Hello Tom Yan,
Devslp is and addition to the AHCI (SATA) standards. Device Sleep is a feature that allows the host and device to coordinate turning off their respective PHYs (in order to conserve power). It requires the Host and the SSD to support it, both in Hardware and Firmware.
The best way to confirm if a specific device supports Devslp is to check with the manufacturer of the device: Computer Manufacturer Support
Here is a technical document that explains the Devslp feature:
Well it's not difficult to check whether the SSD supports it. I think you guys write it clearly in the spec and I can check easily in hdparm.
Thing is the ambiguous "host" you're talking about. Which part(s) of the "host" could be involved? Even if I should check it myself with the manufacturers, I don't know which parts I need to check. Should I ask Intel whether the CPU matters? Should I ask Intel about the PCH? Should I ask ASUS about my mobo? Should I ask AMI about my UEFI? Should I ask Seasonic about my PSU? Should I ask some factories in China about the power cables?
Hello Tom Yan,
According to the specification document in page 17, for a system to support Device Sleep, the device, the HBA and the system BIOS/driver all need to support Device Sleep. The SSD would be the device; if the rest of the components are embedded in the Motherboard, then the Computer Manufacturer Support (ie: ASUS) would be the best source to confirm Devslp compatibility; if you use an Add-in-card for Storage, then you would have to contact the HBA manufacturer as well.
The power supply and cables should be OK as long as they are in compliance with current Standards.