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ASUS PRIME B850M-K mATX motherboard with Ryzen 7 9800X3D CPU in AM5 socket

ASUS

ASUS PRIME B850M-K AMD motherboard & Ryzen 7 9800X3D CPU Combo

SKU CH-KM9G-3QKTD

Socket AM5 motherboard and CPU combo with 8 cores, 16 threads, 96 MB L3 cache, 5.2 GHz boost, DDR5-8400 OC support, three M.2 slots up to 128 Gbps, PCIe 5.0 slot.

  • CPU Socket TypeAM5

Motherboard PRIME B850M-K

Struck-through versions exist but are not stocked here.

CPU + Ryzen 7 9800X3D

  • 8 cores and 16 threads deliver high gaming throughput
  • 96 MB L3 cache with 3D V-Cache cuts latency
  • DDR5 up to 8400 MT/s overclocking boosts memory bandwidth
  • Three M.2 slots provide up to 128 Gbps storage speed
  • Realtek 2.5 Gb Ethernet plus USB 10 Gbps Type-C gives fast connectivity

Combo foundation

The ASUS PRIME B850M-K motherboard pairs with an AMD Ryzen 7 9800X3D processor in a single package. The board uses the AM5 socket and the B850 chipset to support DDR5 memory and PCIe 5.0 devices. The CPU delivers 8 cores and 16 threads based on the Zen 5 architecture with a 5.2 GHz max boost clock and 96 MB of L3 cache. This combination targets builders who want a ready-to-run platform for gaming and multitasking.

Build integration

The micro-ATX board fits standard cases and supplies three M.2 slots with up to 128 Gbps total bandwidth for fast storage expansion. A Realtek 2.5 Gb Ethernet port handles wired networking while rear USB 10 Gbps Type-A and front USB 5 Gbps Type-C headers cover high-speed peripherals. The 8+2+1 power phase design on a 6-layer PCB with Digi+ VRM control feeds the processor cleanly. Four-pin PWM/DC fan headers and an M.2 heatsink manage component temperatures without extra hardware.

Sustained behaviour

The VRM heatsinks and thermal pads work with the board's smart fan protection to maintain stable voltage delivery during long gaming sessions. DDR5 memory can run at 8400 MT/s when overclocked while the CPU's 2nd-gen 3D V-Cache technology keeps latency low under continuous load. The 96 MB L3 cache and 8 MB L2 cache reduce memory pressure during extended workloads. UEFI BIOS and Aura Sync let you tune performance and lighting for consistent operation over time.

Highlights

  • 8 cores and 16 threads deliver high gaming throughput
  • 96 MB L3 cache with 3D V-Cache cuts latency
  • DDR5 up to 8400 MT/s overclocking boosts memory bandwidth
  • Three M.2 slots provide up to 128 Gbps storage speed
  • Realtek 2.5 Gb Ethernet plus USB 10 Gbps Type-C gives fast connectivity

Specifications

BrandASUS
ModelPRIME B850M-K+R7 9800X3D
CPU Socket TypeAM5

Other versions of this model

5 more in the same range

Same family, different memory, cooler or clock — compare before you commit.

Questions about this item

How much L3 cache does the Ryzen 7 9800X3D provide for sustained gaming workloads?

The processor includes 96MB of L3 cache using second-generation 3D V-Cache technology to reduce latency during extended gaming sessions.

What cooling capacity does the PRIME B850M-K offer when the system runs all day?

The board uses VRM heatsinks with thermal pads, an M.2 heatsink and a 4-pin PWM/DC fan header with smart protection to manage heat during continuous operation.

Which memory kit must I already own to reach the board's maximum DDR5 speed?

You need a DDR5 kit rated for 8400 MT/s or higher to achieve the motherboard's overclocked memory ceiling.

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