Slow Plotting on PCIe to NVME adapters

I have noticed that my onboard NVMEs perform close to twice as well than my NVMEs attached to a PCIE nvme adapter.

I have been using a combination of these three adapters.
when i do a benchmark on my drives they all show to have the same write rate 1.9GBPS

But when it comes to actually plotting i notice my onboard NVMEs out perform the once attached to the adapter significantly.

anyone else experiencing the same thing?

I am using a ryzen 5900 with 256GB of ram and a Gigabyte Aorus x570 motherboard (PCIE4) on Ubuntu 20

Here are a few of the PCIE adapters i have been using as well

1 Like

These are PCI-E 3.0 adapters. Of course you won’t get PCI-E 4.0 speeds.

Makes sense.

Plus, apples to apples assuming both were PCI-E 4.0, your onboard will always be faster due to trace length.

PLUS sharing of PCI-E lanes can also slow down certain devices on SATA, and even other NVMEs. Check your motherboard manual for more info there on bandwidth, although the X570 is pretty good in that respect.


And if you are using a x8/x16 lanes gpu it is eating lanes of pci-e. The onboard NVMe has a direct unshared x4 lanes.

… Might want to check in the 256GB of ram… Should max out to 128GB on ryzen 5000


all solid notes.
ill give the gpu advice a try. I do have a pretty solid GPU installed (cant remember the model at the moment, I have alot of hardware)
But I will get purchase a simple one and swap it out and see how it effects the plotting process.

speaking of the owning too much hardware. you are right, this build does only have 128GB of ram.
we have another build on in our farm with a threadripper pro 3975wx, that one has 256gb

pretty sure this is the second thread I have seen you in. thank you for help!

I get where you are coming from on the PCIE-3 thing, but PCIE has a ~ 1GBPS per lane throughput, giving the 8X throughput at ~8GBPS which is faster than the read/write of the NVME and wouldn’t see that causing the bottleneck .

The adapters you listed are PCI-E 3.0 x4. Not x8…

1 Like

Are u using single nvme PCI-e adapters that all use (share) the same lanes. Try benching ALL at the same time, and see results. Checked ur MB manual, doesn’t say anything about other cards/devices used cutting PCI-e bandwidth, but almost certainly will.

1 Like

well I started off with the second ones I sent you, which are 4x
but the first one I posted is has slots for 8x 16x, so are you saying the speed is still 4x?

a bit of a confusing question… are you asking if I am using a riser board or something like that?
or asking if my motherboard board shares a single PCIE bus for all PCIE slots, which I do believe is industry standard.

ill look into some MB settings for sure. but at the moment I am really only using 1 PCIE slot for NVME

I got similar ones (without the bracket though) but they somehow appear as PCIe 4.0 devices in the bios when I put 980 pro in them. Very confusing.

CrystalDiskInfo may report them as PCI-E 4.0 devices but I suspect the speeds will not be as such… I’d test and let us know if you are hitting speeds that PCI-E 4.0 would support, and if you are not… well then you are simply running in PCI-E 3.0.

1 Like

I might be out to lunch: In theory a pcie 3 gpu riser or nvme riser are just extension i think. So pci-e 4 speed is possible if signal crosstalk, noise and strength, etc. are within range.

As for gpu, i have a pcie 1x gt710 1gb( Thanks @Quindor ) in my e5- 2690v3 rig.

No Crystaldisk, but bios and lspci in linux both report 4.0. I will do some benchmarking.

These adapts seem to slot into the 1st x4 part of the PCI-e slot only, regardless of the physical length of the card. For example, I’m using two smthg like yours, so they share the avail bandwidth of one PCIE 3.0x4 (or 4.0 depending). Alternatively u can get this that gives each nvme its own x4, no sharing, however a bit $$$. There are some x8 cards as well for 2x nvmes. Since ur only using one card, ur not sharing, unless u have other cards, not nvme, using those same lanes.

Back to ur original issue, only other item I’m aware of is that MB connected nvmes goto the CPU directly, but PCI-e nvmes go thu a chipset controller, so the connection is not the same exactly. Pg 21 of this MSI x570 MB manual shows a block diag MSI USA that should be somewhat similar to your x570 MB.

1 Like

that is really good info bro. there seems to be 1 PCIE socket that is directly connected to the CPU. ill make sure my NVME is in that one.

that adapter is a little pricey but I might have to give it a whirl. thanks again.

1 Like

you’ve ben concisely showing up as well. I appreciate you bro!

1 Like

Good research, that’s the one to use!