ASUS PRIME B850M-A-CSM AMD B850 Socket AM5 micro ATX

Manufacturer: Asus | Model: 90MB1LQ0-M0EAYC | Product ID: 2212
£164.65 (inc. VAT)
10 in stock
100% Money Back Guarantee - Risk Free

Product Technical Specification

Processor
Processor manufacturerAMD
Processor socketSocket AM5
Compatible processor seriesAMD Ryzen 7000 Series,AMD Ryzen 8000 Series,AMD Ryzen 9000 Series
Supported processor socketsSocket AM5
Memory
Supported memory typesDDR5-SDRAM
Number of memory slots4
Memory slots typeDIMM
Memory channelsDual-channel
ECC сompatibilityECC & non-ECC
Supported memory clock speed (max)8000
Maximum internal memory256
Unbuffered memoryYes
Maximum internal memory per slot64
Storage controllers
Supported storage drive typesHDD & SSD
Supported storage drive interfacesPCI Express 4.0,PCI Express 5.0
Number of HDDs supported4
Number of storage drives supported7
RAID supportYes
RAID levels0,1,5,10
Graphics
Parallel processing technology supportNot supported
Maximum resolution7680 x 4320
Internal I/O
USB 2.0 connectors2
USB 3.2 Gen 1 (3.1 Gen 1) connectors2
Number of SATA III connectors4
S/PDIF out connectorYes
Front panel audio connectorYes
Front panel connectorYes
ATX Power connector (24-pin)Yes
CPU fan connectorYes
Number of CPU fan connectors1
Number of chassis fan connectors3
Chassis intrusion connectorYes
Peripheral (Molex) power connectors (4-pin)1
EPS power connector (8-pin)Yes
Number of EPS power connectors (8-pin)1
Number of COM connectors1
TPM connectorYes
12V power connectorYes
RGB LED pin headerYes
Number of RGB LED pin headers3
Rear panel I/O ports
USB 2.0 ports quantity4
USB 3.2 Gen 1 (3.1 Gen 1) Type-A ports quantity2
USB 3.2 Gen 2 (3.1 Gen 2) Type-A ports quantity2
Ethernet LAN (RJ-45) ports1
HDMI ports quantity1
HDMI version2.1
DisplayPorts quantity2
DisplayPort version1.4
Headphone outputs1
Line-inYes
Microphone inYes
Network
Ethernet LANYes
Ethernet interface type2.5 Gigabit Ethernet
Wi-FiNo
Features
Motherboard chipsetAMD B850
Audio output channels7.1
Product colourGrey
Component forPC
Motherboard form factorMicro ATX
Motherboard chipset familyAMD
Cooling typePassive
Power source typeATX
Windows operating systems supportedWindows 10 x64,Windows 11
Expansion slots
PCI Express x16 (Gen 4.x) slots2
PCI Express x16 (Gen 5.x) slots1
Number of M.2 (M) slots3
1st M.2 largest key size2280
1st M.2 highest PCI Express generation5.0
2nd M.2 largest key size2280
2nd M.2 highest PCI Express generation4.0
3rd M.2 largest key size2280
3rd M.2 highest PCI Express generation4.0
4th M.2 largest key size2280
4th M.2 highest PCI Express generation4.0
BIOS
BIOS typeUEFI AMI
BIOS memory size256
Packaging data
Package width275
Package depth275
Package height67.5
Package weight1450
Weight & dimensions
Width244
Depth244
Packaging content
Cables includedSATA
Screws includedYes

Delivery Options

Economy Delivery
FREE
Economy Delivery

Economy Delivery (UK)

Estimated delivery date: Sun 07th Dec 2025 to Wed 10th Dec 2025
Business Express
£6.95
Business Express

Business Express

Estimated delivery date: Sat 06th Dec 2025 to Mon 08th Dec 2025
View all Delivery Options & International Rates
ASUS Prime series motherboards are expertly engineered to unleash the full potential of AMD Ryzen™ 9000 series processors. The PRIME B850M-A-CSM motherboard provides users and PC DIY builders with a range of performance optimizations via intuitive software and firmware features. It’s designed to be Advanced AI PC-ready, offering the power and connectivity needed for demanding AI applications.

ASUS Corporate Stable Model
ASUS Corporate Stable Model (CSM) is a commercial program designed to provide stable and reliable motherboards. Offering up to 36-month product lifecycle support and 6-month end-of-life notice to allow sufficient lead times for your organization to get ready for product transitions. Each purchase of an ASUS CSM motherboard comes with ASUS Control Center Express - server-grade IT management software.

ASUS Control Center Express
ASUS Control Center Express is an integrated IT monitoring and management software designed to deploy faster, simplify IT operations and improve productivity with comprehensive control and user-friendly functions. ASUS Control Center Express is compatible with over 100 ASUS motherboards to provide a high-quality, TCO-optimized solution for your business needs.

Optimize IT endpoint management
Designed to assist IT staff in monitoring and controlling devices within their corporate networks, and facilitate inventory checking in multiple locations remotely.

