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Compact Mini-ITX motherboard with large heatsinks and pre-mounted CPU

ASUS

ASUS ROG Strix B850-I Gaming WiFi AMD motherboard & Ryzen 9 9900X3D CPU combo

SKU CH-MPKX-BW4YB

A mini-ITX AM5 motherboard with 10+2+1 power stages and a 12-core Ryzen 9 9900X3D CPU featuring 128MB L3 cache and Radeon graphics

  • CPU socketAM5
  • ChipsetAMD B850
  • Form factorMini ITX
  • Memory slot count2 × 288pin (DDR5)
  • Max supported RAM96 GB
  • Memory channelsDual Channel

Motherboard ROG STRIX B850-I GAMING WIFI

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CPU + Ryzen 9 9900X3D

  • Ready for Ryzen 9000, 8000 and 7000 series CPUs via AM5 socket
  • 10+2+1 power stages rated 70A each with ProCool connectors for stable delivery
  • Dual PCIe 5.0 M.2 slots, one heatsinked, support 2242/2260/2280 drives
  • WiFi 7 and Intel 2.5Gbps Ethernet plus Bluetooth 5.4 for fast networking
  • 96GB DDR5 maximum across two slots with EXPO and AEMP support

Mini-ITX AM5 combo for compact high-performance

This bundle pairs the ROG Strix B850-I Gaming WiFi motherboard with the Ryzen 9 9900X3D processor. The board uses the AMD B850 chipset on a Mini-ITX form factor, delivering a full feature set in a small footprint. It targets enthusiasts building powerful small-form-factor systems for gaming or content creation. The included CPU brings 12 cores based on the Zen 5 architecture.

Dual DDR5 slots cap memory at 96 GB

Only two 288-pin slots are provided, limiting total capacity to 96 GB in dual-channel mode. The board supports AMD EXPO profiles and ASUS AEMP for automatic tuning of compatible DDR5 modules. ECC un-buffered memory is accepted, but the two-slot layout prevents expansion beyond the stated maximum. Builders needing more than 96 GB must choose a different platform.

128 MB L3 cache on the CPU drives gaming throughput

The Ryzen 9 9900X3D features 128 MB of L3 cache, a 12 MB L2 cache and integrated Radeon graphics within a 120 W TDP. This large last-level cache is the defining specification for latency-sensitive workloads and high-frame-rate gaming. The processor is fabricated on a TSMC 4 nm process and fits the AM5 socket shared by Ryzen 7000, 8000 and 9000 series chips.

How it compares

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

Price $1,180.99
Pricier than about 91% of the 1,906 comparable items (median $224.49).

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Specifications

Product
Brand nameASUS
Model nameROG STRIX B850-I GAMING WIFI+R9 9900 × 3D
Processor
CPU socketAM5
ChipsetAMD B850
Memory
Memory slot count2 × 288pin (DDR5)
Max supported RAM96 GB
Memory channelsDual Channel
ECC supportYes
BufferingUn-buffered
Storage
SATA ports2 x SATA 6Gb/s
M.2 slotsAMD Ryzen 9000 & 7000 Series Desktop Processors*
M.2_1 slot (Key M), type02242/2260/2280 (supports PCIe 5.0 x4 mode)
M.2_2 slot (Key M), type 2242/2260/2280 (supports PCIe 5.0 x4 mode)
AMD Ryzen 8000 Series Desktop Processors*
M.2_1 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4 mode)
M.2_2 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4 mode)
SATA and RAID supportAMD RAIDXpert2 Technology supports both PCIe RAID 0/1/10 and SATA RAID 0/1
Audio & video
Audio chipRealtek ALC4080
Sound channelsROG SupremeFX 7.1 Surround Sound High Definition Audio CODEC ALC4080*
- Impedance sense for front and rear headphone outputs
- Supports: Jack-detection, Multi-streaming, Front Panel MIC Jack-retasking
- High quality 120 dB SNR stereo playback output and 110 dB SNR recording input
- Supports up to 32-Bit/384 kHz playback on front panel
Audio Features
- SupremeFX Shielding Technology
- Savitech SV3H712 AMP
- Rear optical S/PDIF out port
- Premium audio capacitors
- Unique de-pop circuit
Connectivity
Maximum network speed2.5 Gbit/s
Wi-Fi standardWi-Fi 802.11 be
Bluetooth support5.4
Ports & slots
PCIe 5.0 x16 slotsAMD Ryzen 9000 & 7000 Series Desktop Processors
1 x PCIe 5.0 x16 slot(s)
PCIe 4.0 x16 slotsAMD Ryzen 8000 Series Desktop Processors
1 x PCIe 4.0 x16 slot(s)
Power
Power connectors1 × 24-pin Main Power connector
1 × 8-pin +12 V CPU Power connector
Size & build
Form factorMini ITX
Width and length6.7 in × 6.7 in
Compatibility
Windows 11 supportWindows 11, Windows 10 64-bit
Windows 11 (22H2 later)
More details
BIOS256 Mb Flash ROM, UEFI AMI BIOS // UEFI AMI BIOS(text-based)

Other versions of this model

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Questions about this item

Should I pick a 96 GB DDR5 kit or a smaller one for this board?

The board has two DDR5 slots and supports up to 96 GB in dual-channel mode, so a 96 GB kit occupies both slots fully.

What does the 128 MB L3 cache on the Ryzen 9 9900X3D do in real use?

The 128 MB L3 cache on the Ryzen 9 9900X3D reduces latency for gaming and heavy workloads by keeping more data close to the cores.

How fast can the PCIe 5.0 x16 slot and M.2 slots actually run?

The PCIe 5.0 x16 slot and both M.2 slots run at PCIe 5.0 speeds with Ryzen 9000 and 7000 series processors, while Ryzen 8000 series limits the x16 slot to PCIe 4.0.

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