Hi Matthew,
It sounds as if your card is insufficiently powered. You would need to use 2, 2x4-Pin Molex -> PCIe adapters. So, you'd have 4 molex connectors being turned into 2 PCIe connectors. Using just a straight 1x4-Pin Molex -> PCIe won't do the job usually... even if they came included with the card.

This is an uncommon limitation in power distribution for your motherboard. A molex cable would likely solve your issue, send me an e-mail and I can arrange setting you up with a replacement.

Have you tried all 4 cards simultaneously in x16 slots (on board) not using an extender? How much power do you have and what cards are you using? What CPU/RAM/Peripherals?

Doesn't an 890FXA-GD70 have 4 usable x16 double slots? I glanced at the photo at MSI to refresh my memory and it seems like it does unless the board is snug up against the side of a case in which case you couldn't fit that fourth in there, hence using the x16 extender I guess huh?

What PSU and what CPU are you using? I understand you believe power is not a concern but if your rails on not properly balanced you could be overloading one of them. PSU & CPU model?

Of course it would be ideal if you could slot that fourth card on board w/o an extender to test.

Well with that PSU I concur that it is most likely not a PSU concern. I will assume your PCIe 6/8-pin power is marked per rail and you are connecting each 5830 to a single rail. Even if you shared a rail between two cards it probably wouldn't matter much since the alternate rail would fill in the slack.

Did you get an x16 extender with a molex power connector to supply PCIe slot power via a molex peripheral or just a standard x16 extender no molex? I didn't understand what you meant about the "molex splitter".

Something to keep in mind though when using these PSUs with multiple rails is how the rails are wired. I had to get wiring schematics from Seasonic to make sure I was balancing my loads on a dual rail PSU. The molex peripherals, CPU 12V, ATX and misc are on one rail as well as a couple PCIe 6/8-pin power cables and the other rail ran a couple more PCIe 6/8-pins.

It sounds as though you are safe on rail load balancing though. I would hope that Silverston put CPU/ATX/Peripherals all on a rail (or two) alone.

I would probably lean toward a defective extender.

Some new products being added Tuesday:

* PCI -> PCIe Adapters (Which will run your card even through an extender, at full speed, from a traditional PCI slot)
* Kill-o-Watt meters

We've also recently added:

* DVI Connector GPU Dummy Plugs (Direct DVI connector)
* VGA Connector GPU Dummy Plugs
* DVI -> VGA Adapters
* Molex -> PCIe 6pin PSU adapters
* Chassis stacking kits

Pictures are on the way as well!

I want to modify one of my pci-e x1 cables so to give it power from the psu..
I see that there are 4 pins giving 12v .
http://en.wikipedia.org/wiki/PCI_Express#Pinout
(A2,A3,B1,B2).
But I sow that someone re-routed 5 pins instead of 4 pins...
http://blog.zorinaq.com/?e=44

Can you help me and tell me how many pins do I need to re-route?
Thank you.

There's a notice at the top of the page:

"Notice: Bitcoin payment temporarily disabled until exchange issues are resolved."

I order some cables over the weekend but there is no confirmation email and there is no reply to email. When would it be shipped out? Invoice ID: 243-1308461686
Thanks.