ASUS PRIME B550-PLUS Upgrade Guide: RAM, SSD and CPU

Updated Oct. 9, 2026 · Written from this device's verified specifications

This guide covers adding memory, storage and a faster processor to the ASUS PRIME B550-PLUS, a socketed AM4 ATX motherboard with nothing soldered. The short version: it takes up to 128 GB of DDR4, two M.2 SSDs plus six SATA ports, and Ryzen 3000, 4000 G-series and 5000 CPUs up to 105 W, often after a BIOS update.

At a glance

  • RAM: 4 DDR4 DIMM slots, up to 128 GB total, dual-channel, unbuffered desktop modules only.
  • Storage: two M.2 slots (M.2_1 is PCIe 4.0 x4, M.2_2 is PCIe 3.0 x4) and six SATA 6Gb/s ports.
  • Using M.2_2 disables SATA ports 5 and 6, leaving four SATA ports.
  • CPU: AM4 socket, Ryzen 3000, 4000 G-series and 5000 series, up to 105 W.
  • Update the BIOS before fitting a newer CPU such as a 5700X3D, 5600X3D, 5800XT or 5900XT (BIOS 2803 or later).
DDR4 DIMM4 × DDR4 DIMM · up to 128 GB total · 4600 MT/s
M.2_1 (Key M, CPU)SSD M.2 2242 / M.2 2260 / M.2 2280 / M.2 22110 (NVMe / SATA)
M.2_2 (Key M, chipset)SSD M.2 2242 / M.2 2260 / M.2 2280 / M.2 22110 (NVMe / SATA)
SATA 6Gb/s port6 × HDD / SSD 2.5" / 3.5" (SATA)
AMD Socket AM4AM4 · Ryzen 3000, Ryzen 5000 · max 105 W
CPU · AM4max 105 W4 × DIMM · DDR4up to 128 GB totalM.2_1 (Key M, CPU)SSD M.2 2242 / M.2 2260 / M.2 2280 /M.2 22110 (NVMe / SATA)M.2_2 (Key M, chipset)SSD M.2 2242 / M.2 2260 / M.2 2280 /M.2 22110 (NVMe / SATA)SATA 6Gb/s port6 × HDD / SSD 2.5" / 3.5" (SATA)
Schematic of the upgradeable slots (not to scale). Check the owner's manual for their exact positions.

Lifecycle and support

A current model: sold new and supported.

20202021202220232024202520262027Today11 · Release · June 16, 2020
Filled dots: dates published by the manufacturer. Hollow dots: estimates from third-party sources.
MilestoneDate
Release
First available to buy.		 June 16, 2020 Estimate Inferred from the oldest BIOS on the ASUS support page (version 0608, dated 2020/06/16); the user manual is dated First Edition May 2020. ASUS gives no explicit launch date.
Source ↗

Dates not listed haven't been published by the manufacturer or a reliable third party.

Memory (RAM) upgrades

The board has four DDR4 DIMM sockets, two per channel (A1, A2, B1, B2), and runs dual-channel. Only full-size unbuffered desktop DIMMs fit. Laptop SO-DIMMs and registered server memory are not supported. ASUS lists a 128 GB maximum across the four slots. It doesn't state a per-module limit, but that total implies 32 GB per DIMM.

Only speeds up to 3200 MT/s run as standard. Anything faster relies on XMP or overclocking and isn't guaranteed. The original manual lists overclocked speeds up to 4400, while ASUS's newer spec page goes up to 4600, so the newer page is the better guide. ASUS also warns that the system may not reach the top supported speed because of platform limits.

Two matched DIMMs give the most stable setup. If you fit different amounts per channel, the board runs dual-channel up to the smaller channel's total and the rest runs single-channel. ECC support depends on the CPU: ASUS's documents differ on this, and the safe assumption is that ECC only works on CPUs that support it.

Buying tips

  • Buy unbuffered desktop DDR4 DIMMs, not SO-DIMM or registered modules.
  • Two matched modules or one matched kit is more stable than four.
  • Match CAS latency, and ideally the version or date code, if you add to existing memory.
  • Check your kit against ASUS's memory compatibility list. Some rows on that list look like errors, so verify the exact kit.
  • Expect to tune or drop speed if you fill all four slots with fast XMP memory.

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Storage upgrades (M.2 and SATA)

There are two M.2 Key M slots, and both take 2242, 2260, 2280 and 22110 drives in NVMe or SATA mode. M.2_1 is wired to the CPU and runs PCIe 4.0 x4 with 3rd Gen and 5000 series Ryzen. M.2_2 runs PCIe 3.0 x4 through the B550 chipset. Ryzen G-series APUs are likely limited to PCIe 3.0, and ASUS's newer spec text for those chips is unclear, so don't assume PCIe 4.0 with an APU.

The board also has six SATA 6Gb/s ports for 2.5 inch and 3.5 inch drives, with RAID 0, 1 and 10 support. Fitting a drive in M.2_2 disables SATA ports 5 and 6, leaving four usable ports. Drive bays and cables depend on your case, not the board. No maximum drive capacity is stated beyond the interface limits.

The x16 slots support PCIe bifurcation, so multi-NVMe adapter cards are an option. Note that the second x16 slot (PCIe 3.0, x4 speed) drops to x2 if PCIEX1_2 or PCIEX1_3 is occupied.

