Quote from: grottenolm on April 11, 2013, 03:05:26 PM

Since you have this motherboard:

http://www.asrock.com/mb/Intel/Z77%20Extreme6/?cat=Specifications

You should have those slots:

- 2 x PCI Express 3.0 x16 slots (PCIE2/PCIE4: single at x16 (PCIE2) / x8 (PCIE4) or dual at x8/x8 mode)
- 1 x PCI Express 2.0 x16 slot (PCIE5: x4 mode)
- 1 x PCI Express 2.0 x1 slot

From my perspective (having done PCIe signal quality measurements etc. already) any kind of extender cable are potentially trouble for both signal quality and power supply. Not being detected at boot time sounds a bit more like the former. But fortunately for bitcoin mining you don't need much bandwidth. So here is my suggestion:

Check in BIOS Setup (or rather UEFI Firmware Setup here) if you can set the PCIe mode to the slowest Gen1 speed. This should at least give you the highest chance of success, with no impact at all on mining speeds.

Exactly my thoughts. PCIE is not meant to truly be extended externally. So when putting extender cables on the cards, you're potently adding noise. Signal integrity is very important at even PCIE 3.0 1x speeds.

As for you power usage, I would not take anyone word on how much of a power supply you really need. Buy a KILL-A-WATT meter, plus in one card, power up the system full load, check power consumption, and compare it to idle. Multiply difference by 3x, and add ~20%.

Also so keep in mind most switching power supplies ( Computer/PC type ) operate most efficiently at 25%, 50% or 75% load. So with that in mind, when adding 20% dont be afraid to add a little more if it means matching efficient load statistics. Also for what it is worth, most PSUs are the most efficient at 50% load, but always check OEM specs before making that judgment call. As some do vary.