I don't know much about power supplies, but I know enough to know that I've never seen this....
From what I've caught onto over the years is that most power supplies connect to the mobo 2 ways, 1 through a 24 pin connection, and another (near the cpu) 4 pin connector. The mobo I'm looking at appears to have a that 24 pin connection, but near the cpu it looks like an 8 pin connection????
the 8pin is still your cpu plug, what you recognise as the older 4pin but most modern cpu's require more power so it changed to 8pin a while back, I have an 8pin socket but only have a 4pin plug, you can just use 4 pins no problem, it should fit into the lowermost 4 pins of the socket, not the middle, but the plug should be formfit so will only go into the right place however if you're aiming for big overclocks, get a 8pin psu to help supply the juice
and the 20+4pin is same as ever although no boards I've seen use just 20 pins anymore
hope this helps,