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Micro ATX motherboard dark PCB silver heatsinks rear I/O shield

ASUS

ASUS Prime B550M-A WiFi II AMD motherboard AM4 3rd Gen Ryzen Micro ATX

SKU CH-2NKG-Q96FS

Micro-ATX AM4 board with PCIe 4.0, WiFi 6, dual M.2 slots, 128 GB DDR4 support and 7.1 audio

  • ProcessorSupports AMD Ryzen 5000 Series / 5000 G-Series / 4000 G-Seri
  • ChipsetAMD B550
  • Form factorMicro ATX
  • CPU socketAM4
  • Memory slot count4 × 288pin (DDR4)
  • Supported memoryDDR4 4866(OC) / 4800(OC) / 4600(OC) / 4466(OC) / 4400(OC) /
  • Ready for 3rd Gen Ryzen CPUs with AM4 socket and PCIe 4.0
  • Fast networking via WiFi 6 and 1Gb LAN plus USB 3.2 Gen 2 Type-A
  • Dual M.2 slots with one at PCIe 4.0 x4 for NVMe drives
  • 128GB DDR4 over four slots with OptiMem layout for higher speeds
  • 8+1 DrMOS power stages with alloy chokes for stable multi-core loads

Socket AM4 Micro-ATX Board

This Micro-ATX motherboard uses the AMD B550 chipset and Socket AM4 for Ryzen 5000 Series, 5000 G-Series, 4000 G-Series and 3000 Series processors. It targets builders who want a compact platform with PCIe 4.0 support and integrated WiFi 6 connectivity. Four DDR4 slots accept up to 128 GB of memory in dual-channel mode.

VRM Heatsink And SafeSlot

An 8+1 DrMOS power stage design with alloy chokes and durable capacitors feeds the CPU, while a VRM heatsink and PCH heatsink dissipate heat. The primary PCIe 4.0 x16 slot uses a reinforced SafeSlot core. Rear I/O includes HDMI 2.1 for 4K 60 Hz output, D-Sub, DVI, USB 3.2 Gen 2 Type-A, 1 Gb LAN and stainless-steel construction. Addressable Gen 2 RGB and standard RGB headers enable Aura Sync lighting control.

PCIe 4.0 M.2 And Memory Limits

The primary M.2 slot runs at PCIe 4.0 x4 with Ryzen 5000 and 3000 Series CPUs, but drops to PCIe 3.0 x4 with 5000 G-Series and 4000 G-Series chips. The second M.2 slot and two PCIe 3.0 x1 slots share bandwidth with the chipset. DDR4 speeds above 3200 MT/s require overclocking and depend on the specific processor and memory kit installed.

How it compares

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

Price $128.99
Cheaper than about 67% of the 1,906 comparable items (median $224.49).

New to this? Buying PC parts with Monero — what to check, what it costs to pay, and what is never asked for.

Specifications

Product
Brand nameASUS
Model namePRIME B550M-A WIFI II
Part number90MB19 × 0-M0AAY0
Processor
ProcessorSupports AMD Ryzen 5000 Series / 5000 G-Series / 4000 G-Series / 3000 Series Processors
* Refer to www.asus.com for CPU support list.
CPU socketAM4
ChipsetAMD B550
Memory
Memory slot count4 × 288pin (DDR4)
Supported memoryDDR4 4866(OC) / 4800(OC) / 4600(OC) / 4466(OC) / 4400(OC) / 4333(OC) / 4266(OC) / 4200(OC) / 4133(OC) / 4000(OC) / 3866(OC) / 3733(OC) / 3600(OC) / 3466(OC) / 3400(OC) / 3333(OC) / 3200 / 3000 / 2933 / 2800 / 2666 / 2400 / 2133*
* Refer to www.asus.com for the Memory QVL (Qualified Vendors Lists), and memory frequency support depends on the CPU types.
Max supported RAM128 GB
Memory channelsDual Channel
ECC supportECC memory (ECC mode) support varies by CPU
BufferingUn-buffered
Storage
SATA ports4 x SATA 6Gb/s
M.2 slotsAMD Ryzen 5000 Series/ 3000 Series Desktop Processors:
M.2_1 slot (Key M), type 2242/2260/2280/22110 (supports PCIe 4.0 x4 & SATA modes)
AMD Ryzen 5000 G-Series/ 4000 G-Series Desktop Processors:
M.2_1 slot (Key M), type 2242/2260/2280/22110 (supports PCIe 3.0 x4 & SATA modes)
AMD B550 Chipset:
M.2_2 slot (Key M), type 2242/2260/2280 (supports PCIe 3.0 x4 & SATA modes)
SATA and RAID support0/1/10
Graphics
Onboard video chipSupported only by CPU with integrated graphic
Audio & video
Audio chipRealtek 7.1 Surround Sound High Definition Audio CODEC
Sound channels7.1 Channels*
* A chassis with an HD audio module in the front panel is required to support 7.1 Surround Sound audio output.
Connectivity
Ethernet controllerRealtek 1Gb Ethernet
Maximum network speed1 Gbit/s
Wi-Fi standardWi-Fi 6
802.11 a/b/g/n/ac/ax
Bluetooth support5.2
Ports & slots
PCIe 4.0 x16 slots1 x PCI Express 4.0 x16*
* Actual support may vary by CPU.
PCIe x1 slots2 x PCIe 3.0 x1
Onboard USB headers1 x USB 3.2 Gen 1 header supports additional 2 USB 3.2 Gen 1 ports
2 x USB 2.0 headers support additional 4 USB 2.0 ports
Power
Power connectors1 × 24-pin Main Power connector
1 × 8-pin +12 V Power connector
Size & build
Form factorMicro ATX
Width and length9.6 in × 9.6 in
Compatibility
Windows 11 supportReady
More details
LightingRGB

Questions about this item

Does the PCIe 4.0 x16 slot run at full 4.0 speed with a Ryzen 5000 series CPU?

The single PCIe 4.0 x16 SafeSlot operates at PCIe 4.0 x16 when a Ryzen 5000 or 3000 series desktop processor is installed; actual support may vary by CPU.

What case clearance does the Micro ATX board and its VRM heatsink require?

The board uses the Micro ATX form factor with a VRM heatsink and PCH heatsink; it fits any case that accepts Micro ATX motherboards and provides standard CPU cooler clearance around the socket area.

How do I enable WiFi 6 and Bluetooth on this motherboard, and which step is often missed?

Install the supplied external antennas on the rear I/O WiFi 6 (802.11ax) connectors, then install the driver from the ASUS support page; the step often missed is attaching both antennas before first boot.

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