1. CPU and motherboard: socket first, then chipset
The socket is the one check with no workaround. An AMD AM5 processor only drops into an AM5 motherboard; AM4 chips only fit AM4 boards; Intel's Core Ultra desktop chips use LGA1851 while 12th-, 13th- and 14th-gen Core use LGA1700. Sockets are not adaptable, and pin counts differ, so a mismatch means the CPU physically will not seat.
The subtler failure is a matching socket with a chipset or BIOS that does not know your CPU. This happens every time a new chip launches on an existing platform: the board is electrically fine but ships with firmware predating the processor, so it will not POST until the BIOS is updated. Look up your exact CPU model on the board maker's CPU-support list and note the minimum BIOS version. Many current boards can flash firmware from a USB stick with no CPU installed — worth confirming before you buy if you are pairing a brand-new chip with an older board.
2. RAM: generation is a hard rule, speed is a soft one
DDR4 and DDR5 use different pin counts and a different notch position, so they cannot be swapped and no board accepts both in the same slots. AM5 and LGA1851 are DDR5-only platforms; AM4 is DDR4-only. Get the generation right and the rest is tuning rather than compatibility.
After that, three softer checks: the kit's rated speed should appear on the board's supported list (its QVL) if you want the advertised speed via EXPO or XMP; the module count has to fit the available DIMM slots; and be aware that filling all four DDR5 slots usually forces a lower stable speed than running two modules. A kit that is not on the QVL normally still boots — just at the platform's default speed until you tune it.
3. Power supply: wattage, then connectors
Sizing a power supply is arithmetic: add the CPU's and GPU's rated draw, allow roughly another 100W for board, drives, memory and fans, then leave about 30% headroom. That headroom is not padding — modern graphics cards pull brief transient spikes well above their nominal rating, and a PSU sized exactly to the average will trip its protection under load.
Connectors are a separate check people skip. High-end cards use the 16-pin 12V-2x6 connector, the revised version of 12VHPWR introduced with the ATX 3.x specification; the fix improved the contact design so a partially seated plug cannot carry full current. Either your PSU has a native 12V-2x6 cable rated for the card's draw, or you use the adapter that came with the card. While you are there, count EPS 8-pin CPU connectors — some boards want two — and confirm you have enough PCIe 8-pin leads on separate rails.
4. Physical fit: GPU length, cooler height, form factor
Three measurements settle whether the build closes. First, GPU length: every case publishes a maximum graphics-card clearance in millimetres, and you compare the card's length against it — not its model name. Thickness matters too, since 3-slot and 4-slot coolers need that many free expansion slots, and a front-mounted radiator or a drive cage can cut the usable length below the headline figure.
Second, cooler height: air-cooler clearance is the most common physical failure in first builds. Compare the cooler's height in millimetres against the case spec, and check that its mounting kit covers your socket. For an all-in-one liquid cooler, the question becomes which radiator sizes the case supports and in which positions. Third, form factor: the case has to list your board's size — ATX, micro-ATX or Mini-ITX. A smaller board fits a larger case, never the reverse.
5. Storage and PCIe: slots share lanes
NVMe drives are where “compatible” gets quietly conditional. A board's M.2 slots are not equal: populating a particular slot can disable a pair of SATA ports, and a secondary M.2 slot may share lanes with the main PCIe x16 slot, dropping your graphics card from x16 to x8. Neither is a failure — the system boots fine — but it is a trade the manual documents and the spec sheet does not.
PCIe generations themselves are backwards and forwards compatible: a PCIe 5.0 card runs in a 4.0 slot at 4.0 speeds, and a Gen4 SSD works in a Gen3 slot. So generation is rarely a compatibility question — lane allocation is.
Check a whole parts list at once
Every check above is mechanical, which is why it is worth automating. Add your parts in the PlanMyPC system builder and each component is validated against the rest as you go — socket, RAM type, wattage headroom, and clearance — with any conflict explained in plain language. If you would rather see how the validation works before starting, the compatibility checker walks through it step by step, and how to plan a PC build covers choosing the parts in the first place.