This article covers MSI MAG B850M MORTAR WIFI Micro-ATXマザーボード MB6758.

Overview

MSI's MAG B850M MORTAR WIFI is a Micro-ATX motherboard built around the AMD B850 chipset, supporting Socket AM5 CPUs from the Ryzen 9000, 8000, and 7000 series. Its 12+2+1 phase Duet Rail Power System with 60A Smart Power Stages (SPS) ensures stable power delivery even for high-core-count Ryzen 9 processors, making it a solid foundation for a compact yet powerful build. On the connectivity front, it comes with both 5G LAN and Wi-Fi 7 out of the box, offering future-proof wired and wireless networking. Storage expansion is equally generous: two PCIe 5.0 x4 M.2 slots plus one PCIe 4.0 x2 M.2 slot, alongside four SATA 6Gb/s ports. Large heatsinks with 7W/mK thermal pads keep the VRM and M.2 drives cool under load. This board targets enthusiasts who want high-end features in a space-saving Micro-ATX form factor without sacrificing performance or upgrade potential.

Compatibility Guide

The motherboard is exclusively compatible with AMD Socket AM5 processors (Ryzen 9000/8000/7000). It has four DDR5 UDIMM slots supporting up to 256GB with speeds beyond 8200MHz via overclocking, and AMD EXPO profiles are supported. Form factor is Micro-ATX (244×244mm), so any case supporting Micro-ATX or larger (ATX) will work. Expansion includes one PCIe 5.0 x16 slot and one PCIe 4.0 x4 slot. The M.2 slots are two PCIe 5.0 x4 (from CPU and chipset) and one PCIe 4.0 x2 (from chipset). SATA: 4 ports. Power connectors: a 24-pin ATX main and an 8-pin CPU power. For a high-end Ryzen 9 build with a powerful GPU, a 700W or higher PSU is recommended.

Product Info

Available since mid-2025, the MSI MAG B850M MORTAR WIFI retails for around ¥35,000 in Japan (tax included). It comes with a 3-year warranty through authorized Japanese distributors. Positioned in the mid-to-high-end segment, this board packs features normally found on more expensive X870 models: dual PCIe 5.0 M.2 slots, 5G LAN, Wi-Fi 7, and a robust VRM. It's an excellent choice for those building a compact high-performance system without paying a premium for the flagship chipset.

Best Use Cases

Compact high-end gaming rig: Perfect for Micro-ATX cases housing a Ryzen 7 or 9 CPU and a powerful GPU. The strong VRM and efficient cooling ensure stable performance during long gaming sessions. Content creation with fast storage: With two Gen5 M.2 slots, creators can run RAID 0 for video projects or simply install multiple high-speed SSDs for asset libraries and scratch disks. * Future-proof workstation: AM5 platform with DDR5 and PCIe 5.0 means you can upgrade to faster CPUs, GPUs, and SSDs down the line without changing the motherboard. ## Alternatives
Main competitors in the same B850 Micro-ATX segment include the ASUS TUF GAMING B850M-PLUS WIFI and the GIGABYTE B850M AORUS ELITE WIFI6E. The MSI stands out with dual PCIe 5.0 M.2 slots (ASUS offers only one), and Wi-Fi 7 (GIGABYTE sticks with Wi-Fi 6E). If 5G LAN and the extra M.2 slot matter to you, the MSI card is the stronger pick. For users who don't need the extra connectivity, a B650 board could save money while still offering solid performance.

Things to Consider

The Micro-ATX form factor limits expansion to just two PCIe slots. If you plan to use multiple add-in cards (e.g., capture card, sound card, 10G NIC), you'll run out of space quickly. The PCIe 4.0 x4 slot is in a fixed position that may block GPU airflow depending on case layout. Wi-Fi 7 is still early-adopter territory; you'll need a compatible router to take full advantage. The board's 2.5GbE would be more than sufficient for most current networks. Both PCIe 5.0 M.2 slots generate significant heat when using high-performance Gen5 SSDs. While the bundled heatsinks help, you may want to add active cooling or use slower Gen4 drives if thermals are a concern. Lastly, if you don't need dual Gen5 M.2 or 5G LAN, consider stepping down to a B650 board to save money without sacrificing core performance.

Product Disclosure (Amazon)

  • Manufacturer: MSI
  • Seller: Amazon.co.jp
  • Fulfilled by: Amazon.co.jp
  • ASIN: B0F4Q45RKX
  • Note: This article covers a manufacturer-made product based on Amazon listing details.