On using a AMD Ryzen 5 3400G with an ASRock Rack X470D4U

Don’t do it.

Just don’t.

The third PCIe slot won’t work.

The plan in my PC Build was to have an x16 slot for the H700 RAID card, the x4 for the Asus 10Gigabit network adaptor, and a PCIe to U2 SSD card (plus U2 SSD) to act as the cache within a VM.

The issue is that the 3400G only supports 2 PCIe lanes, 1x x16 and 1x x4. According to the manual, you can split the x16 into 2x 8x’s but the option just isn’t there in my BIOS. I’ve tried updating and downgrading the BIOS, logging a case with ASRock (no response as of yet) so I’m forced to conclude that it does not work. This was echoed by a user in the Reddit Homelab discord who had the same issue with the same motherboard/CPU combo. He fixed it by upgrading to a Ryzen 7 3700X, however, this isn’t an option for me as the 3400G uses onboard graphics and other processors of a higher spec do not. EDIT DEC 2021: So the board has a basic GPU onboard meaning that processors without an iGPU will work in this board and you will have a video output. I wasn’t aware this was a feature on motherboards to have an onboard GPU, so I’ve learned something there. I’m now running a Ryzen 7 3700X.

Partially my fault for not checking, but honestly, it’s something I thought I wouldn’t really need to worry about.


  1. Late reaction, sorry
    I have the same cpu and motherboard combo.
    You dont need a cpu with an igpu because there is a simple gpu built in to the motherboard.
    It sucks that its not possible to use the third slot with a apu, but overall the board serves me quite well.
    Maybe i’ll upgrade to a better cpu in the future, mostly to be able to use all the slots.

    • Hi Michael, I have since upgraded to a Ryzen 7 3700X and found that there was an onboard GPU. I could now use all the PCIe lanes but I no longer have any use for them all due to a change of use in the board. I’ll go back and correct the post now.

Leave a Reply

Your email address will not be published. Required fields are marked *