Skip to main contentSkip to footer
1 of 5

Overview

PRO B840M-B is engineered with many exclusive features of MSI, PCIe 4.0 M.2, EZ PCIe Clip II, 2.5G LAN, and Front Type-C, ready for the AMD Ryzen™ 9000 series processors.

MSI PRO B840M-B Motherboard, mATX - Supports AMD Ryzen 9000/8000 / 7000 Processors, AM5 - DDR5 Memory Boost (8000+ MT/s OC), PCIe 4.0 x16, M.2 Gen4, Wi-Fi 7, 2.5G LAN

Model: PROB840MB
Web Code: 19504342
Sold and shipped by | 4.6 seller rating (247 reviews)

Available for deliveryAvailable online only

Delivery times vary by location. Most Marketplace items leave sellers' locations within 2 business days. Allow additional time for shipping.

Enjoy on orders from this seller.

Seller Return Policy

Warranty

Check with the manufacturer for details.

For Quebec residents: See the Availability Guarantee disclosure in the Specifications section below.

PRO B840M-B

Supports AMD Ryzen™ 9000 / 8000 / 7000 Series Desktop Processors

Supports DDR5 Memory, Dual Channel DDR5 8000+ MT/s (OC)

Ultra Performance: Direct 7+2+1 Power System with P-PAK, 8-pin CPU power connector, Core Boost, Memory Boost, 6-layer PCB made by 2oz thickened copper

EZ DIY: EZ M.2 Clip II and EZ PCIe Clip II

Lightning Fast Game experience: PCIe 4.0 slot and Lightning Gen 4 x4 M.2

2.5G LAN: the remarkable solution for professional and multimedia use, delivering secure, stable, and high-speed networking and data transmission

Audio Boost: Reward your ears with studio grade sound quality for the most immersive gaming experience

Product Condition
Brand New
Motherboard Form Factor
Micro-ATX
Year of Original Release
2025
CPU Socket Type
AM5
Processors Supported
AMD Ryzen 9000/8000/7000 Series
Supported Processor Chipset Make
AMD
Chipset
AMD B840
Memory Channel Architecture
Dual Channel
Computer RAM Type
DDR5
Memory Supported
DDR5
RAM Pin Configuration
288-Pin
Memory Slots
2
Maximum Memory Supported
128 GB
Built-in Audio
Yes
M.2 Slot
2
PCIe Generation
PCIe 4.0
PCI Express X1 Slots
1
PCI Express X4 Slots
0
PCI Express X8 Slots
0
PCI Express X16 Slots
1
Ethernet Port
1
USB 2.0 Ports
6
USB 3.0 Ports
7
USB 3.1 Ports
0
USB 3.1/3.2 Gen 2 Ports
0
HDMI Port
1
DVI Port
0
Other Video Ports
1x HDMI, 1x VGA
Other Audio Ports
Audio Connectors
SATA II 3.0Gb/s Ports
0
SATA III 6.0Gb/s Ports
4
Other Technologies
2.5G LAN, EZ Debug LED

For Quebec residents – Disclosure under the Consumer Protection Act

In compliance with Bill 29, Best Buy and third-party sellers on Best Buy Marketplace do not guarantee the availability of replacement parts, repair services, or maintenance information for any products. Coverage provided through any Best Buy Protection programs and applicable manufacturer warranties, if any, remain in place. Please contact the manufacturer directly for information about their availability guarantee.

Shipping Charges

Free standard shipping on all orders.

Processing Time

Most items ship within 2 business days after an order is placed*. Allow additional time for shipping to your address.
*Please note: If an item you ordered becomes unavailable, you'll be notified and a full refund will be processed within 2 business days.

Shipping Area Restrictions

Shipping is not available in the following areas*:
  • Quebec
*Please note: Shipping area restrictions may vary for large items. If an item can't be shipped to your address, we'll let you know during the checkout process.
Product Category
Computer components
Return/Exchange Period
30 days
Condition
Unopened

We can only acceept returns that are in their original packaging and do recommend customers check manufacturer's warranties for exclusions.

Learn more about returning a Marketplace product