Newer CPU PCIe and DMI confusion

[Luckywales]

Hi everyone - let me begin by saying I've seen posts that are similar to this but don't appear to address my direct concern.

I currently have an i7-6850k on an X99 board, and am about to upgrade. I purchased this to take advantage of (almost all) the available PCIe lanes from the CPU...not CPU + chipset...just the CPU, which had 40 lanes. Included in my setup are two M2 NVME PCIe drives that I think are taking full advantage of this setup on my motherboard (960 pros).

Has something fundamental changed over the last 3 years? I'm asking because when I look at the latest i7-9700k, it has less lanes. Whilst I understand that the CPU, plus the chipset lanes (on say a Z390) sum to 40 or more, aren't the lanes which are additional to the CPU just sharing the same Direct Media Interface (DMI) bandwidth? Or is something else happening in the background? Does this cause a bottleneck to the 970 pro speeds that I think I'll purchase for the M2 slots?

I'm not sure I'm asking the right question here, but with multiple GPUs, LAN and wifi cards will I be able to dedicate the entire bandwidth to my two M2 drives (not worried about the board shutting off SATA ports)?

I've looked at 4 YouTube videos on the basics of PCIe lanes vis-a-vis CPU and chipset, but I can't find an answer to the fundamental issue that the chipset might ultimately be dividing up the available bandwidth made available by the CPU. So did we go backwards in reducing the number of CPU lanes?? That can't be right? Right?

 

[gasaraki]

OK, first the issue is that you are comparing a HEDT chipset vs. a mainstream chipset.

The X99 was a High End DeskTop chipset which provided 40-lanes. The i9-9900K and lower all run on the Z390 chipset that is considered mainstream line that only provides 24-lanes. To get your 40-lanes, you'll need to get the X299 chipset, which the the direct replacement of your X99 chipset. All the new X299 cpus from this year provide 40-lanes. Don't get the "low end" X299 CPUs from last year that provided less.

Or you can get an AMD X399 chipset and get a threadripper cpu and get 60-lanes.

Now to answer you question. Yes. Everything not the video cards and M.2. drives with be PLXed behind the DMI connection that is 4x dedicated lanes. However some motherboards (ASUS) in the Z390 line have been able to put two M.2 PCI slots and run RAID 0 and get 7GB/sec+ bandwidth from the CPU.

 

[Luckywales]

OK, first the issue is that you are comparing a HEDT chipset vs. a mainstream chipset.

The X99 was a High End DeskTop chipset which provided 40-lanes. The i9-9900K and lower all run on the Z390 chipset that is considered mainstream line that only provides 24-lanes. To get your 40-lanes, you'll need to get the X299 chipset, which the the direct replacement of your X99 chipset. All the new X299 cpus from this year provide 40-lanes. Don't get the "low end" X299 CPUs from last year that provided less.

Or you can get an AMD X399 chipset and get a threadripper cpu and get 60-lanes.

Now to answer you question. Yes. Everything not the video cards and M.2. drives with be PLXed behind the DMI connection that is 4x dedicated lanes. However some motherboards (ASUS) in the Z390 line have been able to put two M.2 PCI slots and run RAID 0 and get 7GB/sec+ bandwidth from the CPU.

Thank you very much for clarifying - that makes much more sense. Looking at the price difference, it looks like Intel has got BS crazy. The difference between the 6700k and the 6850k was not that bad, which is why I went that direction.

I'm a little confused about your response to the use of the DMI. First, doesn't everything eventually "flow" between the CPU and chipset component? If so, regardless of whether it's a dedicated lane from the CPU, or a motherboard lane...they all have to fit on the DMI bandwidth right?

I don't understand what this means, sorry: "Everything not the video cards and M.2. drives with be PLXed behind the DMI connection that is 4x dedicated lanes."