Okay, there's a terminology problem here.
When we say 6-pin or 8-pin, we mean the 6/8 pin
PCI-E power cables. EVGA G2 750w has four.
Basically, you could use a 8pin PCI-E splitter and connect it to both the RX GPU and direct to the riser's 6 pin socket.
Alternately, it's possible to get (or make) cables that convert the PSU's second CPU EPS12V 8pin connector into a pair of 6/8pin PCI-E and use them to power a pair of risers.
Example:
http://www.ebay.com/itm/CPU-8Pin-to-Graphics-Video-Card-Double-PCI-E-PCIe-Power-Supply-Splitter-Cable-/272720358725Or.... for the risers with the direct molex connection, you could obtain more EVGA G2 compatible molex cables, as for an EVGA G2 all the SATA/PERF sockets on the back of PSU are wired identical/interchangable. (EVGA G2, G1 and GS all use the same pinout for the molex cable)
O.M.G.
That. That is exactly what I was confused about. And it's sitting right under my nose.
So given I want to run 7 cards on one mobo, and I have 8 PCI-E (VGA) cables amongst 2 PSUs.
PSU 1Mobo + CPU
GPU1: VGA1 + Perif-1 to Molex string (1 of 4)
GPU2: VGA2 + Perif-1 to Molex string (2 of 4)
GPU3: VGA3 + VGA4 (to 6-pin riser)
PSU 2GPU4: VGA5 + Perif-2 to Molex string (1 of 4)
GPU5: VGA6 + Perif-2 to Molex string (2 of 4)
GPU6: VGA6 + CPU to 6/8 splitter (OR buy a 8pin to 8pin PCI splitter for both)
GPU7: VGA8 + CPU to 6/8 splitter (OR buy a 8pin to 8pin PCI splitter for both)
Is that right? That makes so much more sense now...!
Correct. My 750w G2 are setup similar to your PSU2 above, CPU to 2x 6pin splitter and using 1 molex string per riser.
(I had spare EVGA G2 molex cables, and on the PSU side PERIF/SATA sockets are wired the same)