Poor performance with Samsung SM951 AHCI SSD

[Fernando]

@Lebedev

Can you explain to me how to attach an AHCI capable storage device directly via PCI Express? There MUST be a SATA Controller in between.

There is defnitively a SATA AHCI Controller in between. The related HardwareIDs are within the picture you have just posted.

[Lebedev]

Nice, so now you agree that it’s a SATA device. Do you also agree that this SATA Controller is inside the SSD?

[Fernando]

@Lebedev

Nice, so now you agree that it’s a SATA device. Do you also agree that this SATA Controller is inside the SSD?

I never had a doubt about it, but a SATA Controller is not a Disk Controller.

[100PIER]

@Lebedev
The performances I get with SM951 AHCI 512GB plugged on PCIe Gen 3 are quite good:

Meltdown/Spectre protection disabled:

Meltdown/Spectre protection enabled:

When plugged on a PCIe Gen 2 instead of Gen 3 the performance is obviously low:

[Lebedev]

@Fernando

I never had a doubt about it, but a SATA Controller is not a Disk Controller.

I didn’t say that anywhere. But you can’t connect multiple NAND flash chips to a SATA controller. You can’t connect a spinning hard drive to a SATA controller. There’s always i disk controller in between, which controlls the NAND chips or the Platter+Head. Do you agree on that?

[Fernando]

@Lebedev

You can’t connect a spinning hard drive to a SATA controller. There’s always i disk controller in between, which controlls the NAND chips or the Platter+Head. Do you agree on that?

No, unless you show me the additional Disk Controller listed within the Device Manager.