Hello there, I have recently purchased a Radeon R9 290X, which I am now using as my primary card in a PCI express 3.0 16x. My previous card is a Radeon R9 290, and I plan to crossfireX these two cards. Unfortunately, I wasn't aware that I only have one PCI express 3.0 16x slot on my motherboard. The other PCI express is a 2.0 16x (equivalent to a 3.0 4x). I am wondering whether this will hinder the performance of the second card, and if so, should I buy a motherboard with two PCI express 3.0 16x slots? I have tried to search for information about this topic, but I can't find any definitive information. Any help would be greatly appreciated ! Thank you!
it is not worth it in my opinion. There will be a performance boost from 2.0->3.0 but you might not even notice it... Save your money for future upgrades!
The PCIe slot is probably physically PCIe2 x16, but possibly electrically PCIe2 x4. Intel Chipsets have a PCIe2 x4 link off the southbridge that gets used a lot for an extra PCIe x16 slot on a LOT of mobos. What chipset or Motherboard are you running ?
Thanks for your help! I think you are right, my motherboard is GIGABYTE GA-H87M-D3H LGA1150 It says: Slots: 1x PCI-Express 3.0 x16 Slot, 1x PCI-Express 2.0 x16 Slot (runs at x4), 2x PCI Slots Multi-Graphics: Supports AMD CrossFireX Technology I assumed that meant PCI-Ex 3.0 4x but I guess it means 2.0 4x? Thanks again for your help!
Yeah, thats a PCIe2 x4 electrical / x16 physical slot. Its running at PCIe2 x4 or equivalent of PCIe3 x2. Its not really fast enough for a graphics card, and not really for high end cards at all. And, on top of it all, it has to "speak" to the other GPU through the chipset, and the CPU!!! Lots of bad latency... If you want the crossfire to be any worth it, you will most likely to have to change motherboard. Its a pretty sweet setup already
Thank you so much again for your assistance! Do you figure this motherboard will do the trick: MSI Z97 U3 Plus ? Expansion Slots PCI Express 3.0 x16 2 PCI Express x1 2 PCI Slots 3 I figure I may as well involve the second card, for future-proofing, and this board has 2 3.0 x16 slots (the cheapest I could seem to find). If you know of any other boards that are cheaper please let me know. Thanks again
http://www.msi.com/product/mb/Z97_U3_PLUS.html#hero-specification Code: Slots • 1 x PCIe 3.0 x16 slot (PCI_E2, supports x16) • 1 x PCIe 2.0 x16 slot (PCI_E4, supports x4)* • 2 x PCIe 2.0 x1 slots* • 3 x PCI slots * The PCIe 2.0 x1 slots will be unavailable when the PCI_E4 slot has been installed. Looks like this board also uses 4 PCIE 2.0 lanes form the chipset for the second PCIE 16x slot so no go. Crossfire will work but the second card will be bandwidth starved as 4x PCIE 2.0 is similar to 2x PCIE 3.0. Search another Z97 board with two or three PCIE 16x slots that explicitly mentions in the specs that when the second slot is used, both the first and the second slots become 8x PCIE 3.0 (or 8x/4x/4x 3.0 with all 3 slots filled if it supports 3 way Crossfire).
Thanks dude! So this would be up to the task: ASRock FATAL1TY Z97X KILLER Slots: 3x PCI-Express 3.0 x16 Slots (run at x16 or x8/x8 or x8/x4/x4), 3x PCI-Express 2.0 x1 Slots Multi-Graphics: Supports AMD Quad CrossFireX, 3-Way CrossFireX, CrossFireX and NVIDIA Quad SLI, SLI Technology
I've got the exact same thing. My board is 16x/4x @ PCI-E 2.0 for Crossfire. While it's not ideal, for my 7850s it IS a huge improvement over a single card. Unless you're trying to run 4K, and with how powerful those cards are already, the performance cut of using a 4x slot vs buying a new board isn't gonna be noticeable outside of benchmarking, IMO. Just had a thought, since the R9 series uses the PCI-E bus for Crossfire talk instead of the card-to-card bridge, would that make a bigger impact on a 4x slot? I'm not as up to date on that aspect of all this.
I think AMD recommends PCIE 3.0 for bridgeless Crossfire on R9 290(X). I ran for a while the fist card in the top 8x slot and the second card in the bottom 4x slot instead of the usual 8x top, 8x middle and there was a small penalty, can't remember exactly, around 10% I think. Mostly noticeable in 3DMark but also to a smaller extent in BF4.