MSI PRO B840M-B AM5 mATX Motherboard - DDR5, PCIe 4.0
MSI
MSI PRO B840M-B AM5 mATX Motherboard - DDR5, PCIe 4.0
The MSI PRO B840M-B is a compact AM5 motherboard built for AMD Ryzen 9000, 8000 and 7000 series processors, with DDR5 support and PCIe 4.0 connectivity. It combines a solid power delivery system with practical features like dual M.2 slots, 2.5G LAN and front USB Type-C, making it suitable for builders who need performance without a full-size board.
Why this product
DDR5 with up to 12% latency reduction
This board supports DDR5 memory at 8000+ MT/s (overclocked) across two DIMM slots, paired with MSI's Memory Boost technology and dedicated SMT welding to maximise performance.
7+2+1 direct power design
Digital power phases with an 8-pin CPU connector and Load-Line Calibration keep voltage stable under load, improving headroom for demanding workloads and overclocking.
PCIe 4.0 and dual Gen 4 M.2 slots
One x16 PCIe 4.0 slot and two M.2 Gen4 x4 64Gbps slots deliver fast expansion for graphics and NVMe storage without compromise.
2.5G LAN for stable networking
Realtek 8125 controller provides reliable wired connectivity suitable for multimedia work and competitive gaming.
Compact mATX form factor
244 × 226 mm footprint fits smaller cases while retaining four SATA ports, dual M.2 slots and seven USB 5Gbps ports for connectivity.
- SocketAMD AM5
- Form factormATX
- Memory supportDDR5 up to 8000+ MT/s (OC), 128GB max
- Storage2 × M.2 Gen4 x4, 4 × SATA
- Expansion1 × PCIe 4.0 x16, 1 × PCIe 3.0 x1
- USB ports7 × USB 5Gbps + 6 × USB 2.0
- Networking2.5G LAN
- SKUMSI-7379
- EAN4711377360166
- Fits AMD Ryzen 9000, 8000 and 7000 series processors on Socket AM5.
- Works with mATX and smaller ATX cases; dimensions are 244 × 226 mm.
- Accepts standard DDR5 UDIMMs up to 8000+ MT/s (overclocked), 128GB maximum across two slots.
- Dual BIOS protects against corruption during flashing and accidental short-circuit damage.
- Display output requires processor graphics; no dedicated GPU VRAM needed, but built-in video only reaches 4K 60Hz over HDMI 2.1.
Best for
- Budget-conscious Ryzen 9000 builds
- Small-form-factor systems and compact cases
- DDR5 performance builds on a tighter budget than high-end boards
- Builders who value dual M.2 and four SATA for mixed storage
Trade-offs
- Full-size ATX cases: mATX design does not fill a standard ATX board area.
- Multiple graphics cards: single x16 PCIe 4.0 slot and one x1 PCIe 3.0 slot limit expansion.
- Extreme overclocking: while stable, this is a mainstream board not targeted at advanced enthusiasts.
- Wireless networking: no Wi-Fi module; 2.5G LAN only.
PRO B840M-B is engineered with many exclusive features of MSI, PCIe 4.0 M.2, EZ PCIe Clip II, 2.5G LAN, and Front Type-C, ready for the AMD Ryzen™ 9000 series processors.
DIRECT 7+2+1 POWER DESIGN
Unleash and sustain the maximum performance with a VRM design built with a total of 7+2+1 digital power phases. With an 8-pin power connector, PRO B840M-B is ready for the challenge of heavy-loading tasks.
OPTIMIZED PCB SOLUTION
The PCB design has been optimized for higher bandwidth and faster transfer speeds, which is also beneficial for reliable circuit transmission.
- 6 PCB layers
- 2oz Thickened Copper
MORE FOR PERFORMANCE
What you set, is what you get. LLC makes sure your CPU voltage remains 100% stable under any load. This greatly improves stability when demanding more CPU performance.
Dual BIOS — Prevents potential short-circuit damage to the CPU and other critical components.
DDR5 MEMORY SUPPORT WITH HIGH PERFORMANCE
A huge step of DDR performance enhancement with the latest DDR5 memory. Combines with dedicated SMT welding process and MSI Memory Boost technology, PRO B840M-B is ready to deliver the world-class memory performance.
Latency Killer
UP TO 12% Memory latency Reduction
Board
| Brand | MSI |
|---|---|
| Model | PRO B840M-B |
| Chipset | AMD B840 |
| Form factor | mATX |
| Dimensions | 244 × 226 mm |
| CPU support | AMD Ryzen 9000, 8000, 7000 series (Socket AM5) |
Memory & Storage
| Memory slots | 2 × DDR5 UDIMM |
|---|---|
| Memory speed | 8000+ MT/s (OC) |
| Maximum memory | 128GB |
| M.2 slots | 2 × Gen4 x4 64Gbps |
| SATA ports | 4 × 6Gbps |
Connectivity & Ports
| PCIe slots | 1 × PCIe 4.0 x16, 1 × PCIe 3.0 x1 |
|---|---|
| USB 5Gbps | 7 ports (6 Type-A + 1 Type-C) |
| USB 2.0 | 6 ports |
| LAN | Realtek 8125 2.5G |
| Audio | 8-channel (7.1) HD Audio with Audio Boost |
| Video output | HDMI 2.1 (4K 60Hz), VGA (requires processor graphics) |
Power & Features
| Power delivery | 7+2+1 digital power phases, 8-pin CPU connector |
|---|---|
| Voltage regulation | Load-Line Calibration (LLC) |
| PCB layers | 6 layers, 2oz thickened copper |
| BIOS | Dual BIOS |
| OS support | Windows 11 64-bit |
Shipping
All our products are shipped from the United Kingdom within 24 to 48 hours of purchase. See our Shipping and Returns page for full details.
Returns
- Tech Syndicate offers a full money-back guarantee on all purchases made in our store. If you are not satisfied with your purchase, we will provide a full refund, no questions asked.
- Refunds are available within 45 days of delivery.
- After the 45-day period you are no longer eligible for a refund, so we encourage you to try the product within the first few weeks to make sure it fits your needs.