First thing is to identify what motherboard is being used. The OP PMed me and said the addition of the 8th card causes variation of rate from 28 to 14 and back. Knowing the motherboard and bios revision would help.
Make sure to have virtual memory high enough. I would do at least 24576 for 6 card, some multiple of 4096 thereafter if using 8 like 8 x 4096.
The Power supply make be adequate, but if not cabled properly to the risers that can be an issue as well. Make sure no more than 2 cards per Molex or Sata chain. Splitting a 6 or pin cable is usually safer than using those two thinner cables.
Opening up task manager will usually help prove CPU is not pegged at 100% on a core or something is not stuck in the background. Using Afterburner helps show if the GPU core clocks are throttling and why they might be throttling.
Most important is to know the mobo model though.... else we're all just guessing.
Thank you. I double checked your suggestion "Make sure no more than 2 cards per Molex or Sata chain. Splitting a 6 or pin cable is usually safer than using those two thinner cables." and I found the possible cause. I am using dual PSU's. I had criss crossed two sata cables. So a GPU VGA cable was going to PSU1, while the riser was going to PSU2. This happened to two cards that were criss crossed.
I corrected it and am now testing it. I'm very thankful for everyones help and hope this may help someone else in the future. Will keep you guys posted.