Automate IT maintenance
Allows IT staff to schedule automatic updates of the latest BIOS, software and utilities to specific or all devices at off-peak times, enhancing system stability and IT operational flexibility.

Securely manage all of endpoints
Securely manage endpoint configuration, portable storage access and PC software applications by enabling them to create grouping rules on individual devices.

Performance
AI Solutions
ASUS AI Solutions include AI Advisor as your technical expert with expertise in PC performance.

AI Advisor
ASUS AI Advisor allows users to explore the functionality and advanced features of ASUS motherboards in a simple and straightforward way.

Performance
Digital Power Design
PRIME B850M-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.

The multi-layered printed circuit board design quickly dissipates heat around the voltage regulators to improve overall system stability and provide the CPU with more overclocking headroom.

The Digi+ voltage-regulator module (VRM) delivers real-time control over voltage droop, automatically switching frequency and power-efficiency settings.

Enhanced Memory & Storage Performance
Enhanced DDR5 performance
Comprehensive memory tuning options are the cornerstone of PRIME motherboards. The PRIME B850M-A-CSM maximizes the potential of your DDR5 modules, from entry-level to extreme-speed kits.2
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 B850M-A-CSM offers extensive AMD Extended Profiles for Overclocking (EXPO™) support and a wide array of UEFI settings for further performance tweaks.

Three M.2 slots (up to 128 Gbps)
PRIME B850M-A-CSM offers a total of three M.2 slots, including one that supports data-transfer speeds of up to 128 Gbps via PCIe 5.0, and two that support PCIe 4.0. This enables quicker boot-up and app load times with OS or application drives.

Cooling
Cooler by design
The PRIME B850M-A-CSM motherboard is engineered with multiple onboard heatsinks and an array of hybrid fan headers to help ensure your rig stays cool and stable under intense workloads.

Smart Cooling precision

ASUS Fan Xpert 2+
ASUS Fan Xpert 2+ software provides comprehensive control over fans. An Auto-Tuning mode intelligently configures all parameters with a single click. There’s also an Extreme Quiet mode that reduces chassis fan speeds to below the default minimum to keep your system whisper-quiet when performing light tasks. Fans can also be controlled via the UEFI BIOS.

Cooler compatibility
ASUS AIO coolers offer robust performance, high overclocking potential, bold aesthetics and customizable functionality for new motherboards, empowering you to build your dream gaming rig.

Flexibility
Empowering connections
This motherboard offers a versatile range of connectivity, including support for PCIe 5.0 slot and an arsenal of USB ports which includes Type-C® connections.

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.

Customization
Personalization
The PRIME B850M-A-CSM enhances the user experience across the board, from simplifying BIOS setting adjustments to offering customizable RGB lighting controls for a uniquely personal system aesthetic.

UEFI BIOS
The UEFI interface delivers easy-to-use configuration options for PC beginners, and advanced features for veterans.

ASUS DriverHub
Simplify driver management with automatic detection, one-click installation and update for smooth, efficient system performance.

Armoury Crate
Customize Aura Sync RGB and control ASUS devices. Includes product registration and updates.

Aura Sync
Complete RGB lighting control for enthusiast systems, ensuring seamless synchronization with compatible hardware.

Addressable Gen 2 RGB headers
Three addressable Gen 2 headers detect LED counts on compatible RGB devices, automatically adjusting lighting effects accordingly.

Customization
DIY friendly
The PRIME B850M-A-CSM motherboard features EZ PC DIY innovations that simplify and speed up the PC building process, making DIY easy and convenient.

Pre-mounted I/O shield
Our pre-installed I/O shield safeguards ports, simplifies the build process, increases functionality and enhances aesthetics for PC DIY enthusiasts.

BIOS FlashBack™
BIOS FlashBack™ simplifies BIOS updates. Just load the BIOS file onto a FAT32 USB stick, insert it into the BIOS FlashBack™ port, and press a button—no CPU or memory needed.

SafeSlot
PCIe 5.0 is twice as fast as PCIe 4.0. ASUS has adapted our SMT manufacturing for the faster SafeSlot, a reinforced metal sheath that ensures secure card installation and faster data speeds.

Q-LED Core
The Q-LED Core display produces color-coded lights during the Power-On Self-Test (POST) that can help you troubleshoot potential issues.

