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Is it OK to leave an internal hard drive's data cable connected to the computer motherboard but disconnect the power cable? Or will this damage the hard drive and/or the motherboard?

I've got a computer with two IDE hard drives in it which are rather noisy and I don't use them all the time so I'd like to disconnect them when I'm not using them but the data cables are difficult to connect and disconnect, so can I just disconnect the power?

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Yes you can just disconnect the power, and it won't harm anything.

Having said that, depending on your operating system, you should be able to configure the power saving features to shut down drives when not in use. This would avoid the need to physically disconnect them.

Are you really still using IDE? Does the motherboard support SATA. You'd probably find that a new SATA drive would be much quieter.

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  • I didn't want to use the power-saving features because I turn the computer on and off a lot as well, and it seemed like a waste having the hard drives powering up and down for like, 30 seconds, every time I turn the computer on when I'm not using them. Also this is an old computer so it doesn't support SATA but I use it for testing stuff and normally boot it from removable media; I have SATA in my current computer :-) . – Micheal Johnson Feb 18 '16 at 13:22
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I've done this in the past and it doesn't cause any problems. If the power cable is disconnected for only one of two IDE drives on the same data cable, you could run into issues with termination (depending which drive is where relative to the cable), but as long as both are powered down, the BIOS won't even detect them.

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  • I was thinking more of the "computer sending initialisation commands to drive without power" damaging the data interface on the drive by applying voltage to the data pins when there's no power to the interface controller. – Micheal Johnson Feb 18 '16 at 13:27
  • Ah. TTL or lower voltage on those pins of a powered-down drive board won't do any harm. at least in my experience. It's not like you were allowing static discharge voltages onto those lines. – Zeiss Ikon Feb 18 '16 at 14:26
  • Although static discharge is damaging even if the drive has power. I do know that some 4000-series logic ICs can be damaged if they are given input signals without power (and will tend to leak the signal voltage out through their outputs - incorrectly). – Micheal Johnson Feb 18 '16 at 15:00
  • I wasn't aware of that -- I'm not familiar with IC-specific or component-level electronics, and have no idea what's on a hard drive logic board. That, however, sounds like lazy design. You can't reasonably control what will be connected to the pins when the board is powered down. – Zeiss Ikon Feb 18 '16 at 15:14

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