SN850 only 900mb/s

[Adrucito]

I recently installed a WD SN850(Gen4 x4) on a Gen2 x2 port (I have a H310M M2 2.0 motherboard), and it's only outputting really slows speed, i know that i have a older generation port, but is it normal for it to be that slow?

 

[Tech_Magnus]

Since your port maxes out at 1000 MB/s, those values are valid.

PCI Express - Wikipedia

en.wikipedia.org

 

[Speedyblupi]

Why would you use a flagship PCIe 4.0 NVMe SSD on an old entry-level motherboard? I guess it doesn't hurt if you'll move the drive to a PCIe 4.0 system in the future, but seems like an odd choice to me.

 

[Chrispy_]

I recently installed a WD SN850(Gen4 x4) on a Gen2 x2 port (I have a H310M M2 2.0 motherboard), and it's only outputting really slows speed, i know that i have a older generation port, but is it normal for it to be that slow?

Yes. Gen2 x2 is 1/8th the bandwidth of Gen4 x4.

900/1800/3600 MB/s are the real-world sequential maximum speeds for x1, x2, and x4 ports respectively. a Gen2 x2 is the same bandwidth as a Gen3 x1

If you can put it into a faster slot then you should but don't get too hung up on it if you can't do that because the sequential speeds really aren't that important unless you're regularly reading and writing huge amounts of data to or from it from other fast storage, or video editing on that drive.

When using it as an OS drive the most important thing is 4K random performance at low queue depths and this will never get close to even the 900MB/s limit your Gen2 x2 slot is providing. Excellent SSDs can manage maybe 100MB/s in this metric and "good", editor's choice award-winning SSDs will often only manage 50MB/s in a 4K random QD1 test. That PCIe Gen2 x2 bottleneck really isn't an issue 99% of the time.

Loading applications/games/saving files is usually limited by the compression/decompression performance of your CPU and unless you end up swapping to disk a lot due to a shortage of RAM, you're unlikely to push sequential bandwidth outside of mass media copying, video editing, or synthetic benchmarks.

 

[Adrucito]

Yes. Gen2 x2 is 1/8th the bandwidth of Gen4 x4.

900/1800/3600 MB/s are the real-world sequential maximum speeds for x1, x2, and x4 ports respectively. a Gen2 x2 is the same bandwidth as a Gen3 x1

If you can put it into a faster slot then you should but don't get too hung up on it if you can't do that because the sequential speeds really aren't that important unless you're regularly reading and writing huge amounts of data to or from it from other fast storage, or video editing on that drive.

When using it as an OS drive the most important thing is 4K random performance at low queue depths and this will never get close to even the 900MB/s limit your Gen2 x2 slot is providing. Excellent SSDs can manage maybe 100MB/s in this metric and "good", editor's choice award-winning SSDs will often only manage 50MB/s in a 4K random QD1 test. That PCIe Gen2 x2 bottleneck really isn't an issue 99% of the time.

Loading applications/games/saving files is usually limited by the compression/decompression performance of your CPU and unless you end up swapping to disk a lot due to a shortage of RAM, you're unlikely to push sequential bandwidth outside of mass media copying, video editing, or synthetic benchmarks.

Thank you so much, really neat information.

 

[The red spirit]

When using it as an OS drive the most important thing is 4K random performance at low queue depths and this will never get close to even the 900MB/s limit your Gen2 x2 slot is providing. Excellent SSDs can manage maybe 100MB/s in this metric and "good", editor's choice award-winning SSDs will often only manage 50MB/s in a 4K random QD1 test. That PCIe Gen2 x2 bottleneck really isn't an issue 99% of the time.

The original advantage of SSDs was massive IOPS and super short "seek" times, despite them (at first) lacking sequential performance. That's why even converted to IDE connector, SSDs delivered tons more performance. That didn't really change in a decade.