6700k vs 6800k PCi x16 SLI

mmedeiro

Honorable
Jan 4, 2013
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10,530
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Hi all

I'm looking to upgrade from a LGA 2011 4820k. I always run my GPU's in SLI, so PCi lanes are important. I'm a little confused regarding the PCi lanes on each chip set.

The x99 says its has up to 40 lanes but only with a compatible CPU but it seems like the 6800k is only a 24 lane chip and therefore ill be running 16x 8x?

I'm not finding any 2011-v3 with 2 16x PCI slots. Again 16x 8x.

Am i confused, neither CPU is capable of running 2 GPUs @ 16x?

Its been a while since i researched this. Is 8x the max speed ill need for a GPU?

My current system
x79 Sabertooth
i7 4820k
2x MSI 980ti GC in SLI
32 gb Ballistix sport 1600
Rosewill Lightning 1300w

Thanks

 

ryguybuddy

Estimable
Jul 3, 2016
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No, neither CPU can run both at 16X, although I see no reason why that would be a problem. The only GPU to saturates the PCIe 3.0 x8 interface is the Nvidia Titan X (pascal) at 4K, and I am assuming you don't have two of these.

If you really want both cards to run at 16x, get the 6850K instead. It is pretty much the 6800k but with a higher clockspeed and 40 PCIe lanes.
 

Ecky

Illustrious
Moderator
The performance difference between 8x and 16x is negligible. SLI must be symmetrical, so if you don't have the lanes for 16x/16x, it'll run 8x/8x.

-6700K has 20 lanes, and could run two cards in 8x/8x with 4 lanes leftover for whatever - an M.2 SSD?

-6800K has 28 lanes, and could run two cards in 8x/8x with 12 lanes leftover for whatever.

-6850K has a full 40 lanes and could run two cards in 16x/16x, but the performance difference is negligible.

That said, a single 1080 will probably be faster than 980 Ti SLI in most cases, draw 1/3 the power, and be cheaper. You might be better served by selling your two cards and moving up to a single 1080.
 

Ecky

Illustrious
Moderator
Looked at some benches, it's really back and forth. Probably not worth your time and effort, unless you feel like it'd be nice to have a system that draws <350w under load.









 
First let me say I wouldn't suggest upgrading unless your overclocking. The 6800K is a lower clock and not a great improvement. Here is the compare and im unsure why Intel release the CPU at such a low clock rate. Overclocked tho you should get beyond anything the old 4820K would do.
http://www.anandtech.com/bench/product/1330?vs=1727

Also a heads up the 200 series with kabylake will have 24 lanes. Here is a compare between the 6700k and 6800k.
http://www.anandtech.com/bench/product/1543?vs=1727
 

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