Any issues running SLI with one card at x16, one at x8 (PCIe 3)

[wunkley]

I'm going to build a new dedicated gaming rig from the ground up in 3 or so month's time. Main thing I'm umming and ahhhing over is to wait for Skylake, or go X99 hex core (I really like the idea of 6 physical cores over 4, as I think some games will start to benefit).

I'm posting this in the GPU section, as I have concerns about running 2 cards in SLI at differing PCIe speeds. Bear with me....

From my limited research, if I do go x99 I would most likely get a 5820k chip. This 'only' allows 28 PCIe 'lanes', so if you run 2 cards in SLI, one will be at x16 and the other at x8. This is as I understand it, is that right?

Now, I'm no expert, but I'm something of an obsessive about using SLI and experiencing and eliminating stutter and microstutter in certain games. I've used SLI for years, currently on 780Ti SLI. I want to go one TX probably to start with, but have itchings to try out 4k soon, so will end up needing 2 cards. It will happen

It may be daft, but I can just sense problems arising from running 2 cards in SLI at different PCIe speeds. So my questions are:

1. Does anyone run this 5820k x99 set up now with SLI and have any input?
2. Are there any motherboards that allow you to force x8 for both cards, rather than one at x16 and one at x8? From what I've read x8 with "PCIe 3" is more than good enough anyway.
3. Should I just fork out for a 5930k with the full 40 lanes so there are no issues and both cards will run at x16
4. Should I wait for and get Skylake instead?

Ta

 

[wunkley]

I run a 5930k with TitanX SLi @ PCIE 3.0x16

Can I limit one to PCIE 3.0x8 in the BIOS? or would I have to physically move it?

Just thought I could run a heaven 4.0 benchmark for comparison if it's easy. I'm not moving cards about though.

You tell me bud

It's not so much slightly reduced performance I'm concerned about. I have no doubt it would be negligible anyway. It's the dreaded SLI MICROSTUTTER issues I'm bothered about. I just want to do everything possible to eliminate any possible SLI stutter issues for my new build. And I have this (maybe irrational) idea that running 2 cards at different PCIe speeds (like they will in an X99 5820k setup) might cause stutter probs...

 

[wunkley]

I thought if you had say a card in a x16 slot and one in a x8 slot then it would run x8/x8 automatically ?

So did I. But from what I've read, on X99 and using a 5820k CPU it will run one card at x16 and one at x8. What I'm trying to find out is what I posted in my opening post, and if this might cause any issues with STUTTER.