ASUS Prime B840M-A-CSM DDR5 LGA1851 Motherboard
Available Colors
Asus ( ASUS Prime B840M-A-CSM DDR5 LGA1851 Motherboard )
Digital Power Design
PRIME B840M-A-CSM features an 8+2+1 phase power design with discrete MOSFETs, ensuring efficient and stable power delivery for AMD processors plus steady performance for day-to-day use.5
8 Vcore power
2 SOC power
1 Misc power
Enhanced DDR5 performance
Comprehensive memory tuning options are the cornerstone of PRIME motherboards. The PRIME B840M-A-CSM maximizes the potential of your DDR5 modules, from entry-level to extreme-speed kits.*
For entry-level modules without EXPO™ support, ASUS Enhanced Memory Profile (AEMP) automatically detects memory chips and provides optimized profiles for enhanced performance.
For those looking to surpass stock DDR5 speeds, the PRIME B840M-A-CSM offers extensive AMD Extended Profiles for Overclocking (EXPO™) support and a wide array of UEFI settings for further performance tweaks.**
*Memory overclocking may vary between CPU series. Please refer to the spec table for detailed information.
**Supported memory types, data rates (speed), and number of DRAM modules vary depending on the CPU and memory configuration. For more information, please refer to the CPU/Memory Support List under the Support tab on the product information page or visit https://www.asus.com/support/download-center/.
Three M.2 slots (up to 64 Gbps)
PRIME B840M-A-CSM offers a total of three M.2 slots, including two that support data-transfer speeds of up to 64 Gbps via PCIe 4.0, and one that supports PCIe 3.0. This enables quicker boot-up and app load times with OS or application drives.*
*Actual transmission speeds will be lower than the theoretical maximum speed.
Realtek 2.5 Gb Ethernet
Realtek 2.5 Gb Ethernet reduces CPU overhead and offers exceptionally high TCP and UDP throughput for faster, smoother data transfers.
Front USB 5Gbps Type-C®
This motherboard features a USB 5Gbps Type-C® front panel connector for speedy data transfers of up to 5Gbps.*
*Image(s) for reference only.
Asus ( ASUS Prime B840M-A-CSM DDR5 LGA1851 Motherboard )
Model
PRIME B840M-A-CSM
News & Updates
Please visit our GLOBAL website to check and download the latest updates.
CPU
AMD Socket AM5 for AMD Ryzen™ 9000 & 8000 & 7000 Series Desktop Processors*
* Refer to https://www.asus.com/support/download-center/ for CPU support list.
Chipset
AMD B840 Chipset
Memory
4 x DIMM slots, max. 256GB, DDR5
Supports up to 7600+MT/s (OC) with Ryzen™ 9000 & 8000 & 7000 Series Processors, ECC and Non-ECC, Un-buffered DIMM*
Dual channel memory architecture
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.
Graphics
2 x DisplayPort**
1 x HDMI™ port***
* Graphics specifications may vary between CPU types. Please refer to AMD CPU specifications.
** Supports max. 8K@30Hz as specified in DisplayPort 1.4.
*** Supports 4K@60Hz as specified in HDMI 2.1.
Expansion Slots
AMD Ryzen™ 9000 & 7000 Series Desktop Processors*
1 x PCIe 4.0 x16 slot (supports x16 mode)
AMD Ryzen™ 8000 Series Desktop Processors
1 x PCIe 4.0 x16 slot (supports x8/x4 mode)**
AMD B840 Chipset
2 x PCIe 3.0 x16 slots (support x1 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 refer to https://www.asus.com/support/download-center/ for the list of supported peripherals.
Storage
Total supports 3 x M.2 slots and 4 x SATA 6Gb/s ports
AMD Ryzen™ 9000 & 7000 Series Desktop Processors
M.2_1 slot (Key M), type 2280 (supports PCIe 4.0 x4 mode)
M.2_2 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4 mode)
AMD Ryzen™ 8000 Series Desktop Processors
M.2_1 slot (Key M), type 2280 (supports PCIe 4.0 x4 mode)
M.2_2 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4/x2 mode)*
AMD B840 Chipset
M.2_3 slot (Key M), type 2280 (supports PCIe 3.0 x4 mode)
4 x SATA 6Gb/s ports
* Specifications vary by CPU types.
AMD RAIDXpert2 Technology
Ryzen™ 9000 Series Processors: RAID 0/1/5/10
Ryzen™ 8000 Series Processors: RAID 0/1
Ryzen™ 7000 Series Processors: RAID 0/1/10
Ethernet
1 x Realtek 2.5Gb Ethernet
ASUS LANGuard
USB
Rear USB (Total 7 ports)
2 x USB 10Gbps ports (2 x Type-A)
1 x USB 5Gbps port (1 x USB Type-C®)
4 x USB 2.0 ports (4 x Type-A)
Front USB (Total 7 ports)
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
* USB Type-C® power delivery output: max. 5V/3A
Audio
Realtek 7.1 Surround Sound High Definition Audio CODEC*
- Supports: Jack-detection, Multi-streaming, Front Panel Jack-retasking
- Supports up to 24-Bit/192 kHz playback
Audio Features
- Audio Shielding
- Premium audio capacitors
- Dedicated audio PCB layers
* A chassis with an HD audio module in the front panel is required to support 7.1 Surround Sound audio output.
Back Panel I/O Ports
2 x USB 10Gbps ports (2 x Type-A)
1 x USB 5Gbps port (1 x USB Type-C®)
4 x USB 2.0 ports (4 x Type-A)
2 x DisplayPort
1 x HDMI™ port
1 x Realtek 2.5Gb Ethernet port
3 x Audio jacks
1 x BIOS FlashBack™ button
Internal I/O Connectors
Fan and Cooling Related
1 x 4-pin CPU Fan header
1 x 4-pin CPU OPT Fan header
2 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
3 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 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 Front Panel System header
Special Features
ASUS 5X PROTECTION III
- DIGI+ VRM
- LANGuard
- Overvoltage protection
- SafeSlot Core+
- Stainless-steel back I/O
ASUS Q-Design
- Q-Dashboard
- Q-DIMM
- Q-LED Core
- Q-Slot
ASUS Thermal Solution
- M.2 heatsink
- VRM heatsink design
ASUS EZ DIY
- BIOS FlashBack™ button
- BIOS FlashBack™ LED
- Pre-mounted I/O shield
Aura Sync
- Addressable Gen 2 headers
Software Features
ASUS Exclusive Software
Armoury Crate
- Aura Creator
- Aura Sync
- Fan Xpert 2+
- Power Saving
ASUS DriverHub
TurboV Core
ASUS CPU-Z
Norton 360 Deluxe (60 Days Free Trial)
WinRAR (40 Days Free Trial)
UEFI BIOS
ASUS EZ DIY
- ASUS CrashFree BIOS 3
- ASUS EZ Flash 3
- ASUS UEFI BIOS EZ Mode
- ASUS MyHotkey
Remote Management Features
IT Management software supported
- ASUS Control Center Express (ACCE)
BIOS
256 Mb Flash ROM, UEFI AMI BIOS
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