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Green micro-ATX motherboard with black AM4 socket, four DDR4 slots, silver PCIe x16 slot, four SATA ports, M.2 slot, rear I/O shield

MSI

MSI B550M-A PRO AMD B550 AM4 DDR4 64GB Micro ATX Motherboard

SKU CH-85FZ-E1BT4

Micro-ATX board for Socket AM4 Ryzen CPUs with dual-channel DDR4 up to 64 GB, PCIe 4.0 x16, four SATA III ports, 7.1 audio and gigabit LAN

  • ProcessorSupport 3rd Gen AMD Ryzen Desktop Processors and AMD Ryzen40
  • ChipsetAMD B550
  • CPU socketSocket AM4
  • Supported memorySupport dual-channel DDR4 1866/2133/2400/2667/2800/2933/3000
  • Max supported RAM64 GB
  • PCI slots1x PCIe 3.0 x1 slot 1x PCIe 4.0/3.0 x16 slot
  • Supports 3rd Gen Ryzen and Ryzen 4000 G-Series CPUs via Socket AM4
  • Dual-channel DDR4 up to 4600 MHz with 64 GB maximum capacity
  • PCIe 4.0 x16 slot plus PCIe 3.0 x1 slot for expansion cards
  • Realtek ALC892/897 codec delivers 7.1-channel high-definition audio
  • Realtek RTL8111H Gigabit LAN plus USB 3.2 Gen 1 and USB 2.0 connectivity

AM4 socket motherboard for Ryzen CPUs

The MSI B550M-A PRO is a micro-ATX board built around the AMD B550 chipset. It accepts Socket AM4 processors including 3rd Gen Ryzen desktop chips and Ryzen 4000 G-Series APUs. Dual-channel DDR4 memory runs at speeds from 1866 up to 4600+ MHz with a 64 GB capacity ceiling.

Builders needing one full-size GPU slot

This board suits compact systems that rely on a single PCIe 4.0 x16 graphics card and up to four SATA III drives plus one M.2 device. It lacks a second x16 slot and provides only one PCIe 3.0 x1 lane, so multi-GPU arrays or heavy add-in card counts are not practical.

Single PCIe 4.0 x16 slot for graphics

The only full-length expansion lane is a PCIe 4.0/3.0 x16 slot wired for a graphics card. No second x16 or x8 electrical lane exists, so the build cannot accommodate dual discrete GPUs or a GPU plus a high-bandwidth capture card.

How it compares

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

Price $74.99
Cheaper than about 84% of the 1,906 comparable items (median $224.49).

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Specifications

Product
Brand nameMSI
Product lineMSI B550M-A PRO
Model nameMSI B550M-A PRO
Processor
ProcessorSupport 3rd Gen AMD Ryzen Desktop Processors and AMD Ryzen4000 G-Series Desktop Processors
CPU socketSocket AM4
ChipsetAMD B550
Memory
Supported memorySupport dual-channel DDR4 1866/2133/2400/2667/2800/2933/3000/3066/3200/3466/3600/3733/3866/4000/4133/4266/4533/4600 + MHz memory
Max supported RAM64 GB
Storage
SATA and RAID support1XM.2 interface, 4xSATA III interface
Audio & video
Audio chipRealtek ALC892/ALC897 Codec
7.1-Channel High Definition Audio
Connectivity
Ethernet controller1x Realtek RTL8111H Gigabit LAN controller
Ports & slots
PCI slots1x PCIe 3.0 x1 slot
1x PCIe 4.0/3.0 x16 slot

Questions about this item

Will the CMOS battery need replacing on the MSI B550M-A PRO?

The board ships with a CMOS battery included; it typically lasts several years before a replacement is required.

What limits sustained performance on the MSI B550M-A PRO?

The VRM heatsink area is the first constraint during long heavy loads on Socket AM4 Ryzen CPUs.

How loud and hot does the MSI B550M-A PRO get under all-day use?

Passive VRM cooling and the Realtek RTL8111H LAN run silently; chassis fans determine actual noise and temperature.

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