Buying tips

  • Put your fastest PCIe 4.0 SSD in M.2_1 and check your CPU supports PCIe 4.0.
  • Use M.2_2 for a PCIe 3.0 drive, and only if you can spare SATA ports 5 and 6.
  • A 22110 drive fits the slots, but check that your case and any cooler clear it.
  • Count the SATA drives you need before using both M.2 slots.
  • Check how many drive bays and SATA cables your case offers.

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CPU upgrades

The board uses a single AMD AM4 socket with the B550 chipset. The official list covers Ryzen 3000, 4000 G-series and PRO, and 5000 series processors, up to 105 W (for example the Ryzen 9 5950X). Ryzen 2000 chips are not on the official list. ASUS's BIOS notes mention Ryzen 2000 G-series, but don't rely on that.

Most newer CPUs need a BIOS update first. Ryzen 3000 parts need BIOS 0320. The Ryzen 5 5600X, 7 5800X and 9 5900X/5950X need 1004. Ryzen 5000 G-series APUs need 1401. Many other chips, including the 5700X, 5800X3D and several 4000 series parts, need 2423. The 5500X3D, 5600X3D, 5700X3D, 5800XT and 5900XT need 2803 or later. Check ASUS's CPU support page for your exact chip.

ASUS's documents give no separate power ceiling beyond the 105 W entries. The manual recommends at least a 350 W ATX 12V 2.0 power supply for a fully configured system and a larger one with power-hungry parts. A 105 W CPU with a discrete graphics card is a good reason to go higher.

Buying tips

  • Check the exact CPU model against ASUS's CPU support list and its minimum BIOS before buying.
  • Stay at or below 105 W.
  • If your BIOS is old, borrow or keep your current CPU installed to flash the BIOS first.
  • Make sure your cooler fits the AM4 socket.
  • Check that your power supply has enough headroom for the new CPU and graphics card.

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How to upgrade

Before you start

  • Back up important files before you open the PC.
  • Find your current BIOS version, then compare it with the minimum BIOS for any new CPU.
  • Download the BIOS from ASUS's support page. The flash file must be named PB550PS.CAP.
  • If you use BitLocker, back up your recovery key and suspend BitLocker before a BIOS update.
  • Keep the owner's manual at hand for exact slot and header locations.
  • Check that your case has room for any 22110 SSD and for the CPU cooler.

Steps

  1. Update the BIOS first (CPU upgrades)
    If you are fitting a newer CPU, flash the BIOS before swapping the processor, ideally with the old CPU still installed. Follow the BIOS update instructions in the manual.
  2. Back up and power off
    Back up your data, shut the PC down fully, switch off the power supply and unplug the power cable.
  3. Ground yourself
    Touch bare metal on the case or use an anti-static wrist strap before handling parts. Hold components by their edges.
  4. Open the case
    Remove the side panel. Refer to your case manual for how to open it.
  5. Install the part
    RAM: line up the notch and press the module firmly into the slot until it is seated. With two modules, use matched ones. SSD: fit it into M.2_1 or M.2_2 as described in the manual. CPU: the processor fits in only one orientation, so do not force it, and handle the delicate socket pins with care. Follow the manual's CPU and heatsink steps.
  6. Close up and reconnect
    Refit the side panel, reconnect the cables and power on.
  7. Check the BIOS
    Enter the BIOS and confirm it shows the new RAM capacity, SSD or CPU. If you use XMP memory, enable it there and check that the system is stable.

Good to know

  • ASUS's original manual lists memory speeds up to 4400 MT/s (O.C.) and mentions only 3rd Gen Ryzen. The newer spec page lists up to 4600 MT/s (O.C.) and more CPU families.
  • ASUS's documents differ on ECC. Treat it as working only on CPUs that support it.
  • ASUS doesn't confirm PCIe 4.0 for Ryzen G-series APUs. Assume PCIe 3.0 with those chips.
  • Some entries in ASUS's memory compatibility list look like errors, so verify the exact kit you plan to buy.
  • Ryzen 2000 chips are not on the official CPU list, even though a BIOS note mentions them.
  • If your board came in a prebuilt PC, check that maker's own limits on power and cooling.

Frequently asked questions

How much RAM can the ASUS PRIME B550-PLUS take?

Up to 128 GB across its four DDR4 DIMM slots. ASUS doesn't state a per-module size, but 128 GB over four slots implies 32 GB per DIMM.

Does the PRIME B550-PLUS support DDR4-3600 or faster memory?

Only 3200 MT/s and below run as standard. Faster kits rely on XMP or overclocking and aren't guaranteed. ASUS lists speeds up to 4600 MT/s (O.C.) on its newer spec page, while the original manual stops at 4400.

Does it have PCIe 4.0 M.2 slots?

One of them. M.2_1 is PCIe 4.0 x4 with 3rd Gen and 5000 series Ryzen. M.2_2 is PCIe 3.0 x4. APUs are likely limited to PCIe 3.0.

Why are SATA ports 5 and 6 not working?

They are disabled when an SSD is installed in the M.2_2 slot. You then have four usable SATA ports.

Which CPUs does the PRIME B550-PLUS support?

Ryzen 3000, 4000 G-series and PRO, and 5000 series, up to 105 W. Ryzen 2000 isn't on the official list. Many chips need a BIOS update first.

Do I need a BIOS update for a Ryzen 5000 CPU?

Often yes. Parts like the 5600X, 5800X and 5900X need BIOS 1004 and others need 1401, 2423 or 2803. The 5700X3D, 5600X3D, 5800XT and 5900XT need 2803 or later.

Official documents and references

This guide was written with AI assistance from the compatibility data PartsPrices verified against the manufacturer's documents. Always check your exact model and the owner's manual before buying or opening your computer.