hesela.devSATA Power Disable (PWDIS)
SATA Power Disable is an optional feature using power-connector pin P3 to control power to device circuitry when supported and enabled.
Support, current enablement and always-enabled implementations are distinct. Power Disable and Device Sleep share P3 and are mutually exclusive. A supported feature need not be permanently active. [1]
For supported devices that are not always enabled, a power-on reset disables the feature; hardware and software resets leave its enablement unchanged. Always-enabled devices retain it across resets, and a request to disable it is aborted. [1]
When enabled, PWDIS allows power with the input negated or unconnected at the host connector; disabling power and resetting the device depend on the specified signal levels and timing. [1]
In documented PWDIS-equipped HDD variants, a legacy supply holding P3 at 3.3 V prevents spin-up. Check the exact drive variant and enclosure wiring: this compatibility condition does not by itself establish drive failure. [2]
Link power management is separate: Partial and Slumber reduce PHY activity without determining whether an HDD spindle is rotating. A low-power link is not evidence that device circuitry has been power-disabled. [3]
Relations
Advantages
- A compatible chassis can power-cycle a supporting and enabled drive without physical removal. [2]
Limitations
- A mechanically fitting SATA connector does not establish PWDIS electrical compatibility. [2]
Citations
- SATA-IO Serial ATA Revision 3.5 Gold (1 July 2020), sections 8.6, 13.3.12, 13.7.11.2.16 and 13.7.11.3.10
- Western Digital: Power Disable Feature technical brief, pages 1-3 (Ultrastar product-specific evidence)
- Intel: Designing Energy Efficient SATA Devices, revision 1.63, April 2011, sections 2-2.3
Sources & caveats
- Specification-based explanation, not a hardware experiment. The compatibility example concerns Western Digital Ultrastar variants in the cited brief, not a current compatibility list. [2]