Back in 2014 I was cheap and instead of buying quality PSUs I would use these no name type of low quality PSUs which were like 450Watts max. I had tons of these because they generally were always included in a computer case and I never used them.

They only had 1 PCIe connector but you would easily make another PCIe connector if you rewired some of the other unused plugs. Keep in mind I used this to run an Antminer not power a GPU rig.

The issue was that the efficiency was crazy bad. It was like 65% or something. So if you are pulling 100 Watts from the wall, 35 Watts  is basically lost as heat and only 65 Watts went to power my Antminers.

They also usually only lasted 2 weeks and then would just die. I didn't even run them at 100% load, maybe 70% load and they just died shortly after. I think they are mostly for housewives who use their computer to browse facebook and pull less than 40 watts total from the PSU. But for mining... forget about it.