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Green micro-ATX board with silver heatsinks and black I/O shield

ASUS

ASUS 90MB1LN0-MVAAYC PRIME B850M-A WIFI-CSM AMD motherboard

SKU CH-QXJ9-ABDG0 MPN 90MB1LN0-MVAAYC

An AM5 mATX board for Ryzen 7000, 8000 and 9000 CPUs with DDR5 up to 8000 MT/s, PCIe 5.0 x16 and M.2 slots, Wi‑Fi 6E and 2.5 Gb LAN

  • ProcessorRyzen 7000 Series / Ryzen 8000 Series / Ryzen 9000 Series
  • ChipsetAMD B850
  • Form factorMicro ATX
  • CPU socketAM5
  • Memory slot count4 × 288pin (DDR5)
  • Supported memorySupports up to 8000+MT/s (OC)
  • Ready for AI workloads with AM5 socket support for Ryzen 9000, 8000 and 7000 series processors
  • Stable business supply through ASUS CSM programme with end-of-life notifications and IT management software
  • Simplified enterprise administration via ASUS Control Center Express remote monitoring and management
  • Reliable power delivery using 6-layer PCB, alloy chokes and durable capacitors for consistent performance
  • Ultrafast connectivity with Wi-Fi 6E, PCIe 5.0 x16 slot, PCIe 5.0 M.2 slot, Realtek 2.5Gb Ethernet and USB 10Gbps Type-A ports

AM5 socket for Ryzen 7000 8000 9000 series

This mATX board targets builders who need a stable platform for AMD Ryzen 7000 8000 and 9000 series processors. The CSM programme guarantees long-term availability and IT management tools for business deployments. Dual-channel DDR5 memory supports up to 256 GB with AMD EXPO and ASUS AEMP profiles. PCIe 5.0 x16 and a PCIe 5.0 M.2 slot come from the CPU on Ryzen 9000 and 7000 models.

VRM M.2 PCH heatsinks Fan Xpert 2+

A six-layer PCB with alloy chokes and durable capacitors feeds the CPU while VRM M.2 and PCH heatsinks dissipate heat. Hybrid fan headers and Fan Xpert 2+ adjust airflow to workload so the system stays quiet under normal desktop use. Realtek 2.5 Gb Ethernet Wi-Fi 6E and rear USB 10 Gbps Type-A ports keep network and peripheral traffic moving without extra cards.

PCIe 5.0 M.2 slot from CPU

The M.2_1 slot runs at PCIe 5.0 x4 when paired with Ryzen 9000 or 7000 series processors and drops to PCIe 4.0 x4 with Ryzen 8000 series. A second M.2_2 slot provides PCIe 4.0 x4 storage. Four SATA 6 Gbps ports add bulk capacity. This CPU-dependent lane split is the single spec that decides whether the board fits a given build.

How it compares

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

Price $141.99
Cheaper than about 64% of the 1,906 comparable items (median $224.49).

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Specifications

Product
Brand nameASUS
Model namePRIME B850M-A WIFI-CSM
Processor
ProcessorRyzen 7000 Series / Ryzen 8000 Series / Ryzen 9000 Series
CPU socketAM5
ChipsetAMD B850
Memory
Memory slot count4 × 288pin (DDR5)
Supported memorySupports up to 8000+MT/s (OC)
Max supported RAM256 GB
Memory channelsDual Channel
Memory profilesAMD EXPO
ECC supportYes
BufferingUn-buffered
Storage
SATA ports4 x SATA 6Gb/s
M.2 slotsAMD Ryzen 9000 & 7000 Series Desktop Processors
M.2_1 slot (Key M), type 2280 (supports PCIe 5.0 x4 mode)
M.2_2 slot (Key M), type 2280 (supports PCIe 4.0 x4 mode)
AMD Ryzen 8000 Series Desktop Processors
M.2_1 slot (Key M), type 2280 (supports PCIe 4.0 x4 mode)
M.2_2 slot (Key M), type 2280 (supports PCIe 4.0 x4/x2 mode)*
AMD B850 Chipset
M.2_3 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4 mode)
SATA and RAID supportAMD RAIDXpert2 Technology
Ryzen 9000 Series Processors: RAID 0/1/5/10
Ryzen 8000 Series Processors: RAID 0/1
Ryzen 7000 Series Processors: RAID 0/1/10
Audio & video
Sound channelsRealtek 7.1 Surround Sound High Definition Audio CODEC*
- Supports: Jack-detection, Multi-streaming, Front Panel Jack-retasking
- Supports up to 24-Bit/192 kHz playback
Audio Features
- Audio Shielding
- Premium audio capacitors
- Dedicated audio PCB layers
* A chassis with an HD audio module in the front panel is required to support 7.1 Surround Sound audio output.
Connectivity
Maximum network speed2.5 Gbit/s
Wi-Fi standardWi-Fi 802.11 ax
Bluetooth support5.4
Ports & slots
PCIe 5.0 x16 slotsAMD Ryzen 9000 & 7000 Series Desktop Processors
1 x PCIe 5.0 x16 slot (supports x16 mode)
AMD Ryzen 8000 Series Desktop Processors
1 x PCIe 4.0 x16 slot (supports x8/x4 mode)
PCIe 4.0 x16 slotsAMD B850 Chipset
1 x PCIe 4.0 x16 slot (supports x1 mode)
Onboard USB headers1 x USB 5 Gbit/s connector (supports USB Type-C)
1 x USB 5 Gbit/s header supports 2 additional USB 5 Gbit/s ports
2 x USB 2.0 headers support 4 additional USB 2.0 ports
Power
Power connectors1 × 24-pin Main Power connector
1 × 8-pin +12 V CPU Power connector
1 × 4-pin +12 V CPU Power connector
Size & build
Form factorMicro ATX
Width and length9.6 in × 9.6 in
Shipping weight1.36 kg
Package size279 × 279 × 76 mm
Compatibility
Windows 11 supportSupported
In the box
In the boxCables
2 x SATA 6Gb/s cables
Miscellaneous
1 x ASUS WiFi Q-Antenna
1 x M.2 rubber package
1 x Screw package for M.2 SSD
Documentation
1 x Quick start guide
More details
BIOS256 Mb Flash ROM, UEFI AMI BIOS

Questions about this item

How do I install the AM5 processor and what step is most often missed?

Lift the socket lever, align the triangle on the CPU with the socket corner, lower the lever and lock it; the step often missed is removing the protective cover from the socket before placing the processor.

What maintenance will the board need over its life?

Dust the VRM and M.2 heatsinks periodically and clean the fan headers so Fan Xpert 2+ can keep temperatures stable.

What limit appears first during sustained heavy loads?

The VRM and M.2 heatsinks set the thermal ceiling; once they saturate, Fan Xpert 2+ ramps the hybrid headers to maximum airflow.

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