Model A1286. Released February 2011 / 2.0, 2.2, or 2.3 GHz Quad-core Intel Core i7 Processor

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Laggy on Mac OS, but not on Bootcamp.

Hey everyone,

Specs: i7, 16gb of ram

I replaced my hard drive with a Samsung Evo since I thought the hard drive was damaged. I also replaced the cable. It'll start off okay on the Sierra OS side, and then start lagging terribly. I then struggle to shut down the computer because moving the mouse and clicking becomes very sluggish. Absolutely do not have this problem on the Windows 7 part of the hard drive. I can use the computer fine for hours. Any idea what this might be?

Thanks, much appreciated

Answered! View the answer I have this problem too

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Before getting deeper into possible hardware problems I'd try the easy road by creating a new user, logout from current user and log into the new one. If the lag is still there then it's possibly a system issue or a hardware problem. Try also resetting PRAM by pressing together command+option+P+R at startup until you hear a second boot chime.

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Hi Abraman,

Thanks for replying. I've tried to create a new user, and resetting the PRAM. It didn't solve the issue. It's weird because I can use the Windows partition without any issues. I don't really mind, but it'd be nice to be able to use the Sierra partition as well.


In order to rule out a possible system issue a clean Os install would definitely be a troubleshooting option. Other than that, we would probably get into a hardware failure. There's a number of machines with your specifications having shown similar symptoms after an hard drive or a battery replacement. If you have the original install disk you could try a hardware check and see if that exposes a problem. It might be a temperature sensor returning invalid infos to your Mac and keeping your processor busy with a kernel task it cannot complete properly. If you manage to open the activity monitor to list all running processes you'll probably find a stuck kernel task process sucking all computing capacity. Such instructions set is not present in the windows Os, therefore it runs properly in bootcamp.

Let's see first if a clean system install fixes the issue.


My buddy reinstalled the OS. He eventually took out the battery and it's running ok now. It's throttling the processor and GPU from what I understand without the battery, so got a new battery on the way. Hope that's all that needs to be done.


If you get a good battery, problem will be probably solved. Not so unusual battery logic or sensor goes bad and causes Cpu throttling.


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It sounds like a reinstall of Sierra might help, give it a shot.

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gary will be eternally grateful.
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