Hi there, Lucas here from the Netherlands,

I have to say, I dont know much about computers yet but I just build my first pc:

AMD Ryzen 5 2400g, Gigabyte b450m ds3h, and no graphics card.

Then trying to boot up Linux Mint 19.1 cinammon on a USB drive. But it kept saying, ´´unable to write to IOMMU perf counter.´´ I hope anyone could help me. Curently I am running Linux Mint 18.3 on it but it says, ´´running in software rendering mode.`` So both version of Linux seem to have a problem. Please help!

You have video support in the CPU chip. Here is a quote from Gigabyte.com on the system board.

Have you installed a proprietary driver for video from AMD? If not, this message is from the default non-proprietary driver, and is just a warning. The chip set is capable of better performance with an AMD driver.
I suspect Mint would have a better driver choice in their repos. I don't run Mint, so I can't help any further. There are lots of Mint users here, so I'm sure someone will help.

Try googling for the IOMMU error. I saw some hits with a search like 'linux IOMMU error'.

duplicate of https://www.linuxquestions.org/quest...ms-4175653690/
this is frowned upon.