Are there any motherboards out there that support 2xPCIe 2.1x16, PCIe x 8 and PCIe x 1 all at the same time? I have seen a number of them with 4 (or more) PCIe slots, but they all seem to drop PCIe slot bandwidth if I put in more than two or three cards.
Ultimately, I would like to build a system with two high-end graphics cards (two x16), an Adaptec 5805 RAID controller (x8) and a SoundBlaster X-Fi Titanium sound card (x1), all of which are running at their full bandwidth simultaneously. Is this even possible?
I don't think such a thing is possible at the present time due to chipset limitations. As far as I know the most available PCI-E lanes come from the AMD 890FX, which allows for 42 lanes configured as two x16(may be split to x8+x8),one x4, and six x1 lanes, intels X58 only allows for 36 lanes total iirc.
I'm pretty sure those boards will switch to x8 mode if you populate more than two of the slots. However I believe they ran some benchmarks and found that going from x8 to x16 has a fairly small impact with currently available cards.
Trashy may be right. It is hard to find definite information on what individual slots do when more that 2 of the slots are used. One (I think the MSI board, but could be wrong) added words to effect that is a 3rd GPU was installed that slots 1 and 3 would revert to x8 mode. Does that mean the have 2 x16 GPUs in slots 1 and 2 would be affected by adding a x8 RAID controller in slot 3 or a 1x sound card in slot 4? Got me.
I agree that going from x16 to x8 in the sort of beast Trashy is describing would have minimal impacts on overall performance. When you build it, lets us know how it performs.
That's been my frustration since I built my most recent system last year--manufacturers are vague (or completely silent) on exactly what happens when you use PCIe slots in combinations other than what they think you need. But if you're building a high-end gaming rig, who uses the built-in sound system? And why use the chipset RAID when you can get much better RAID performance with a dual-processor add-in card with a battery-backed cache? (And yes, I would want RAID even with solid state drives for the fault tolerance--drives always fail, even SSDs.)
Thanks for all your input. You've confirmed what I suspected--that I'm dreaming too big.