Asus Prime B840-Plus WiFi AMD AM5

Description

Reliable AM5 Foundations with ASUS Prime Polish

The Prime B840-Plus WiFi is ASUS’s entry-level 800-series ATX offering, bringing the B840 chipset to a full ATX form factor with the build-quality touches ASUS Prime is known for: DIGI+ VRM, LANGuard surge protection, SafeSlot reinforced PCIe slot, audio shielding with dedicated PCB layers, and a pre-mounted I/O shield for cleaner installation. The 8+2+1 phase power design with discrete MOSFETs is honest entry-level fare — stable and efficient for mainstream Ryzen 7000/9000 builds, with support for CPUs up to 170W TDP. An 8-pin plus optional 4-pin ATX12V connector configuration provides flexibility for a range of builds without over-speccing power delivery for the chipset tier.

⚠️ The B840 chipset does not support CPU overclocking. Memory overclocking via AMD EXPO and ASUS AEMP profiles is supported. If CPU OC is a requirement, step up to B850 or X870.

⚠️ The 8+2+1 discrete MOSFET power stage is best suited to 65–105W TDP processors. It will run 170W-rated CPUs at stock, but sustained heavy all-core workloads on top-end Ryzen 9 chips are outside the optimal operating range of this VRM. For high-TDP builds, consider the B850 tier.

Memory and Storage

Four DDR5 DIMM slots support dual-channel operation up to 256 GB, with AMD EXPO and ASUS AEMP profile support for memory overclocking up to DDR5-7600+ (OC). Three M.2 slots cover the mainstream storage range: M2_1 and M2_2 are CPU-connected and run at PCIe 4.0 x4 (64 Gb/s) with Ryzen 7000/9000 processors, while M2_3 is chipset-connected at PCIe 3.0 x4 (32 Gb/s) and supports shorter 2242 and 2260 form factors in addition to 2280. Four SATA 6Gb/s ports are available for additional drives. RAID support varies by CPU generation: Ryzen 9000 supports RAID 0/1/5/10, Ryzen 7000 supports RAID 0/1/10, and Ryzen 8000 supports RAID 0/1 only.

⚠️ M2_2 drops from PCIe 4.0 x4 to x2 with Ryzen 8000 Phoenix 2 processors. Ryzen 9000 and 7000 CPUs run both M2_1 and M2_2 at the full PCIe 4.0 x4 rate.

⚠️ No M.2 slots on this board reach PCIe Gen5 speeds — M2_1 and M2_2 top out at Gen4 x4 (64 Gb/s). If PCIe Gen5 M.2 storage is a priority, look to B850 or X870 boards.

Connectivity and I/O

Rear I/O is well-rounded for the chipset tier: USB 10 Gbps Type-C and Type-A ports sit alongside two USB 5 Gbps Type-A and four USB 2.0 Type-A ports, plus HDMI 2.1 (4K 60Hz) and DisplayPort 1.4 (up to 8K 30Hz) for iGPU-equipped processors. Wi-Fi 6E (802.11ax, 2.4/5/6 GHz, 2×2 MU-MIMO) and Bluetooth 5.3 are onboard, alongside Realtek 2.5G LANGuard-protected Ethernet. A BIOS FlashBack button allows firmware updates without a CPU or RAM installed. Front panel connectivity includes a USB 5 Gbps Type-C header and a standard USB 5 Gbps header for two additional ports. Fan headers are generous: one CPU fan, one CPU OPT, one AIO pump, and four chassis fan headers. RGB support is provided via three Addressable Gen 2 (ARGB) headers with Aura Sync and Aura Creator compatibility. Bonus internal headers include a Thunderbolt/USB4 header, S/PDIF out, COM port, and SPI TPM.

⚠️ The primary PCIe 4.0 x16 GPU slot runs at full x16 with Ryzen 7000 and 9000 processors but drops to x8 or x4 with Ryzen 8000 Series CPUs. The chipset-side PCIe 3.0 slots also share bandwidth — the x4 slot (PCIEX16(G3)_2) drops to x1 mode when any of the adjacent chipset x16(G3)_1/3 or x1(G3) slots are occupied.

⚠️ Integrated display output (HDMI/DisplayPort) requires a Ryzen processor with integrated Radeon graphics. Non-G Ryzen 7000/9000 CPUs do not include an iGPU — a discrete GPU is required in those builds.

Key Highlights

• AMD B840 chipset, Socket AM5
• Supports Ryzen 7000, 8000, and 9000 Series, up to 170W TDP
• ATX form factor — 305 mm × 244 mm
• 8+2+1 phase power design, discrete MOSFETs, DIGI+ VRM
• 1× 8-pin + 1× 4-pin ATX12V CPU power connectors
• 4× DDR5 DIMM slots, dual-channel, up to 256 GB, DDR5 7600+ (OC)
• AMD EXPO and ASUS AEMP memory profile support
• 2× M.2 PCIe 4.0 x4 (CPU, 64 Gb/s) — M2_1 and M2_2
• 1× M.2 PCIe 3.0 x4 (chipset, 32 Gb/s, 2242/2260/2280) — M2_3
• 4× SATA 6Gb/s ports
• RAID 0/1/5/10 (Ryzen 9000) / 0/1/10 (Ryzen 7000) / 0/1 (Ryzen 8000)
• 1× PCIe 4.0 x16 (primary GPU) + 1× PCIe 3.0 x4 + 2× PCIe 3.0 x1 (chipset)
• HDMI 2.1 (4K 60Hz) + DisplayPort 1.4 (up to 8K 30Hz)
• Realtek 2.5G Ethernet with ASUS LANGuard
• Wi-Fi 6E (802.11ax, 2.4/5/6 GHz, 2×2 MU-MIMO) + Bluetooth 5.3
• Rear USB 10 Gbps Type-C + Type-A, 2× USB 5 Gbps Type-A, 4× USB 2.0 Type-A
• Front USB 5 Gbps Type-C header + 5 Gbps header (2 ports)
• 1× CPU fan + 1× CPU OPT + 1× AIO pump + 4× chassis fan headers
• 3× Addressable Gen 2 (ARGB) headers — Aura Sync compatible
• Thunderbolt/USB4 header, S/PDIF out header, SPI TPM header
• BIOS FlashBack button (no CPU/RAM required)
• ASUS Q-LED Core debug LEDs (CPU/DRAM/VGA/BOOT)
• ASUS 5X Protection III (overvoltage protection, SafeSlot core+, stainless steel I/O)
• No PCIe Gen5 M.2 — top M.2 speed is PCIe 4.0 x4

 

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