Asus Prime B850M-K-CSM M-ATX Motherboard
MPN PRIME-B850M-K-CSM · Brand ASUS · mATX
ASUS Prime B850M-K-CSM is a Micro-ATX motherboard with AM5 socket, AMD B850 chipset, DDR5 support up to 8400+ MT/s, PCIe 5.0, dual M.2, 2.5 Gb LAN, and 3-year warranty — compatible with AMD Ryzen 9000, 8000, and 7000 series processors
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Overview
The ASUS Prime B850M-K-CSM is a Micro-ATX motherboard built on the AMD B850 chipset with an AM5 socket, designed to support AMD Ryzen 9000, 8000, and 7000 series desktop processors. Engineered for both PC builders and commercial system integrators (CSM), it delivers a thoughtful mix of performance features, reliable thermal management, and broad connectivity in a compact form factor. Power delivery is handled by an 8+2+1 phase digital power design using discrete MOSFETs, providing stable and efficient voltage regulation for AMD processors under everyday and sustained workloads. The included VRM heatsink with thermal pad draws heat away from the MOSFETs and chokes, complemented by a passive aluminium chipset heatsink that avoids the long-term reliability concerns associated with fan-cooled alternatives. Memory support covers dual-channel DDR5 with speeds up to 8400+ MT/s (OC), with a maximum capacity of 128 GB across two DIMM slots. Both ASUS Enhanced Memory Profile (AEMP) and AMD Extended Profiles for Overclocking (EXPO) are supported, allowing straightforward one-click memory speed optimisation without manual BIOS tuning. Storage is handled by two M.2 Key-M slots: one operating at PCIe 5.0 for transfers up to 128 Gbps, and one at PCIe 4.0. Four SATA 6 Gb/s ports provide additional drive connectivity. The primary PCIe x16 slot runs at PCIe 5.0 x16 mode with Ryzen 9000 and 7000 processors, supporting the latest discrete graphics cards. Networking is provided by a Realtek 2.5 Gb Ethernet controller for fast, low-latency wired connectivity. The rear panel includes 2× USB 10 Gbps Type-A, 2× USB 5 Gbps Type-A, 4× USB 2.0 Type-A, DisplayPort, HDMI, a 3.5 mm audio jack array, BIOS FlashBack button, and a PS/2 combo port. Internal headers add a front-panel USB Type-C (5 Gbps), additional USB 5 Gbps and USB 2.0 headers, three Addressable RGB Gen 2 headers, and fan headers for a 4-pin CPU fan and three 4-pin chassis fans. Fan control is managed through Fan Xpert 2+, which allows per-header temperature source mapping across CPU, chassis, and supported GPU sensors. The M.2 heatsink prevents NVMe throttling during sustained sequential transfers. A SPI TPM header (14-1 pin), COM port header, Clear CMOS header, S/PDIF out, and Front Panel Audio header round out the internal connector set. --- Verified Specifications --- Socket: AM5 | Chipset: AMD B850 | Form Factor: Micro-ATX CPU Support: AMD Ryzen 9000 / 8000 / 7000 Series Memory: DDR5 Dual Channel, up to 128 GB, up to 8400+ MT/s (OC), EXPO & AEMP supported Primary PCIe Slot: 1× PCIe 5.0 x16 (Ryzen 9000/7000); PCIe 4.0 x8/x4 (Ryzen 8000) Chipset Slot: 1× PCIe 4.0 x16 (x4 mode) M.2 Slots: 2× Key-M (1× PCIe 5.0 up to 128 Gbps; 1× PCIe 4.0) SATA: 4× SATA 6 Gb/s LAN: Realtek 2.5 Gb Ethernet Display Output: 1× HDMI, 1× DisplayPort Rear USB: 2× USB 10 Gbps (Type-A), 2× USB 5 Gbps (Type-A), 4× USB 2.0 (Type-A) ARGB Headers: 3× Addressable RGB Gen 2 Warranty: 3 Years
Datasheet
| Memory Type | DDR5 |
|---|---|
| Warranty | 3 Years |
| Form Factor | mATX |
| Chipset | B850 |
| Socket | AM5 |
| CPU Type | Ryzen 9000,Ryzen 8000,Ryzen 7000 |
| Max Memory | 128 GB |
| Memory Speed | up to 8400+ |
| Platform | AMD |
| Graphics Port | 1x HDMI,1x DisplayPort |
| Memory Feature | Supports AMD Extended Profiles for Overclocking (EXPO) ASUS Enhanced Memory Profile (AEMP) * Supported memory types, data rate (speed), and number of DRAM modules vary depending on the CPU and memory configuration, for more information please refer to CPU/Memory Support list under the Support tab of product information site or visit https://www.asus.com/support/download-center/. Adjustments will be made based on the specifications of mass-produced memory products available on the market. * Non-ECC, un-buffered DDR5 memory supports On-Die ECC function |
| Expansion Slots | AMD 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)** AMD B850 Chipset 1 x PCIe 4.0 x16 slot (support x4 mode) * Please check the PCIe bifurcation table on the support site (https://www.asus.com/support/FAQ/1037507/). ** Specifications vary by CPU types. – To ensure compatibility of the device installed, please Visit to https://www.asus.com/support/download-center/ for the list of supported |
| Channel Supported | Dual Channel |
| Back Panel I/O Ports | 2 x USB 10Gbps ports (2 x Type-A) 2 x USB 5Gbps ports (2 x Type-A) 4 x USB 2.0 ports (4 x Type-A) 1 x DisplayPort 1 x HDMI port 1 x Realtek 2.5Gb Ethernet port 3 x Audio jacks 1 x BIOS FlashBack button 1 x PS/2 Keyboard/Mouse combo port |
| Internal I/O Connector | Fan and Cooling Related 1 x 4-pin CPU Fan header 3 x 4-pin Chassis Fan headers Power Related 1 x 24-pin Main Power connector 1 x 8-pin +12V CPU Power connector Storage Related 2 x M.2 slots (Key M) 4 x SATA 6Gb/s ports USB 1 x USB 5Gbps connector (supports USB Type-C) 1 x USB 5Gbps header supports 2 additional USB 5Gbps ports 2 x USB 2.0 headers support 4 additional USB 2.0 ports Miscellaneous 3 x Addressable RGB Gen 2 headers 1 x Clear CMOS header 1 x COM Port header 1 x Front Panel Audio header (F_AUDIO) 1 x S/PDIF Out header 1 x SPI TPM header (14-1 pin) 1 x 10-1 pin System Panel header |
