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ASUS PRIME B850M-K mATX motherboard with AMD Ryzen 9 9900X CPU in AM5 socket

ASUS

ASUS PRIME B850M-K AMD motherboard & Ryzen 9 9900X CPU combo

SKU CH-028G-121ME

Pairs a B850 micro-ATX board with a 12-core 24-thread Ryzen 9 9900X CPU reaching 5.6 GHz boost, plus DDR5 8400 MT/s support, PCIe 5.0, three M.2 slots and 2.5 Gb Ethernet

  • CPU socketAM5

Motherboard PRIME B850M-K

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CPU + Ryzen 9 9900X

  • 12-core Ryzen 9 9900X CPU delivers 5.6 GHz max boost for heavy workloads
  • DDR5 memory scales to 8400 MT/s overclocked for high bandwidth
  • Three M.2 slots provide up to 128 Gbps total storage throughput
  • Realtek 2.5 Gb Ethernet plus rear USB 10 Gbps Type-A for fast wired connectivity
  • 8+2+1 power modules on a 6-layer PCB with Digi+ VRM ensure stable power delivery

Combo motherboard and CPU

This bundle pairs an ASUS PRIME B850M-K motherboard with a Ryzen 9 9900X processor. The board uses the AM5 socket and a 6-layer PCB with 8+2+1 power modules. The CPU delivers 12 cores and 24 threads based on Zen 5 architecture with a 5.6 GHz max boost clock.

Suits high-performance builds

Builders who want a ready-matched platform for demanding workloads benefit from the combined DDR5 8400 MT/s overclocking headroom and PCIe 5.0 slot support. Users needing integrated Wi-Fi or a bundled cooler should consider other options as neither is included here.

DDR5 8400 MT/s overclocking ceiling

The motherboard supports memory speeds up to DDR5 8400 MT/s when overclocked, while the processor officially supports DDR5 5600. This gap determines whether your memory kit can run at its rated XMP or EXPO profile without manual tuning.

How it compares

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

Price $626.99
Pricier than about 71% of the 1,906 comparable items (median $224.49).

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Specifications

Product
Brand nameASUS
Model namePRIME B850M-K+R9 9900X
Processor
CPU socketAM5

Other versions of this model

5 more in the same range

Questions about this item

Does the box include a CPU cooler for the Ryzen 9 9900X?

The supplier description states the cooler is not included, so a separate AM5-compatible cooler must be purchased.

Which DDR5 speed should I target for the Ryzen 9 9900X on this board?

The CPU officially supports DDR5-5600 while the motherboard can reach DDR5 8400+ MT/s when overclocked; choose a kit rated for 5600 MT/s or higher.

What does the 5.6 GHz max boost mean for everyday workloads?

The 12-core, 24-thread processor can hit 5.6 GHz on lightly threaded tasks, delivering strong single-thread responsiveness while the 64 MB L3 cache helps multi-thread throughput.

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