Watch Out for SATA III Drives in SATA II Macs and PCs

SATA standards are all backwards compatible, right? Well, not necessarily. Researching upgrade options for the 2010 iMac on my desk has been a real learning experience. Some SATA III hard drives are auto-sensing and thus compatible with SATA II and SATA I ports, but some SATA III hard drives are fixed speed only and thus not backward compatible with SATA II Macs (and PCs) unless you can add a SATA III card.

It does work the other way. You can put a SATA II hard drive in a SATA III computer, and it will work just fine. The hardware on the logic board handles that. But to trim the cost of producing hard drives, several manufacturers have switched to fixed-speed SATA III drives. And that’s not a problem for most computers built since 2011.

That is a problem if you’re trying to use a fixed-speed SATA III drive with a SATA I or SATA II computer, such as this iMac. Here’s a list of SATA Macs that don’t have SATA III and are thus not compatible with fixed-speed SATA III drives:


  • iMac G5
  • iMac, Intel, 2006 models
  • MacBook, 2006-Late 2008 polycarbonate
  • MacBook Air, Late 2008-2009
  • MacBook Pro, 2006-Early 2008 + Late 2008 17″
  • Mac mini, 2006-2007
  • Xserve G5, all versions


  • iMac, Intel, 2007-2010
  • MacBook, Late 2008 aluminum-2010
  • MacBook Air, 2010
  • MacBook Pro, Late 2008-2010 (except for the Late 2008 17″)
  • Mac mini, 2009-2010
  • Mac Pro, 2006-2012
  • Xserve, all Intel versions

You’re going to want to check the spec sheets carefully before buying a SATA III hard drive for any of the Macs listed above. If they support earlier SATA protocols they will usually claim speeds of 6 Gbps, 3 Gbps, and 1.5 Gbps. If they don’t, be aware that they may not work with older Macs, PCs, or drive enclosures.

I have not heard of this being an issue with SSDs, which tend to be more expensive and thus give the manufacturer less incentive to cut corners, but it’s every bit as likely to show up in SSDs to keep prices down as it has been in spinning platter hard drives.

As they say, Let the buyer beware.

Forewarned is forearmed.

keywords: #satai #sataii #sataiii #sataiiionly #fixedspeedharddrive

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