AX850 causing problems to Sapphire HD 4890

Hi;

I recently received my new AX850 to replace a similar PSU but less effcient

When I connect the GPU with single PCI-E cable-pair, using the 2 x six pins, and power on; the GPU fans spins to max with blank screen, sometimes the system boots normally to windows (although the screen is blank, but I know from my Logitech G15 keyboard LCD and the Win7 start sound). I tried the other PSU PCI-E cable and another 8-pin socket, I also tried two DisplayPort cables and two DVI cables with no success.

When I use TWO PSU PCI-E cable-pairs together, using Six pin from first one and the Six-pin of the second, there is an improvement in that the above doesn't happen always but still happen.

Is the PSU faulty? Or am I doing something wrong.

This setup is the same when using my old PSU and worked fine.

Any help would be appreciated.

More info.

I've carried more expermentation and found out that:

1) Using single PCIe cable-pair, the GPU issue always happens and cannot use PC.

2) Using Two PCIe cable-pairs, the GPU issue happens only after cold start (ie if the PSU was turned off from Mains socket for a while). When cold start there is a delay between pressing the PC power and the PC starting. When PC starts, the GPU issue happens.

Can the AX850 drive Sapphire HD4890 with single PCIe cable-pair?

RAM GUY thanks for the reply.

I think RMA is the solution, I think single PCIe cable-pair should do.

I'll RMA to the supplier as this might be quicker.