![]() This is because P3 driven HIGH will prevent the drive from powering up. All drives with this optional feature will not power up if a legacy SATA connector is used. If P3 is driven HIGH (2.1V-3.6V), the power to the drive circuitry will be cut. To sum up, for products supporting the optional SATA 3.3 power disable (PWDIS) function, the third pin (P3) of the SATA connector is now assigned as the Power Disable Control pin. You will find more information about the PWDIS feature in this tech brief. Further, if you're looking to buy HDDs for NAS servers, you should also pay attention to this issue and check to be sure your hardware is PWDIS compatible. Some companies also offer the corresponding products in two versions, one with PWDIS support and one without, in order to avoid compatibility problems. This adapter will remove the 3.3V signal from P3 of the SATA connector, and the HDD will start normally however, there will be no PWDIS support.Ĭurrently, there are a number of HDDs supporting the power disable feature, and that number will only continue to grow. You can totally bypass the 3.3V rail (which after all isn't used in HDDs) by using a simple 4-pin Molex-to-SATA adapter to supply power to the HDD. ![]() The combination of legacy SATA connectors with new HDDs supporting the PWDIS feature can cause major headaches to users, but the fix is easy, at least if you don't have many of those new HDDs to power. It will get stuck in a hard reset condition, which will prevent the HDD from spinning up. This means that if you combine a PSU with the older SATA connectors, featuring 3.3V at P3, and a new HDD that supports the power disable feature, the HDD won't ever start because it will see a continuous high-state signal on P3. According to the newer SATA specs, P3 is now independent and transfers the power disable signal. This feature utilizes the third pin (P3) of the SATA connector, which in the older SATA specifications is tied to the first (P1) and second (P2) pins, and all of them carrying the 3.3V rail to the drive in use.
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