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Black micro-ATX board with grey heatsinks and reinforced PCIe slot

MSI

MSI MAG B550M MORTAR AMD motherboard

SKU CH-XY85-PYZ0M

Micro ATX AMD B550 board with Socket AM4 for Ryzen CPUs, dual-channel DDR4 up to 128GB, 2.5Gbps LAN and 7.1 audio

  • CPU Socket TypeSocket AM4
  • CPU TypeSupports AM4 socket 3rd Gen AMD Ryzen processors, and future
  • ChipsetAMD B550
  • Memory StandardSupport dual-channel DDR4 1866/2133/2400/2667/2800/2933/3000
  • Maximum Memory Supported128GB
  • PCI Slots1x PCIe 3.0/ 4.0 x16 slot (PCI_E1) 1x PCIe 3.0 x16 slot (PCI
  • Supports up to 128GB DDR4 for heavy multitasking
  • 5Gbps Realtek LAN for fast wired networking
  • 1-channel Realtek audio for immersive sound
  • PCIe 3.0 and 4.0 x16 slots for flexible GPU options
  • AM4 socket ready for 3rd Gen Ryzen and future CPUs with BIOS update

Socket AM4 foundation

The MSI MAG B550M MORTAR is a Micro ATX board built around the AMD B550 chipset for Socket AM4 processors. It targets builders who want a compact platform for 3rd Gen Ryzen CPUs and newer Ryzen chips after a BIOS update. The layout fits smaller cases while keeping the core connectivity of a full-size design.

128 GB DDR4 ceiling

Four slots accept dual-channel DDR4 from 1866 up to 4400 MHz, topping out at 128 GB total. That headroom covers heavy multitasking and content workloads; beyond 128 GB the board simply cannot address more memory. Two M.2 sockets and six SATA III ports give plenty of drive lanes before you run out of connectors.

2.5 Gbps Realtek LAN

The single network controller is a Realtek RTL8125B running at 2.5 Gbps. If your switch or router only negotiates 1 Gbps you will not see the extra throughput, and there is no second LAN port for failover or aggregation.

Highlights

  • Supports up to 128GB DDR4 for heavy multitasking
  • 5Gbps Realtek LAN for fast wired networking
  • 1-channel Realtek audio for immersive sound
  • PCIe 3.0 and 4.0 x16 slots for flexible GPU options
  • AM4 socket ready for 3rd Gen Ryzen and future CPUs with BIOS update

Specifications

BrandMSI
SeriesMSI MAG B550M MORTAR
ModelMSI MAG B550M MORTAR
CPU Socket TypeSocket AM4
CPU TypeSupports AM4 socket 3rd Gen AMD Ryzen processors, and future AMD Ryzen processors with BIOS update
ChipsetAMD B550
Memory StandardSupport dual-channel DDR4 1866/2133/2400/2667/2800/2933/3000/3066/3200/3466/3600/3733/3866/4000/4133/4266/4400 + MHz memory
Maximum Memory Supported128GB
PCI Slots1x PCIe 3.0/ 4.0 x16 slot (PCI_E1)
1x PCIe 3.0 x16 slot (PCI_E4), supports x4 mode
2x PCIe 3.0 x1 slots
SATA RAID2XM.2 interface, 6xSATA III interface
Audio ChipsetRealtek ALC1200/ALC1220P Codec
7.1-Channel High Definition Audio
Supports S/PDIF output
LAN Chipset1x Realtek RTL8125B 2.5Gbps LAN controller
Onboard USBAMD B550 Chipset
3x USB 3.2 Gen 1 5Gbps ports (1 Type-C internal connector, and 2 ports are available through the internal USB 3.2 Gen 1 5Gbps connector)
6x USB 2.0 ports (2 Type-A ports on the back panel, 4 ports through the internal USB 2.0 connectors)
AMD Processor
2x USB 3.2 Gen 2 10Gbps ports (1 Type-C port and 1 Type-A port on the back panel)
2x USB 3.2 Gen 1 5Gbps Type-A ports on the back panel

Questions about this item

Will a Ryzen 3000 series CPU work on this board without a BIOS update?

The board supports AM4 socket 3rd Gen Ryzen processors and future Ryzen processors with a BIOS update.

How can I confirm the 2.5Gbps LAN is active after build?

Check Device Manager for the Realtek RTL8125B adapter and verify link speed shows 2.5 Gbps in the network status window.

Which accessories ship with the motherboard and what must I supply?

The box includes the motherboard, a CMOS battery, one SATA cable and the rear I/O shield; you must provide CPU, DDR4 memory, storage, power supply and case.

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