I was just given an old iMac without a Hard Drive.

This is the model (image from the software Mactracker):

enter image description here

It only gives the following details about the hard drive:

320, 500, 750 GB, or 1 TB 7200-rpm

However, when I consulted ifixit to see how I could replace the hard drive, and clicked on the suggested replacement hard drive, some instructions said:

Important: To ensure compatibility with the 2009 and 2010 21.5" or 27" iMac, the replacement hard drive must be of the same brand as the original. The model number of the hard drive does not matter as long as the brand matches. 2011 and up iMacs cannot be supported by us.

Which doesn't help since I have the 2008 model. I am also not sure whether a 2.5 or 3.5 hard drive is required. The "About this Mac" menus are not available since the computer doesn't power on. I don't know what the RAM is (2.8 or 3.06).

What is the exact reference for a compatible model for this iMac Early 2008?

2 Answers 2


I'm going to try to answer your question as best I can.

  1. The drive is definitely a 3.5" SATA disk.
  2. The notice doesn't apply to your model.
  3. I'm not sure why the notice suggests to choose the same brand. For one, the drives are likely co-branded, with markings for both Apple and the company that made the drive. The companies that would have supplied the drives would be, AFAIK: Western Digital, Seagate and (possibly) Hitachi.
  4. I'm not sure how similar you have to go in terms of storage. I'd guess you could probably use any SATA drive, but because of the temperature sensor, if I were you, I'd use one of the ones suggested in the guide, depending on your storage requirements (1-4TB).

TL;DR: If you're super worried about compatibility and need to get the machine working fast, disassemble it and look at the HDD to determine the brand, then order that brand. Otherwise, I would suggest you buy whichever of the listed HDDs strikes your fancy - I doubt that it really matters.

  • Thank you for this answer! It doesn't have a hard drive, so disassembling it will only tell me the size of the hole where it should go! heheh. However, I have a couple of old WD Caviar 3.5 drives at home but I thought these needed external power (in addition to USB) to work? (8 pin plug). I also would have no idea how to fit the temperature sensor if I used those. Apr 19, 2017 at 1:48
  • 1
    You sure, @MicroMachine? I think generally it's either SATA power or Molex power. If you have time on your hand, you can try it out!
    – NoahL
    Apr 19, 2017 at 1:53
  • The ones I have have this weird 8 pin plug - the instructions on iFixit do not mention them. I thought this meant external power is needed? Apr 19, 2017 at 2:15
  • Oh don't worry about that @MicroMachine. Many SATA disks have them and I've never plugged anything into them.
    – NoahL
    Apr 19, 2017 at 2:25
  • Thanks! Do I need to reformat it before I put it in or can it be done afterwards? Apr 19, 2017 at 21:56

The only tricky bit I've seen is where some SATA2 controllers in that era had an issue with most brands of SATA3 SSDs. Not sure about the iMac but I encountered it on a 2009 MBP.

Based on the Macsales/OWC page, your iMac will have a 3.5" space so if you use a 2.5" drive, you'll need a caddy.

Doing this on an iMac isn't for the faint of heart so watch the OWC install video for an SSD (it will be the same process for a spinner) and make sure you have the exact tools required. Those tiny screws are easy to strip if you try to use something "close enough". If you can at all swing it, I'd install a 480GB OWC SSD instead of a spinning drive as it's going to run much, much better. Even if you go for a spinner, I'd talk to OWC first and spend the extra few bucks to get one from them. If you encounter an issue, their tech support is good.


Installing an old 3.5" drive would be way down my list. Hotter, slower, and less reliable than any new drive.

  • Unfortunately, I don't have the budget for a SSD right now, a "spinner" will have to do! Apr 19, 2017 at 4:35

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