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ASUS · AM5 · B840

ASUS Prime B840M-A WiFi-CSM

ATX · DDR5 · 4 DIMMs · 8-phase VRM · 6E

Quality
52
VRM
25
Value
58
Amazon
$170
ASUS Prime B840M-A WiFi-CSM
View ASUS Prime B840M-A WiFi-CSM Gallery in high resolution
$170
Available Updated 3 days, 9 hours ago Prime FBA
Overall52.2
VRM25.0
Chipset73.0
Expansion / storage67.0
Connectivity51.0
Audio45.0
Quality / price58.3
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Written analysis

ASUS Prime B840M-A WiFi-CSM at a glance

The ASUS Prime B840M-A WiFi-CSM uses the ATX form factor, AM5 socket, and B840 chipset. This is a balanced mainstream platform: enough expansion and connectivity for a performance PC without paying only for flagship extras.

Memory support is DDR5 across 4 DIMM slots, with up to 256 GB and rated overclocked speeds up to 7600 MT/s. ECC modules are accepted, subject to CPU support. XMP / EXPO memory-profile support is recorded for easier tuning.

Best fit: a mainstream gaming, home, or office system with moderate expansion needs.

Power delivery

The calculated VRM score is 25.0, placing the power delivery in the basic class. The board lists 8 CPU power phases, 60 A power stages in a 8+2+1 layout. CPU power input is listed as 1. Keep it paired with lower-power processors and avoid sustained overclocked loads.

Expansion and storage

The expansion and storage score is 67.0: balanced . The platform supports PCIe 4.0. Physical expansion includes 3 ×16 slots.

On-board storage consists of 3 M.2 slots and 4 SATA ports. Supported M.2 lengths are listed as 2280, 2242, 2260. That is enough NVMe capacity for a multi-drive gaming or creator setup without immediately relying on an add-in card.

Connectivity and rear I/O

The connectivity score is 51.0, rated adequate . Wireless networking is Wi-Fi 6E ; wired networking is Realtek 2.5Gb Ethernet at up to 2500 Mbps. Bluetooth 5.3 is included. The recorded USB provision is 7 rear connections and 1 front-panel connections. The specification sheet below separates every USB speed and connector type.

Display connectivity includes HDMI 2.1, DisplayPort 1.4. These motherboard outputs require a processor with integrated graphics.

Audio

The audio score is 45.0. This is a standard onboard solution using Realtek® ALC892/ALC897. It covers normal gaming and communication; demanding headphones or production work still benefit from an external interface. The rear panel has 3 analogue jacks.

Buying verdict

Overall quality is 52.20, a mainstream result. The essential platform features are covered, while premium I/O and tuning extras are more selective.

At the recorded Amazon price, the quality-to-price score is 58.3—a balanced value for its feature class.

Board data

Full specifications

Platform, expansion, storage, rear I/O, internal headers, networking, audio, and board controls in one sheet.

General

Manufacturer
ASUS
Motherboard
ASUS Prime B840M-A WiFi-CSM
Chipset / socket
B840 / AM5
Form factor
ATX
Launch price
—
Amazon price
$170
Availability
In stock
Price updated
3 days, 9 hours ago

VRM

CPU phases
8 (60 A)
Power design
8+2+1
EPS connector
1

Memory

Type / slots
DDR5 / 4 DIMMs
Max capacity / OC
256 GB / 7600 MT/s
XMP / EXPO
Yes
ECC
Modules supported

PCIe

Supported version
PCIe 4.0
x16 physical
3
x16 Gen 4
1
x16 Gen 3
2

Storage

M.2 slots
3
M.2 lengths
2280, 2242, 2260
SATA ports
4

Display outputs

HDMI
Yes · 2.1 · 4K@60Hz
DisplayPort
Yes · 1.4 · 8K@30Hz
USB-C DisplayPort
No

USB

Rear USB 2.0
4
Rear USB 3.2 Gen 1 Type-C 5 Gbps
1
Rear USB 3.2 Gen 2 Type-A 10 Gbps
2
Front USB 3.2 Gen 1 Type-C 5 Gbps
1
Front USB-C PD
15 W
Header USB 2.0
4
Header USB 3.2 Gen 1 Type-A 5 Gbps
2

Networking

Ethernet
Realtek 2.5Gb Ethernet
LAN ports
1
LAN speed
2500 Mbps
Wi-Fi
6E
Bands
2.4/5/6GHz
Antenna connectors
2
Bluetooth
5.3

