MSI MAG B550 TOMAHAWK Upgrade Guide: RAM, SSD and CPU

Lifecycle and support

A current model: sold new and supported.

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

Memory (RAM) upgrades

The board has four full-size DDR4 DIMM slots (DIMMA1, DIMMA2, DIMMB1, DIMMB2) running in dual channel, for up to 128 GB in total. MSI doesn't state a maximum size per module. Four slots and 128 GB suggests 32 GB per DIMM, but that is our inference, not a confirmed figure. There is no soldered memory, so all RAM lives in the slots.

Only non-ECC unbuffered DIMMs are supported. ECC unbuffered modules will work, but only in non-ECC mode, and registered memory is not supported. Fill DIMMA2 first and use matched modules (same type, number and density) for stable dual-channel operation.

Speed depends on how you fill the slots. MSI lists JEDEC speeds from 1866 up to 3200 MT/s, and a top figure of 4866+ through A-XMP overclock mode, which is not guaranteed. That top speed applies to one single-rank DIMM per channel. One dual-rank DIMM per channel tops out at 3866, two single-rank DIMMs per channel at 4000, and four dual-rank DIMMs at 3600. Some modules run slower than their label unless you set the frequency in the BIOS. MSI also suggests keeping DIMM voltage below 1.35 V to protect the CPU, and recommends better memory cooling if you fill all four slots or overclock. Usable memory will be slightly less than what you install.

Buying tips

• Buy a matched kit rather than mixing modules.
• Two modules in the A2 and B2 slots give the best chance of reaching high speeds; four dual-rank modules will run slower.
• Choose standard non-ECC desktop DDR4 DIMMs, not laptop SO-DIMMs or registered server modules.
• Check the kit's rated voltage against MSI's below-1.35 V advice.

Storage upgrades (M.2 and SATA)

There are two M.2 Key M slots. M2_1 is connected to the CPU, takes 2242, 2260, 2280 and 22110 drives, and supports both NVMe and SATA M.2 SSDs. Its speed is PCIe 4.0 x4 or 3.0 x4 depending on the installed CPU, so a PCIe 4.0 SSD only gets full speed here with a CPU that supports it. M2_2 is connected to the chipset, takes 2242, 2260 and 2280 NVMe drives only (no 22110), and is PCIe 3.0 x4 at best. No SATA M.2 support is listed for M2_2.

M2_2 shares lanes with the PCIe slots. Using it together with PCI_E2/PCI_E3 drops it to x2 and disables PCI_E3. MSI's combination table is hard to read in the copy we have, so check the table in the owner's manual before filling both M.2 slots and the PCIe slots. It isn't clear whether running M2_1 in SATA mode disables any SATA port.

The six SATA 6Gb/s ports take 2.5-inch and 3.5-inch SSDs or hard drives. The board has no drive bays, so you need SATA cables and free bays in your case, and bay count and drive thickness limits depend on the case. RAID 0, 1 and 10 are supported on SATA, and RAID 0 and 1 on M.2 NVMe. MSI doesn't give a maximum capacity; it is limited by the drive and the interface.

Buying tips

• For the fastest drive, use M2_1 and pair it with a CPU that supports PCIe 4.0.
• Use M2_2 for a PCIe 3.0 NVMe drive; don't buy a 22110 or SATA M.2 drive for it.
• Check your case has a free bay before buying a 2.5-inch or 3.5-inch SATA drive.
• Buy a SATA cable if none came with the board or your old drive.

CPU upgrades

The CPU is socketed in a single AMD Socket AM4, with the AMD B550 chipset. MSI lists Ryzen 3000 and Ryzen 5000 processors, with a maximum of 105 W. Listed models include the Ryzen 3000 series, the 4600G and 4100, and 5000 series chips such as the 5600X, 5800X, 5900X, 5950X, 5800X3D and 5700X3D, plus the 5600G and 5700G APUs. Ryzen 1000 and 2000 and older 3000G-series APUs are not listed.

Every listed CPU needs a minimum BIOS: vA0 for Ryzen 3000, and vA4 up to vAF for Ryzen 5000 depending on the model (the 5700X3D needs the newest of these). We couldn't retrieve MSI's full support list, so these per-model versions come from a third-party copy of it that warns it isn't a complete list. One entry, the 5900X at vA7, looks odd next to the 5950X and 5800X at vA4, so check MSI's own CPU support list before buying.

MSI gives no separate power supply or cooler limit. Size your PSU and cooler for a 105 W-class CPU, and fit the heatsink with thermal paste so it seats tightly, since overheating can damage the CPU and board. The board has both CPU_PWR1 and ATX_PWR1 power connectors. Changing the processor can also reset BIOS settings to defaults.

