Yes, you can still use two graphics cards even if your motherboard doesn't have Nvidia SLI or AMD Crossfire. However, they can only be used for dual monitors. Without SLI or Crossfire, games won’t be able to make use of dual GPUs. Also, you can't use two or more GPUs to make a single output. Still, you can use each GPU on its own to run multiple monitors. In this way, it’s possible to use dual GPUs without the need for SLI or Crossfire.