![]() But it's okay to leave those 4 pins disconnected because a motherboard with a 20 pin connector doesn't need them. The extra 4 pins were added to the 24 pin version of the cable to provide one extra wire for ground, 3.3, 5, and 12 volts. The 24 pin cable only fits into a 20 pin socket at one end so you can't plug it in incorrectly. The extra 4 pins on the cable just hang over the end of the motherboard connector. You can see an example in the picture above. If you have an ATX power supply with a 24 pin main cable, it's okay to plug it into a motherboard with a 20 pin connector. Unofficial cable/connector maximum wattage delivery for main rails Most newer power supplies don't provide -5 volts in which case the white wire is missing. Newer motherboards virtually never require -5 volts but many older motherboards do. The -5 volt line on pin 20 was made optional in ATX12V 1.3 (introduced in 2003) because -5 had been rarely used for years. These are pretty common on the 3.3 volt line in pin 13 but are sometimes used for other voltages too. Some of the voltage lines on the connector may have smaller sense wires which allow the power supply to sense what voltage is actually seen by the motherboard. The 24 pin connector is polarized so it can only be plugged in pointing in the correct direction. The extra pins made the auxiliary power cable unnecessary so most ATX12V 2.x power supplies don't have them. The new 24 pin connector added one line apiece for ground, 3.3, 5, and 12 volts. The older 20 pin main power cable only has one 12 volt line. The 24 pin main power connector was added in ATX12V 2.0 to provide extra power needed by PCI Express slots. The easy, and not so elegant, solution is to use a 4-pin Molex to SATA connector or a power supply equipped with SATA connectors that follow the SATA 3.3 specification.Standard 4.2mm Pitch ATX Header Connector Datasheet 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.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |