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Rectangular ATX motherboard in matte black with silver heatsinks and a rear I/O shield

MSI

MSI MEG B550 UNIFY AM4 AMD motherboard

SKU CH-KF89-NJC32

ATX board with AM4 socket, four DDR4 slots up to 128 GB, one PCIe 4.0 x16 slot, six SATA ports and four M.2 slots

  • ProcessorSupports AMD Ryzen 5000 & 3000 Series desktop processors (no
  • ChipsetAMD B550
  • Form factorATX
  • CPU socketAM4
  • Memory slot count4 × 288pin (DDR4)
  • Supported memoryAMD Ryzen 4000 G-Series processors support DDR4 5100+ (Max.
  • Supports Ryzen 5000 and 3000 series processors via AM4 socket
  • Four DDR4 slots deliver up to 128 GB dual-channel memory capacity
  • PCIe 4.0 x16 slot enables full-bandwidth graphics and storage
  • Four M.2 slots accept 2280 and 22110 devices with SATA and PCIe 3.0 or 4.0 support
  • Realtek ALC1220P codec provides 7.1-channel audio with S/PDIF output

AM4 B550 motherboard for Ryzen 5000 and 3000 series

This ATX motherboard uses the AMD B550 chipset and AM4 socket. It supports Ryzen 5000 and 3000 series desktop processors, plus Ryzen 4000 G-Series CPUs. The board does not work with Ryzen 5 3400G or Ryzen 3 3200G.

Four DDR4 slots and four M.2 slots suit

Builders needing up to 128 GB of dual-channel DDR4 and multiple M.2 drives will fit here. The second PCIe x16 slot runs at x4 speed and disables when an M.2 SSD occupies M2_4. Both x1 slots disable when M2_2 is used in chipset mode. Users wanting full x16 bandwidth on a second GPU should look elsewhere.

Dual-channel DDR4 up to 128 GB

Ryzen 4000 G-Series CPUs enable DDR4 speeds up to 5600 MHz via A-XMP OC MODE. The board handles 128 GB across four 288-pin slots comfortably. Memory support drops to standard JEDEC speeds with Ryzen 5000 or 3000 series chips, so maximum frequency depends on the installed processor.

How it compares

Measured against everything we stock in Motherboards for AMD CPUs, at today’s prices. Recalculated every night.

Price $121.99
Cheaper than about 69% of the 1,906 comparable items (median $224.49).

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Specifications

Product
Brand nameMSI
Model nameMEG B550 UNIFY
Processor
ProcessorSupports AMD Ryzen 5000 & 3000 Series desktop processors (not compatible with AMD Ryzen 5 3400G & Ryzen 3 3200G) and AMD Ryzen 4000 G-Series desktop processors
CPU socketAM4
ChipsetAMD B550
Memory
Memory slot count4 × 288pin (DDR4)
Max supported RAM128 GB
Memory channelsDual Channel
Storage
M.2 slots4 x M.2 slots (Key M)
M2_1 slot (from CPU):
Supports PCIe 4.0/3.0 x4*
Supports SATA 6Gb/s
Supports 2280/22110 storage devices
M2_2 slot:
Chipset support mode (default, from Chipset ) - supports PCIe 3.0 x2
CPU support mode (From CPU) - supports PCIe 4.0/3.0 x4 *
Supports 2280 storage devices
M2_3 slot:
Chipset support mode (default, from Chipset ) - supports PCIe 3.0 x2
CPU support mode (From CPU) - supports PCIe 4.0/3.0 x4 *
Supports SATA 6Gb/s
Supports 2280/22110 storage devices
M2_4 slot:
Supports PCIe 3.0 x4
Supports 2280 storage devices
* M.2 specifications may vary depending on
SATA and RAID support0/1/10
Audio & video
Audio chipRealtek ALC1220P Codec
Sound channels7.1-Channel High Definition Audio
Supports S/PDIF output
Connectivity
Ethernet controllerRealtek RTL8125B
Maximum network speed2.5 Gbit/s
Wi-Fi standardIntel Wi-Fi 6 AX200
The Wireless module is pre-installed in the M.2 (Key-E) slot
Supports MU-MIMO TX/RX, 2.4 GHz/5 GHz (160 MHz) up to 2.4 Gbit/s
Supports 802.11 a/ b/ g/ n/ ac/ ax
Bluetooth supportSupports Bluetooth 5.1
Ports & slots
PCIe 4.0 x16 slots1 x PCIe 4.0/3.0 x16 slot (PCI_E1) *
* The supported specification depends on installed processor.
PCIe 3.0 x16 slots1 x PCIe 3.0 x16 slot (PCI_E4), supports x4 speed
* The PCI_E4 slot will be unavailable, when installing M.2 SSD into M2_4.
PCIe x16 slots1 x PCI Express x16
USB 3.0 ports4 x USB 3.0
Onboard USB headers1 x USB 3.2 Gen 2 10 Gbit/s Type-C port
1 x USB 3.2 Gen 1 5 Gbit/s connector (supports additional 2 USB 3.2 Gen 1 5 Gbit/s ports)
2 x USB 2.0 connectors (supports additional 4 USB 2.0 ports)
Power
Power connectors1 × 24-pin ATX main power connector
2 × 8-pin ATX 12 V power connector
1 × 6-pin PCIE power connector
Size & build
Form factorATX
Width and length12.0 in × 9.6 in
Compatibility
Windows 11 supportSupported
More details
LightingRGB

Questions about this item

Does the MEG B550 UNIFY need a specific CPU cooler bracket for the AM4 socket?

The board uses the standard AM4 mounting holes, so any cooler labelled for AM4 fits without an extra bracket.

If I keep my PCIe 3.0 graphics card, will it run at full speed in the top slot?

The primary PCI_E1 slot supports PCIe 4.0 and 3.0 x16, so a PCIe 3.0 card operates at its native x16 speed.

How can I confirm the M.2 drive in the M2_1 slot is running at PCIe 4.0 x4?

Install a Ryzen 5000 or 3000 series CPU, then check the BIOS or OS device manager — it should report a PCIe 4.0 x4 link for M2_1.

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