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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 Socket TypeAM5
  • ChipsetAMD B850
  • Number of Memory Slots2x288pin (DDR5)
  • Maximum Memory Supported96GB
  • Channel SupportedDual Channel
  • ECC SupportedYes

Motherboard ROG STRIX B850-I GAMING WIFI

Struck-through versions exist but are not stocked here.

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.

Highlights

  • 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

Specifications

BrandASUS
ModelROG STRIX B850-I GAMING WIFI+R9 9900X3D
CPU Socket TypeAM5
ChipsetAMD B850
Number of Memory Slots2x288pin (DDR5)
Maximum Memory Supported96GB
Channel SupportedDual Channel
ECC SupportedYes
Buffer SupportedUn-buffered
Memory FeatureDual channel memory architecture
Supports AMD Extended Profiles for Overclocking (EXPO)
ASUS Enhanced Memory Profile (AEMP)
PCI Express 5.0 x16AMD Ryzen 9000 & 7000 Series Desktop Processors
1 x PCIe 5.0 x16 slot(s)
PCI Express 4.0 x16AMD Ryzen 8000 Series Desktop Processors
1 x PCIe 4.0 x16 slot(s)
Serial ATA (SATA)2 x SATA 6Gb/s
M.2AMD 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 RAIDAMD RAIDXpert2 Technology supports both PCIe RAID 0/1/10 and SATA RAID 0/1
Audio ChipsetRealtek ALC4080
Audio 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
Max LAN Speed2.5Gbps
Wireless LANWi-Fi 802.11 be
BluetoothBluetooth 5.4
Back I/O Ports1 x USB 20Gbps port(s)
5 x USB 10Gbps port(s) (4 x Type-A + 1 x USB Type-C with DP Alt mode)
2 x USB 2.0 port(s) (2 x Type-A)
1 x HDMI port
1 x Wi-Fi module
1 x Intel 2.5Gb Ethernet port
3 x Audio jacks
1 x Optical S/PDIF out port
1 x BIOS FlashBack button
1 x Clear CMOS button
1 x FlexKey button
Onboard USB1 x USB 10Gbps connector (support(s) USB Type-C)
1 x USB 5Gbps header(s) support(s) 2 additional USB 5Gbps ports
1 x USB 2.0 header(s) support(s) 4 additional USB 2.0 ports
Other ConnectorsFan and Cooling Related
1 x 4-pin CPU Fan header(s)
1 x 4-pin AIO Pump header(s)
1 x 4-pin Chassis Fan header(s)
1 x Extra Flow Fan header(s)
Miscellaneous
2 x Addressable Gen 2 header(s)
1 x CPU Over voltage jumper
1 x Front Panel Audio header (F_AUDIO)
1 x 10-1 pin Front System Panel header
1 x Thermal Sensor header
Form FactorMini ITX
Dimensions (W x L)6.7" x 6.7"
Power Pin1 x 24-pin Main Power connector
1 x 8-pin +12V CPU Power connector
BIOS Feature256 Mb Flash ROM, UEFI AMI BIOS // UEFI AMI BIOS(text-based)
SoftwareROG Exclusive Software
- ROG CPU-Z
- Dolby Atmos
ASUS Exclusive Software
Armoury Crate
- AIDA64 Extreme (60 days free trial)
- Aura Creator
- Aura Sync
- GameFirst
- HWiNFO
- Power Saving
ASUS AI Advisor
ASUS DriverHub
ASUS GlideX
TurboV Core
Adobe Creative Cloud (Free Trial)
Norton 360 for Gamers (60 Days Free Trial)
WinRAR (40 Days Free Trial)
UEFI BIOS
AI Overclocking Guide
ASUS EZ DIY
- ASUS CrashFree BIOS 3
- ASUS EZ Flash 3
- ASUS UEFI BIOS EZ Mode
- ASUS MyHotkey
Windows 11Windows 11, Windows 10 64-bit
Windows 11 (22H2 later)
FeaturesExtreme Engine Digi+
- 5K Black metallic capacitors
ASUS Q-Design
- M.2 Q-Latch
- M.2 Q-Slide
- PCIe Slot Q-Release Slim (with PCIe SafeSlot)
- Q-Antenna
- Q-Dashboard
- Q-DIMM
- Q-LED (CPU [red], DRAM [yellow], VGA [white], Boot Device [yellow green])
- Q-Slot
ASUS Thermal Solution
- M.2 heatsink backplate
- VRM heatsink design
ASUS EZ DIY
- BIOS FlashBack button
- BIOS FlashBack LED
- Clear CMOS button
- ProCool
- Pre-mounted I/O shield
- SafeSlot
- SafeDIMM
Aura Sync
- Addressable Gen 2 header(s)
Package Contents1 x AMD Ryzen 9 9900X3D CPU
Cables
1 x Panel cable
1 x ROG USB2.0 splitter cable
2 x SATA 6Gb/s cables
Miscellaneous
1 x ASUS WiFi Q-Antenna
1 x Cable ties package
1 x M.2 backplate Q-Latch package(s)
1 x M.2 Q-Slide package
1 x ROG key chain
1 x M.2 backplate rubber package(s)
1 x Screw package(s) for M.2 SSD
Documentation
1 x Quick start guide

Other versions of this model

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

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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