Can I use my old CPU in either board?

Only if it matches the socket. The Z390 UD takes LGA 1151 8th and 9th gen chips; the Z790 ELITE AX takes LGA 1700 12th, 13th and 14th gen chips. The two sockets are not compatible.

Which is better for gaming?

The Z790 ELITE AX, because it supports newer CPUs, DDR5 and PCIe 5.0. The Z390 UD is fine for older games on an 8th or 9th gen chip but caps your frame rates through the CPU.

Is the Z790 ELITE AX worth the extra money?

If you are building new, yes: it is the only one of the two that takes current CPUs. If you already own an LGA 1151 chip, the Z390 UD saves you the cost of a CPU and DDR5 memory.

Does either board support ECC memory?

Both list ECC support, but that usually means unregistered ECC modules run without error correction on consumer chips. Do not buy either expecting full server-style ECC.

How much RAM can each take?

The Z390 UD takes up to 64 GB of DDR4 across four slots. The Z790 ELITE AX takes up to 128 GB of DDR5 across four slots.

Do I need a separate Wi-Fi card?

With the Z390 UD, yes, unless you use Ethernet. The Z790 ELITE AX has Wi-Fi 6E and Bluetooth built in.

Gigabyte Z390 UD Motherboard vs Gigabyte AORUS Z790 Elite AX

These are two different generations, not two versions of the same board. The Z390 UD is an LGA 1151 board for 8th and 9th gen Intel Core chips; the AORUS Z790 ELITE AX is an LGA 1700 board for 12th, 13th and 14th gen chips, so the CPU you own or plan to buy decides this. On price, the Z790 ELITE AX has ranged from $65.00 on 2026-11-03 to $189.99 on 2026-11-02, which is a wide swing worth watching before you buy.

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