It is very important if you care about performance. On inference, a lot of data has to go from one card to another. I was using 1x risers and it sucked. If you have two similar nvidia cards, you can get around by using nvlink bridge.
Otherwise you should aim at pcie 4 8x at least when looking for a Mainboard. I sniped a epyc system from ebay for 1000€ that has 6 pcie 4 16x and it rocks it all with 4 3090.
It is very important if you care about performance. On inference, a lot of data has to go from one card to another. I was using 1x risers and it sucked. If you have two similar nvidia cards, you can get around by using nvlink bridge.
Otherwise you should aim at pcie 4 8x at least when looking for a Mainboard. I sniped a epyc system from ebay for 1000€ that has 6 pcie 4 16x and it rocks it all with 4 3090.
https://preview.redd.it/u0bvy2kkzw1c1.jpeg?width=4032&format=pjpg&auto=webp&s=ecb164bbf59504e590c19403554e24df8f9236c8