Buying tips

• Check the exact CPU model against MSI's support list and note its minimum BIOS version.
• Update the BIOS before you install a Ryzen 5000 chip.
• Make sure you have a cooler and thermal paste ready; the CPU may not come with a cooler.
• Skip Ryzen 1000/2000 and older 3000G APUs; they are not listed for this board.

How to upgrade

Before you start

• Back up anything important on your drives.
• Look up your current BIOS version and compare it with the minimum for your new CPU. Update first if needed.
• Have the owner's manual open for the slot positions and the M.2 and PCIe sharing table.
• Have a Phillips screwdriver, thermal paste for a CPU change, and SATA cables for any new SATA drive.
• Work on a clean, static-free surface.

Steps

1. Update the BIOS if you are changing the CPU
   Download the latest BIOS from MSI's support page first. The Flash BIOS button on the rear I/O works without a CPU or memory installed: rename the BIOS file to MSI.ROM on a USB drive, connect power to CPU_PWR1 and ATX_PWR1, plug the drive into the Flash BIOS port and press the button. The LED flashes during the update and turns off when done. M-FLASH (Ctrl+F5 at POST, or from the BIOS) and MSI Dragon Center also work.
2. Back up and power down
   Back up your data, shut the PC down fully, switch off the power supply and unplug the power cable.
3. Ground yourself and open the case
   Touch bare metal on the case or use an anti-static strap, then remove the side panel. Refer to the owner's manual for exact disassembly of your case.
4. Install the new part
   For RAM, fill DIMMA2 first and use matched modules. For an M.2 SSD, choose M2_1 or M2_2 according to the limits above. For SATA drives, connect a SATA cable and power lead. For a CPU, remove the cooler, align the yellow-triangle Pin 1 marker on the AM4 CPU with the socket, then refit the heatsink with thermal paste and a tight seal.
5. Close up and reconnect
   Check that cables are clear of fans, refit the side panel, then plug in the power and switch on.
6. Check the BIOS sees the part
   Enter the BIOS at startup and confirm the new CPU, memory amount or drive is detected. Set the memory frequency manually if modules run below their rated speed, and recheck any settings that reset after a CPU change.

Good to know

• MSI doesn't state a maximum size per memory module.
• MSI's 4866+ MT/s figure is an overclock, not guaranteed. Different pages list slightly different extra overclock speeds, and the manual is the best guide.
• We couldn't retrieve MSI's full CPU support list. The per-CPU BIOS versions here come from a third-party copy, so confirm them on MSI's support page.
• The M2_2 and PCIe slot sharing table is hard to read in the copy we have, so check your manual. It isn't confirmed whether using M2_1 in SATA mode disables a SATA port.
• MSI doesn't guarantee against damage from operating beyond specification, including overclocking.

Frequently asked questions

How much RAM can the MSI MAG B550 TOMAHAWK take?

Up to 128 GB across four DDR4 DIMM slots. MSI doesn't state a per-module maximum; 32 GB per slot would match the total, but that isn't confirmed. Usable memory will be slightly less than what is installed.

What is the fastest RAM it supports?

MSI lists 4866+ MT/s through A-XMP overclock mode, which is not guaranteed and applies to one single-rank DIMM per channel. With four dual-rank DIMMs the limit is 3600. JEDEC speeds run from 1866 to 3200.

Does it support PCIe 4.0 SSDs?

Yes, in the M2_1 slot, but only when the installed CPU supports PCIe 4.0; otherwise it runs at PCIe 3.0 x4. M2_2 is PCIe 3.0 only.

Can I use a SATA M.2 SSD?

M2_1 supports SATA M.2 SSDs. No SATA support is listed for M2_2, which is NVMe only.

Does it support Ryzen 5000 CPUs?

Yes, including models up to 105 W such as the 5800X3D, 5900X and 5950X. They need BIOS vA4 or newer (up to vAF depending on the model), so update before swapping the CPU. Ryzen 1000 and 2000 are not listed.

Does it support ECC memory?

Only non-ECC unbuffered DIMMs are supported. ECC unbuffered modules work but run in non-ECC mode, and registered memory is not supported.

Official documents and references

• PDF MSI MAG B550 TOMAHAWK owner's manual (PDF)
  Slot layout, memory rules, M.2 sharing table and BIOS flashing
• PDF MSI MAG B550 TOMAHAWK datasheet (PDF)
  Official specification summary
• MSI MAG B550 TOMAHAWK specification page
  Memory, M.2 and SATA specs from the manufacturer
• MSI MAG B550 TOMAHAWK support page
  BIOS downloads and the CPU support list
• Pangoly compatible CPU list
  Listed CPUs with TDP and minimum BIOS (not a complete list)