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I have a Dell Precision T3610 workstation that currently has two 3.5" SATA HDDs installed, and I'd like to add two more 2.5" disks in a hot-swap bay. I have two free SATA ports, but I'm struggling to find a way to provide power for the additional drives.

The only spare power connector on the PSU is an 8-pin PCIe block designed to provide power for a second graphics card. The machine has a 685W power supply - my intuition is that if the PSU is designed to provide enough power for a second graphics card then it should probably be able to handle a couple of extra 2.5" HDDs (which would should only draw about 3-4W apiece) but I admit that I have not done all of the math to confirm this.

I've come across various SATA-to-PCIe power adaptors (e.g. this), but so far I haven't found the converse (i.e. male PCIe to female SATA). I suspect that there is a good reason for this - my understanding is that PCIe power connectors provide ground and +12V pins, whereas SATA also requires a +5V pin (and possibly +3.3V as well for old drives). Can anyone confirm whether my suspicions are correct, and it is impossible to power a SATA drive from a PCIe connector?

Another possibility I'm considering is whether I can use a couple of y-adaptors to split the power supply to my two existing 3.5" HDDs in order to provide power for the two additional drives. Does this sound like a reasonable approach to try?

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    I think the Y adaptors are your best solution. It is also the cheapest solution. – whs Mar 29 '15 at 17:15
  • I am still searching for a PCI-e 6 or 8 pin power adapter to 15 pin SATA power. The y-adapter is a start but not the perfect / ideal solution since the power draw needs to be kept in check. – anon58192932 Apr 27 '17 at 19:08
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The y-adapter is reasonable, and something you can calculate beforehand.

The HDD manufacturer should provide a product specification listing the maximum amperage draw for the rails it uses (example). A power connector supplies a total of 4.5 A for each voltage, so knowing if you have enough power is something you can check

Usually 3.5" drives use the 12V rail or both the 12V and 5V rail, and 2.5" drives just the 5V rail.

The 3.5" drives will draw more current, and some drives can draw more than 2.25 A, so it may be better to put them on different y-cables. Using the y-cable for a 3.5" and 2.5" is probably nothing to worry about at all.

  • Thanks Louis, the y-adaptors are, at the very least, a partial solution for my problem. With the y-adaptors I am currently able to read/write to HDDs in both of the hot-swap bays provided that the disks were present at boot-time, and I am also able to unmount and remove them using this tool. However, I have not been able to get the OS to detect a new disk if when it is inserted after booting. I suspect this may be a Windows issue rather than a hardware issue, so I'm marking your answer as accepted. – ali_m Apr 6 '15 at 23:03
  • @ali_m Hmm, are you only slitting the power? – Louis Apr 6 '15 at 23:04
  • Yes. Unfortunately the cables were not long enough to be able to share power between one 3.5" and one 2.5" drive, so I'm currently running both 3.5" drives from a single y-cable, and both 2.5" drives from the other. It's not an ideal state of affairs, but based on my calculations the single power cable should be able to provide just enough current to run both of them (I've also run some SMART tests on the 3.5" drives, and I'm not seeing any errors). – ali_m Apr 6 '15 at 23:12
  • It might potentially be some weird motherboard/BIOS issue. I've set the SATA mode to AHCI, and naively assumed that anything supporting AHCI would probably also support SATA hotswapping. Now I'm not so sure. Dell don't seem to provide any information about this (I've asked on their Community forums as well, but no responses so far). I also can't rule out whether the problem is OS-related. – ali_m Apr 6 '15 at 23:15
  • @ali_m Sorry if you wasted money/time. Are you sure you're not using a RAID setup? This would cause them to be visible in pre-boot but not in Windows. – Louis Apr 6 '15 at 23:39
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It doesn't exist, at least not as a simple cable.

PCIe power connectors only provide 12V. Drives nearly always need 5V and sometimes also need 12V.

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