Is it possible to mind bitcoin and other cryptocurrency by using a few old PCs? I have a couple PCs that I'm not using, and I figure I could make them into miners so I can mine some crypto, but would it work with older PCs? Both of the PC I have don't have the best specs, like 4gb ram, no graphics card, or anything. I assume they won't do much unless they each had a decent graphics card and maybe upgraded ram?