Mystery Expansion Slot on Rampage IV Extreme (3rd ROCKET possible?)

[Rob Anderson]

For one of my machines, I've got 2 RED ROCKETS and 2 nVidia 690's installed already. I'd like to install a third ROCKET but the only slot that I still have open is #3. In the manual this slot is called:

PCIe 3.0 x8_2B

The slot directly above it with one working ROCKET card already installed is called PCIe 3.0 x8_2A. Any ideas if this "2B" slot will work? I've gone through the manual and everything indicates this slot is a 'normal' PCIe 3.0 x8 lane, but when I tried moving one of the existing cards down, REDCINE-X wouldn't see it.

[Jeff Kilgroe]

Dual 690's... Overkill much?

Anyway, the "2B" slot is a bridged or tandem slot that shares bandwidth with the "2A" slot.

The PCIe 2.0 X1 slot is always active.

Of the PCIe 3.0 slots, you have 40 lanes you can divide up amongst them, but this motherboard only allows those slots to exist as either X16 or X8. And the 2B slot can only be active if the 2A slot is active, and only if the 2A slot is set to X8 mode. Then it shares bandwidth with the 2A slot, if used. You should first look in your BIOS setup and see how you have your PCIe slots configured, make sure 2A is active as an X8 slot. I'm not sure how two Rockets would perform in a shared in a tandem slot arrangement like this, there is plenty of bandwidth for two of them, but I haven't tried it to get any real-world feel of how it works.

[Gary Paul Walker]

Dual 690's... Overkill much?

Jeff (and with all apologies to the OP for slightly diverting the question), I'm building a system and was going to throw in a 4gb 690 - how do you rate them though? obviously there are a lot cheaper.. (and I'm using a non-rocket system)

[Rob Anderson]

Dual 690's... Overkill much?

Anyway, the "2B" slot is a bridged or tandem slot that shares bandwidth with the "2A" slot.

The PCIe 2.0 X1 slot is always active.

Of the PCIe 3.0 slots, you have 40 lanes you can divide up amongst them, but this motherboard only allows those slots to exist as either X16 or X8. And the 2B slot can only be active if the 2A slot is active, and only if the 2A slot is set to X8 mode. Then it shares bandwidth with the 2A slot, if used. You should first look in your BIOS setup and see how you have your PCIe slots configured, make sure 2A is active as an X8 slot. I'm not sure how two Rockets would perform in a shared in a tandem slot arrangement like this, there is plenty of bandwidth for two of them, but I haven't tried it to get any real-world feel of how it works.

Great info. Thanks Jeff.

The dual 690's are being used for an Oculus Rift development project. This particular box is my second rendering workhorse. The prime is a server board, already running 3x Rockets. Wanted to get comparably expected performance out of this one, when the overflow is needed.

[Rob Anderson]

Jeff (and with all apologies to the OP for slightly diverting the question), I'm building a system and was going to throw in a 4gb 690 - how do you rate them though? obviously there are a lot cheaper.. (and I'm using a non-rocket system)

Save money and run with dual 680's in SLI. Same noise and heat, although a little more power drawn (390w), but practically the same performance for cheaper.