Audio

Chipset
Realtek® ALC892/ALC897
Analog jacks
3
Gold-plated jacks
No
Optical S/PDIF
No
Spatial audio
Rear output

Buttons

BIOS flashback
Yes
Clear CMOS
No
Q-Flash Plus
No
Smart button
No
Onboard start / reset
No

Additional information

Memory notes
Supports AMD Extended Profiles for Overclocking (EXPO™) and ASUS Enhanced Memory Profile (AEMP). Supports Un-buffered DIMMs. Supported memory types, data rate, and number of DRAM modules vary depending on the CPU and memory configuration. Non-ECC, un-buffered DDR5 memory supports On-Die ECC function.
Display notes
Graphics specifications may vary between CPU types. Please refer to AMD CPU specifications.
Expansion notes
The primary PCIe 4.0 x16 slot's operating mode depends on the installed CPU: it supports x16 mode with AMD Ryzen 9000 & 7000 Series, and x8/x4 mode with AMD Ryzen 8000 Series. The two PCIe 3.0 x16 slots from the chipset support x1 mode only. Refer to the manufacturer's support site for the PCIe bifurcation table.
M.2_1
4.0 4 · 2280 · CPU
M.2_2
4.0 4 · 2242, 2260, 2280 · CPU — The supported mode varies by CPU type. For AMD Ryzen 8000 Series Processors, it supports PCIe 4.0 x4/x2 mode. For Ryzen 9000 & 7000 Series, it supports PCIe 4.0 x4 mode.
M.2_3
3.0 4 · 2280 · Chipset
RAID
SATA / PCIe (0, 1, 5, 10)
Storage notes
AMD RAIDXpert2 Technology is supported. The available RAID levels depend on the CPU series: Ryzen 9000 supports RAID 0/1/5/10; Ryzen 7000 supports RAID 0/1/10; Ryzen 8000 supports RAID 0/1.
USB notes
Front USB Type-C® power delivery output: max. 5V/3A
Audio notes
Features Realtek 7.1 Surround Sound High Definition Audio CODEC with audio shielding, premium audio capacitors, and dedicated audio PCB layers. Supports jack-detection, multi-streaming, front panel jack-retasking, and up to 24-Bit/192 kHz playback. A chassis with an HD audio module in the front panel is required to support 7.1 Surround Sound audio output.
Networking notes
WiFi 6E 6GHz regulatory may vary between countries, supported only in Windows 11 or later. The Bluetooth® version may vary, please refer to the Wi-Fi module manufacturer's website for the latest specifications.
Button notes
The motherboard includes a Clear CMOS header, but not a dedicated button.
Fan / RGB headers
1 CPU · 1 OPT · 1 AIO · 3 chassis · 3 ARGB · — RGB
Other headers
Front audio · System panel · TPM
Dimensions
24.4cm x 24.4cm

Extracted notes sit here. Official manufacturer copy is at the bottom of the page.

Amazon

Price history

Nearby quality

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VRM fit

VRM-appropriate CPUs

AM5 processors whose TDP sits in this board’s VRM window. Socket match is required; chipset extras still matter on sTR5. This is a power-delivery filter, not a ranked CPU guide.

Open AM5 CPUs in the CPU table

Discussion

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Vendor copy

Official manufacturer data

Raw manufacturer text kept for reference. Structured specs above are extracted from this copy and are the source for scores and tables.

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

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

Internal I/O

Fan and Cooling Related
1 x 4-pin CPU Fan header
1 x 4-pin CPU OPT Fan header
1 x 4-pin AIO Pump header
3 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

Rear I/O

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 Wi-Fi module
1 x Realtek 2.5Gb Ethernet port
3 x Audio jacks
1 x BIOS FlashBack™ button

Wireless

Wi-Fi 6E
2x2 Wi-Fi 6E (802.11ax)
Supports 2.4/5/6GHz frequency band*
Bluetooth® v5.3**
* WiFi 6E 6GHz regulatory may vary between countries, supported only in Windows 11 or later.
** The Bluetooth® version may vary, please refer to the Wi-Fi module manufacturer's website for the latest specifications.

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.

Special features

ASUS 5X PROTECTION III
- DIGI+ VRM
- LANGuard
- Overvoltage protection
- SafeSlot Core+
- Stainless-steel back I/O
ASUS Q-Design
- Q-Antenna
- 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

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