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macrumors newbie
Original poster
Aug 28, 2020
Hi everyone,

I have a 2011 27" A1312 iMac. I have replaced the superdrive with an SSD, and now I am looking to remove the hard drive that the imac came with, however I have one question.

If I remove the hard drive without putting anything in the slot, will the fans run at 100%? I know this happens if you use a third party drive but I just want to be sure.



macrumors newbie
May 26, 2018
Probably yes
I had yesterday the same thing
Ssd in dvd and ori hdd changed to third party with in line temp sensor.
Result was every 2 or 3. Boot failed.
It seems imac looking always the ori sata port for booting.
At the end i mounted ssd on ori sata with in line temp sensor and put back dvd

Juicy Box

macrumors 604
Sep 23, 2014
There are plenty of threads about the various results when swapping the HDD for a SSD (although nothing definitive), I don't see how leaving it unplugged would be any different than swapping with a SSD.

People add sensors and use them external to the SSD, I don't see why you couldn't do the same (just without a SSD). I have also see people shorting the pins with the temp sensor, which might be an option for you.

But, why not swap the SSD that is using the ODD SATA cable for your HDD?

You may see a performance increase by swapping your SSD with the HDD, as the only ODD is SATA2, IIRC.

Then just use an external temp sensor solution or SW solution to control the fans.


macrumors 6502
Apr 15, 2020
You may see a performance increase by swapping your SSD with the HDD, as the only ODD is SATA2, IIRC.
That is correct.

So replacing the superdrive is sub-optimal. No only is this SATA port slower (SATA2), you alsoblock the air flow to the GPU which, in the 27", is often dieing early. Less obstruction in the air flow could be beneficial (even though this may not be proven yet).

If you want to take out the HDD, you can apply the HDD jumper as what Apple does in the original HDD-free (SSD-only) configuration.
This is also described in the service manual.
This thread here describes it.
So bridge pin 2 and 7, and the fans will run on standard seed (~1000 rpm).

So what to do with the SSD? - Normally, you remove the logic board and connect it to the SSD SATA connector which is located on the board. If you connect it to the HDD connector (second best choice, since it supports SATA3 speeds, too), you could bridge the temp pins.
Again, see here for details.
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