ASUS Prime B550M-K AM4 Micro-ATX Motherboard: features, specs and fit

The ASUS Prime B550M-K is a Micro-ATX motherboard with an AMD AM4 socket. It is a foundation for a mainstream or DIY PC built around Ryzen 5000 series or 3rd Gen Ryzen processors. This page explains what the main specs mean and what to confirm before building around it.

Socket and processor support

AM4 is the processor socket, and the board is built for Zen 3 Ryzen 5000 and 3rd Gen Ryzen CPUs. ASUS gives one clear warning: if you install a Ryzen 5000 series processor, make sure the BIOS is up to date. Boards sometimes ship with older firmware that doesn't recognise newer processors, so check the support page for your exact CPU, and see the ASUS site's BIOS and firmware downloads for this model.

What PCIe 4.0 means here

PCIe is the interface that links the processor to graphics cards and fast storage. PCIe 4.0 offers about twice the bandwidth per lane of PCIe 3.0. The board has one PCIe 4.0 x16 SafeSlot for a graphics card. PCIe 4.0 also depends on the processor: the listing refers to 3rd Gen Ryzen and Ryzen 5000 CPUs, and PCIe generations can differ by processor model, so check your CPU's specification.

Storage: dual M.2 slots

There are two M.2 slots for NVMe SSDs, one with PCIe 4.0 x4 connectivity. NVMe drives are much smaller and typically much faster than 2.5-inch SATA drives. A PCIe 4.0 x4 slot lets a PCIe 4.0 SSD run at its full rated speed, whereas a PCIe 3.0 drive works too at its own speed. Check the manual for how the M.2 slots share bandwidth with other storage ports.

Ports and display output

• LAN: 1Gb Ethernet, with LANGuard protection for the network port.
• USB: USB 3.2 Gen 2 Type-A, which is rated at up to 10 Gbps.
• Video: HDMI 2.1 supporting 4K at 60Hz, DisplayPort 1.2, plus DVI and D-Sub.

The video outputs only work with a processor that has integrated graphics. Many Ryzen 5000 chips don't, in which case you need a separate graphics card. Check your CPU's specification.

Memory

The listing mentions ECC memory support. ECC (error-correcting code) memory can detect and fix certain memory errors, but it requires compatible ECC modules and a processor that supports it. For most home builds, standard non-ECC modules are the usual choice. Check ASUS's memory support list for the supported speeds, capacities and number of slots.

Cooling and protection

ASUS lists a PCH heatsink, hybrid fan headers and the Fan Xpert 2 utility for managing fan speeds. The "5X Protection III" feature set includes LANGuard, DRAM overcurrent protection, overvoltage protection, SafeSlot Core and a stainless-steel back I/O panel.

Size and who it suits

At about 10.6 x 10.4 inches and 1.1 lb, it is a Micro-ATX board, smaller than full ATX, so it fits Micro-ATX and ATX cases but not mini-ITX-only cases. It suits compact and mainstream desktop builds, home and office computers, and anyone upgrading within the AM4 platform.

What to check before you buy

• CPU compatibility: check the exact processor against ASUS's support list, and BIOS version.
• Graphics: whether your CPU has integrated graphics for the video outputs.
• Memory: type, capacity and speed supported.
• Case: confirm the case takes Micro-ATX boards.
• Expansion: count the slots, SATA ports and headers you need. A Micro-ATX board has fewer than full ATX.
• Wireless: the listing doesn't mention Wi-Fi, so you may need an adapter.
• Offers: the Adobe offer in the listing has expired, so don't rely on it.

The short version

• Micro-ATX AM4 motherboard for Ryzen 5000 and 3rd Gen Ryzen processors.
• PCIe 4.0 x16 slot and dual M.2 slots, one at PCIe 4.0 x4.
• 1Gb LAN, USB 3.2 Gen 2 Type-A, HDMI 2.1 (4K at 60Hz), DisplayPort 1.2, DVI and D-Sub.
• PCH heatsink, hybrid fan headers and Fan Xpert 2.
• Update the BIOS before using a Ryzen 5000 CPU.

Bloiq is reader-supported. Some links may earn us a commission; it never affects what we write. How we make money.