What is AM4?
AM4 (Socket AM4) is the CPU socket AMD used for its mainstream desktop processors across several generations of Ryzen CPUs and APUs, plus Athlon and some A-series chips. AM5 succeeded it. Because AM4 spanned so many CPU generations, you'll meet a lot of boards and processors built for it.
Key specs
| Feature | AM4 |
|---|---|
| Socket type | PGA (pin grid array): 1331 pins on the CPU, holes in the socket |
| Memory | DDR4 only |
| CPUs | Ryzen desktop CPUs and APUs from the 1000 to the 5000 series, Athlon, some A-series APUs |
| PCIe | PCIe 3.0, or PCIe 4.0 with supported CPUs and chipsets such as X570 and B550 |
| Chipsets | A320, B350, X370, B450, X470, A520, B550, X570 and others |
| Successor | AM5 (LGA 1718, DDR5) |
Installing an AM4 CPU
- Lift the socket's retention lever (a ZIF, or zero insertion force, socket).
- Line up the gold triangle on the CPU corner with the triangle on the socket and lower the CPU in. It should drop into place with no pressure.
- Lower the lever to lock it, apply thermal paste and mount the cooler.
The pins are on the CPU, so handle it by the edges and never press it in. Bent pins are the classic AM4 problem. When removing a cooler, twist it gently before lifting, because dried thermal paste can pull the CPU out of the locked socket and bend pins.
Compatibility gotchas
- BIOS support: older boards often need a BIOS update before they can run newer Ryzen chips, and some chipset and CPU combinations aren't supported at all. Some boards can flash the BIOS without a CPU installed.
- Memory: DDR4 only; DDR5 won't fit the slots.
- Not AM5: AM4 CPUs don't fit AM5 boards and AM5 CPUs don't fit AM4 boards, though many AM4 coolers can be mounted on AM5.
- Not Epyc or Threadripper: AMD's server and workstation CPUs use different, larger sockets.
- Video output: most AM4 Ryzen CPUs have no integrated graphics. The board's video ports only work with an APU (the G models); otherwise you need a graphics card.
For the CompTIA A+ exam
Core 1 (220-1201) objective 3.5 covers motherboard compatibility, including AMD and Intel CPU socket types. For AM4 vs. AM5, the easy shortcut is pins and memory: AM4 is PGA with pins on the CPU and uses DDR4; AM5 is LGA with pins in the socket and uses DDR5.