.0 lanes, and both run at x2 when M2_2 is populated by default.
• On the MSI MAG B650 Tomahawk WiFi, M2_3 and the second PCIe slot run at x2 when both are in use.

An x8 link on PCIe 5.0 still offers the bandwidth of PCIe 4.0 x16, so a modern card loses little. It can matter more on older generations or with a card that has run short of VRAM. Install your first SSD in the slot that shares nothing, and read the manual's bandwidth table before you buy. Also check slot lengths: many boards accept 2280 drives only on some slots. Our PCIe lanes explainer covers the concepts.

Rear I/O and USB

Count what you will plug in, then add two. Rear USB-A ports range from 4 on the MSI PRO H810M-E to 12 on the Gigabyte Z890 Aorus Master. A keyboard, mouse dongle, headset, microphone and webcam can fill a small panel quickly, as our desk setup guide shows.

Check these as well:

• USB4 or Thunderbolt: standard on X870 and X870E, optional on B850, and absent on the B850 boards in our catalog. Needed for fast external storage and laptop-style docks.
• Front USB-C header: required if your case has a USB-C front port.
• Video outputs: these only work with a CPU that has integrated graphics. The rear DisplayPort on the ASUS ProArt X870E Creator WiFi is input only.
• Ethernet: 2.5 GbE is common, 5 GbE appears on boards like the MSI MAG B850 Tomahawk Max WiFi, and 10 GbE on workstation models.

Wi-Fi

Wi-Fi 7 is now common on new boards. Most of its headline speed comes from 320 MHz channels in the 6 GHz band, so you need a matching router and a module that supports them. Not all do: Tom's Hardware lists 160 MHz Wi-Fi 7 as a drawback on one budget X870 board. Gigabyte also changes Wi-Fi modules between board revisions on some models, so check the revision.

If your PC is wired, skip Wi-Fi and save money. The Gigabyte B850M DS3H has none, and a PCIe adapter can add it later. Our Wi-Fi 7 explainer has the details.

Form factors

Mini-ITX boards also typically limit you to 128 GB of memory across two slots. Back-connect boards, such as the ASUS ROG Maximus Z890 Hero BTF, need a compatible case and graphics card.

BIOS Flashback

BIOS Flashback updates firmware from a USB drive without a CPU or memory installed. ASUS calls it USB BIOS FlashBack, MSI uses a Flash BIOS Button and Gigabyte has Q-Flash Plus. It matters when your CPU is newer than the board's factory BIOS, such as a Ryzen 9000 chip on an older B650 board.

Most boards in our catalog have it, but cheaper models may not. The MSI PRO B860M-A WiFi and PRO H810M-E both skip it. If your board lacks it and the BIOS is too old for your CPU, you will not be able to boot and update without borrowing an older, supported chip. Our BIOS update guide covers the process.

The PC builder checks socket and memory compatibility for you, and our rankings list current recommendations.