ASUS PRIME B850M-A WIFI-CSM AMD AM5 DDR5 mATX Motherboard
The ASUS PRIME B850M-A WIFI-CSM is a micro-ATX AMD B850 motherboard for Ryzen 9000, 8000 and 7000 series processors on socket AM5. It suits business, home office and creator PC builds that need up to 256GB of DDR5, a PCIe 5.0 graphics slot, three M.2 slots, Wi-Fi 6E and 2.5Gb Ethernet.
Key features
- PCIe 5.0 ready: a PCIe 5.0 x16 graphics slot and a PCIe 5.0 x4 M.2 slot with Ryzen 9000 and 7000 processors.
- Up to 256GB DDR5: 4 DIMM slots, up to 8000+ MT/s (OC), with AMD EXPO and ASUS AEMP support.
- Three M.2 slots plus 4 SATA: room for multiple NVMe SSDs, with an M.2 heatsink to help keep drives cool.
- Wi-Fi 6E, Bluetooth 5.3 and 2.5Gb LAN: fast wired and wireless networking without an add-in card.
- Easy to build and update: pre-mounted I/O shield, BIOS FlashBack button, Q-Antenna and Q-DIMM design.
Specifications
| Model | PRIME B850M-A WIFI-CSM |
| CPU socket | AMD AM5 |
| Supported CPUs | AMD Ryzen 9000, 8000 and 7000 series desktop processors (up to 170W) |
| Chipset | AMD B850 |
| Memory | 4 x DIMM, max. 256GB DDR5, dual channel; ECC and non-ECC unbuffered; up to 8000+ MT/s (OC) |
| Expansion slots | 1 x PCIe 5.0 x16 (Ryzen 9000/7000; PCIe 4.0 x8/x4 with Ryzen 8000); 1 x PCIe 4.0 x16 (x1 mode, chipset) |
| M.2 | M.2_1 2280 PCIe 5.0 x4; M.2_2 2280 PCIe 4.0 x4; M.2_3 2242/2260/2280 PCIe 4.0 x4 (speeds vary with Ryzen 8000) |
| SATA | 4 x SATA 6Gb/s; RAID support varies by CPU |
| Graphics outputs | 2 x DisplayPort (up to 8K@30Hz), 1 x HDMI (up to 4K@60Hz); depends on CPU |
| Ethernet | 1 x Realtek 2.5Gb with ASUS LANGuard |
| Wireless | Wi-Fi 6E 2x2 (2.4/5/6GHz); Bluetooth 5.3 |
| Rear USB | 2 x USB 10Gbps Type-A, 2 x USB 5Gbps Type-A, 4 x USB 2.0 Type-A |
| Front USB | 1 x USB 5Gbps Type-C connector, 1 x USB 5Gbps header (2 ports), 2 x USB 2.0 headers (4 ports) |
| Audio | Realtek 7.1 surround HD audio codec, up to 24-bit/192kHz; 3 rear audio jacks |
| Power connectors | 24-pin main, 8-pin +12V, 4-pin +12V |
| Fan headers | 1 x CPU, 1 x CPU OPT, 1 x AIO pump, 3 x chassis (all 4-pin) |
| Internal headers | COM, S/PDIF out, SPI TPM, chassis intrusion, 3 x Addressable RGB Gen 2 |
| BIOS | 256Mb flash ROM, UEFI AMI BIOS, BIOS FlashBack button |
| Form factor | Micro ATX, 24.4 x 24.4 cm |
| Operating system | Windows 11, Windows 10 (64-bit) |
| In the box | 2 x SATA cables, Wi-Fi Q-Antenna, M.2 rubber package, 2 x M.2 screw packages, quick start guide |
Compatibility
ASUS lists support for AMD Ryzen 9000, 8000 and 7000 series desktop processors on socket AM5, up to 170W. PCIe 5.0 graphics and M.2 speeds need a Ryzen 9000 or 7000 series CPU; Ryzen 8000 series processors run these slots at PCIe 4.0. Memory must be DDR5. Check ASUS's CPU support list for the BIOS version your processor needs.
Who it's for
Suited to: AMD-based office, business, home and content-creation PCs in a micro-ATX case, especially builds that want fast NVMe storage and built-in Wi-Fi 6E.
Not suited to: Intel processors or DDR4 memory. For an Intel build, see the ASUS PRIME B760M-A WIFI-CSM; for a full-size ATX AMD board, the ASUS PRIME B850-PLUS WIFI-CSM. Browse all ASUS motherboards and components.
FAQs
Does the ASUS PRIME B850M-A WIFI-CSM support Ryzen 9000 processors?
Yes. ASUS lists support for AMD Ryzen 9000, 8000 and 7000 series desktop processors on socket AM5.
How much memory does it support?
Up to 256GB of DDR5 across 4 DIMM slots, with ECC and non-ECC unbuffered modules supported.
How many M.2 SSDs can I install?
Three. M.2_1 supports PCIe 5.0 x4 with Ryzen 9000/7000 CPUs, and the other two run at PCIe 4.0 x4, plus there are 4 SATA ports.
Does it have built-in Wi-Fi?
Yes. It has Wi-Fi 6E (2x2) and Bluetooth 5.3, with the ASUS Wi-Fi Q-Antenna included.
