Asus Prime B840M-A-CSM AMD AM5

Description

Corporate-Grade AM5 Stability in Micro-ATX

The Prime B840M-A-CSM is part of ASUS’s Corporate Stable Model (CSM) programme, which means it carries commitments that go beyond a standard retail board: up to 36 months of product lifecycle support, a 6-month end-of-life notice to allow procurement planning, and ASUS Control Center Express (ACCE) IT management software included in the box. This makes it the most appropriate choice in the B840M-A family for businesses deploying multiple units, IT administrators managing fleets, or any buyer who needs documented lifecycle stability rather than just a motherboard spec sheet. The hardware itself is identical in core capability to the non-CSM variant — 8+2+1 phase discrete MOSFET power design with DIGI+ VRM, 170W CPU support, VRM heatsink, SafeSlot Core+ reinforced GPU slot, stainless steel I/O, and premium audio with dedicated PCB layers and audio shielding.

⚠️ The B840 chipset does not support CPU overclocking. Memory overclocking via AMD EXPO and ASUS AEMP profiles is supported up to DDR5-7600+ (OC). If CPU OC is a requirement, B850 is the step up.

⚠️ No Wi-Fi module is included — this is the wired-only CSM variant. If onboard wireless is needed, the Prime B840M-A WiFi or B840M-A WiFi-CSM are the appropriate alternatives.

Memory and Storage

Four DDR5 DIMM slots support dual-channel operation up to 256 GB, with AMD EXPO and ASUS AEMP profile support reaching DDR5-7600+ (OC). The three M.2 slots mirror the B840M-A WiFi layout: M2_1 is CPU-connected at PCIe 4.0 x4 (64 Gb/s) in 2280, M2_2 is CPU-connected at PCIe 4.0 x4 (64 Gb/s) and supports 2242 and 2260 form factors in addition to 2280, and M2_3 is chipset-connected at PCIe 3.0 x4 (32 Gb/s) in 2280. All three slots are covered by M.2 heatsinks. Four SATA 6Gb/s ports are available alongside. RAID support is CPU-generation dependent: RAID 0/1/5/10 on Ryzen 9000, RAID 0/1/10 on Ryzen 7000, and RAID 0/1 only on Ryzen 8000.

⚠️ M2_2 drops from PCIe 4.0 x4 to x2 with Ryzen 8000 Phoenix 2 processors. Ryzen 7000 and 9000 run both CPU-connected M.2 slots at the full PCIe 4.0 x4 rate.

⚠️ No PCIe Gen5 M.2 is present — the fastest M.2 tier is PCIe 4.0 x4 (64 Gb/s). B850 or X870 is required for Gen5 NVMe speeds.

Connectivity and I/O

The rear I/O is identical to the B840M-A WiFi: dual DisplayPort 1.4 (up to 8K 30Hz each) plus HDMI 2.1 (4K 60Hz) for iGPU-equipped processors, two USB 10 Gbps Type-A, one USB 5 Gbps Type-C, and four USB 2.0 Type-A — seven rear USB ports total. Realtek 2.5G LANGuard Ethernet handles wired networking. Front panel USB is well covered with a USB 5 Gbps Type-C header and a standard 5 Gbps header supporting two additional ports. Fan headers consist of one CPU fan, one CPU OPT fan, and two chassis fan headers — one fewer than the WiFi variant, which includes an AIO pump header. Three Addressable Gen 2 (ARGB) headers enable Aura Sync RGB lighting control. Additional internal headers include S/PDIF out, COM port, and SPI TPM for enterprise and specialist deployment needs. Wake-on-LAN and PXE boot are supported for remote management workflows.

⚠️ The primary PCIe 4.0 x16 GPU slot drops to x8/x4 mode with Ryzen 8000 Series processors. The two chipset-side PCIe 3.0 x16 slots run at x1 mode only — suitable for network adapters, capture cards, and similar low-bandwidth expansion cards.

⚠️ No AIO pump header is present on this board — only two chassis fan headers and one CPU OPT header are available beyond CPU_FAN1. If an AIO liquid cooler is planned, connect the pump to the CPU OPT header and verify your cooler supports this configuration.

⚠️ 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
• ASUS Corporate Stable Model (CSM) — up to 36-month lifecycle support
• ASUS Control Center Express (ACCE) IT management software included
• Micro-ATX form factor — 244 mm × 244 mm
• 8+2+1 phase power design, discrete MOSFETs, DIGI+ VRM
• Single 8-pin ATX12V CPU power connector
• 4× DDR5 DIMM slots, dual-channel, up to 256 GB, DDR5 7600+ (OC)
• AMD EXPO and ASUS AEMP memory profile support
• 1× M.2 PCIe 4.0 x4 (CPU, 64 Gb/s, 2280) — M2_1, with heatsink
• 1× M.2 PCIe 4.0 x4 (CPU, 64 Gb/s, 2242/2260/2280) — M2_2, with heatsink
• 1× M.2 PCIe 3.0 x4 (chipset, 32 Gb/s, 2280) — M2_3, with heatsink
• 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, SafeSlot Core+) + 2× PCIe 3.0 x16 (x1 mode, chipset)
• Dual DisplayPort 1.4 (up to 8K 30Hz each) + HDMI 2.1 (4K 60Hz) — rear
• Realtek 2.5G Ethernet with ASUS LANGuard
• No onboard Wi-Fi — wired-only
• 2× rear USB 10 Gbps Type-A + 1× rear USB 5 Gbps Type-C + 4× USB 2.0 Type-A
• Front USB 5 Gbps Type-C header + 5 Gbps header (2 ports)
• 1× CPU fan + 1× CPU OPT + 2× chassis fan headers (no AIO pump header)
• 3× Addressable Gen 2 (ARGB) headers — Aura Sync compatible
• S/PDIF out header, SPI TPM header, COM port header
• Wake-on-LAN (WOL) and PXE boot support
• 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

 

Proudly sold by the Ringwood Digital Store.