Build for the most advanced pc for gaming and creating
When only the fastest will do, ASUS motherboards deliver. With faster dual-channel DDR5 memory support, AMD EXPO™ technology and PCIe® 5.0 support for both graphics and NVMe, you can play the most demanding games and deliver your biggest projects with the revolutionary performance of an ASUS motherboard and AMD Ryzen™ 9000, 8000, and 7000 Series processors.
Processor
Processor manufacturerAMD
Processor socketSocket AM5
Compatible processor seriesAMD Ryzen 7000 Series,AMD Ryzen 8000 Series,AMD Ryzen 9000 Series
Supported processor socketsSocket AM5
Memory
Supported memory typesDDR5-SDRAM
Number of memory slots4
Memory slots typeDIMM
Memory channelsDual-channel
ECC сompatibilityECC & non-ECC
Supported memory clock speed (max)8000
Maximum internal memory256
Unbuffered memoryYes
Maximum internal memory per slot64
Storage controllers
Supported storage drive typesHDD & SSD
Supported storage drive interfacesPCI Express 4.0,PCI Express 5.0
Number of HDDs supported4
Number of storage drives supported7
RAID supportYes
RAID levels0,1,5,10
Graphics
Parallel processing technology supportNot supported
Maximum resolution7680 x 4320
Internal I/O
USB 2.0 connectors2
USB 3.2 Gen 1 (3.1 Gen 1) connectors2
Number of SATA III connectors4
S/PDIF out connectorYes
Front panel audio connectorYes
Front panel connectorYes
ATX Power connector (24-pin)Yes
CPU fan connectorYes
Number of CPU fan connectors1
Number of chassis fan connectors3
Chassis intrusion connectorYes
Peripheral (Molex) power connectors (4-pin)1
EPS power connector (8-pin)Yes
Number of EPS power connectors (8-pin)1
Number of COM connectors1
TPM connectorYes
12V power connectorYes
RGB LED pin headerYes
Number of RGB LED pin headers3
Rear panel I/O ports
USB 2.0 ports quantity4
USB 3.2 Gen 1 (3.1 Gen 1) Type-A ports quantity2
USB 3.2 Gen 2 (3.1 Gen 2) Type-A ports quantity2
Ethernet LAN (RJ-45) ports1
HDMI ports quantity1
HDMI version2.1
DisplayPorts quantity2
DisplayPort version1.4
Headphone outputs1
Line-inYes
Microphone inYes
Network
Ethernet LANYes
Ethernet interface type2.5 Gigabit Ethernet
Wi-FiNo
Features
Motherboard chipsetAMD B850
Audio output channels7.1
Product colourGrey
Component forPC
Motherboard form factorMicro ATX
Motherboard chipset familyAMD
Cooling typePassive
Power source typeATX
Windows operating systems supportedWindows 10 x64,Windows 11
Expansion slots
PCI Express x16 (Gen 4.x) slots2
PCI Express x16 (Gen 5.x) slots1
Number of M.2 (M) slots3
1st M.2 largest key size2280
1st M.2 highest PCI Express generation5.0
2nd M.2 largest key size2280
2nd M.2 highest PCI Express generation4.0
3rd M.2 largest key size2280
3rd M.2 highest PCI Express generation4.0
4th M.2 largest key size2280
4th M.2 highest PCI Express generation4.0
BIOS
BIOS typeUEFI AMI
BIOS memory size256
Packaging data
Package width275
Package depth275
Package height67.5
Package weight1450
Weight & dimensions
Width244
Depth244
Packaging content
Cables includedSATA
Screws includedYes

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Buykingston order despatch times:

We will despatch your order the very same day if we receive cleared payment by 12:00 pm Mon-Fri.

These delivery estimates apply when you order up to 12:00 pm Mon-Fri (excluding public holidays).

We charge a one off delivery cost as outlined below regardless of how many items you order or the weight of your order.

Estimated delivery times are provided to us by the respective delivery companies. We pass this information onto you, the customer.

Despatch times do not apply to UK public holidays.

Estimated delivery times are taken from the next available working day available for delivery. For example if an order was despatched on a working Wednesday by 3pm, the first available working day for delivery would be Thursday provided you placed your order by 3pm on the Wednesday. If the next available weekday is a UK bank holiday/public holiday then your order will be despatched on the next available working day.

Our warehouse reserves the right to upgrade the delivery method you select on your order.

Our available delivery options*

Contact us for a shipping quote.

*All delivery times are estimated unless stated.

Product Returns Note

Buykingston offers a very flexible and hassle free returns policy. If for whatever reason you are not happy with the item purchased you can return it to us within 12months for a refund (for unused and unopened items) or within 30 days on opened and used items for a refund. This applies to items purchased direct through Buykingston  only.

Our 30 Day Returns Money Back Guarantee Satisfaction Guarantee:
For items opened and used and that are returned in a resellable condition.

Our 365 Day Returns Money Back Guarantee Satisfaction Guarantee:
For items that remain sealed and unused.

Some items are excluded from our moneyback guarantee unless they have developed a fault. These include;

- Headphones
- Earphones
- Custom made and designed products such as flash memory products with custom logo’s on them. E,g USB flash drives and memory cards with your own logo

Returns FAQs

What is your returns criteria?
On opened items 30 days from date of receipt or expected date of receipt on non tracked items.
On unopened items 365 days.

How do i go about returning my order?
Please contact us via our contact page with your order number where we will present you with an RMA number and returns label.

Do i need to contact you before returning my order?
Yes, to obtain an RMA number.

Does my item have to include its original packaging?
Yes for items that fall within our 30 day money back guarantee and our 365 day returns. Of course for faulty items we realise you may no longer have the packaging.

Who deals with the warranty on a faulty item?
We will. In some circumstances we may ask you to contact the manufacturer direct for assistance.

Please ensure you have read and comply in full with Section 11 & 13 of our terms and conditions which you can read here in full.