NVMe on PCIe 4x slot provided by DMI 2.0 - Anyone tried this?

Unknown-One

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Has anyone tried slapping a modern NVMe SSD into a PCIe 4x slot that's provided by the chipset via DMI 2.0?

In theory, a good SSD is enough to totally saturate DMI 2.0 all on its own, and there are other devices sharing that bandwidth. I'm curious if the chipset will prioritize certain devices over others in order to prevent heavy load on the SSD from causing the integrated ethernet, sound, USB, and SATA from bogging down.
 

alienb

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It's a bit slower in benchmarks on my X299 board, but works fine. No noticeable difference in performance. (Samsung 970 Pro 1tbs)
 

oleNBR

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Has anyone tried slapping a modern NVMe SSD into a PCIe 4x slot that's provided by the chipset via DMI 2.0?

In theory, a good SSD is enough to totally saturate DMI 2.0 all on its own, and there are other devices sharing that bandwidth. I'm curious if the chipset will prioritize certain devices over others in order to prevent heavy load on the SSD from causing the integrated ethernet, sound, USB, and SATA from bogging down.
pcper and tweaktown both did review for SSD on HEDT boards vs on z170 -z370 boards turns out consumer board is much more optimized, either because of chipset or purely because of CPU. tweaktown also did test of different window OS difference, server OS give best performance for storage in sequential and 4k read/write and it goes from vista, 7, 8, 10 where vista has the best performance and win 10 has the worst for sata at least. every server OS version of that windows is faster than its consumer counter part.

lastly running pcie SSD on dmi 2.0 has no problem at all, just a lower out put at around 1.4-1.5GB/s sequential as long as your chipset is capable of higher performance and random takes hit too because 2.0 is 8/10 encoding which is a 20%, while 3.0 is 128/130 encoding much smaller performance loss.

going from tweaktown, check out their raid SSD SATA review on ivybridge system vs haswell system. both DMI 2.0 but haswell chipset is more powerful and allows higher sequential upwards 1.5GB/s while ivybridge system chipset only allows like 1.1GB/s max.
 

Unknown-One

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Yup, answered the question myself this evening. Here's an NVMe drive in the PCIe 4x slot provided via DMI 2.0:

cTtLCsw.png


What I was really curious about is how the OTHER devices on DMI would react with all the bandwidth being sucked up by an SSD. To me surprise. USB / SATA / Sound / NIC all kept working as expected.
It would appear that the chipset reserves about 500MB/s worth of bandwidth in order to prevent a high-powered add-in card from causing issues, even with an old DMI 2.0 board.

Moving it up one slot (putting it on the PCIe 3.0 lanes provided directly by the CPU) has it performing as expected, maxing out at 3.5 GB/s (but this drops my video card to PCIe 3.0 8x, which I don't want to do). I'll probably keep it on the DMI 2.0PCIe 4x slot :)
 
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Unknown-One

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going from tweaktown, check out their raid SSD SATA review on ivybridge system vs haswell system. both DMI 2.0 but haswell chipset is more powerful and allows higher sequential upwards 1.5GB/s while ivybridge system chipset only allows like 1.1GB/s max.
Hmm, interesting. I don't think the 1.1GB/s limitation with DMI 2.0 on Ivybridge holds up.

The test above was done on a Core i7 3770k installed in an Asus P8Z68-V/Gen3, and I was able to hit 1.5 GB/s in Crystal Disk Mark.
 

ryambo1987

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Hmm, interesting. I don't think the 1.1GB/s limitation with DMI 2.0 on Ivybridge holds up.

The test above was done on a Core i7 3770k installed in an Asus P8Z68-V/Gen3, and I was able to hit 1.5 GB/s in Crystal Disk Mark.
Hi Hardforums!

I've been searching for solutions to solve my NVME PcieX4 negotiated speed at V1. I want my NVME to run at PCIeX4 @ V2 Via PCH, but its limited to V1 for some reason. The processor is i7-2600 on a Asus "P8H67-M LE" motherboard. I would like to know your setup, in order to achieve 1600 MB/s read and write. However it's able to run at V2 in my CPU's PCie slot @ 1600 MB/s. The system in running windows 10 UEFI boot from NVME. I tried disabling all PCH PCIe devices and reseting CMOS battery, still runs at V1. MB has DMI 2.0 and NVME is limited to 800 MB/s on PCH PcieX4 V2 slot. The only difference I see in our setups is different PCH and Ivy bridge, but both support DMI 2.0 and is intel 6 series .
 

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