Q: can imac (late 2011) support 1666mhz ram ?

No, it cannot.

No. Buy the specified ram from a reputable vendor such as Crucial or OWC or you're asking for problems.

Supports 1333 MHz PC3-10600 DDR3 SO-DIMMs.

I think you are referring to the Mid 2011 iMac, right? The Mid 2011 iMac uses DDR3 1333 MHz RAM, so you can only use this type of memory with your Mac. See > http://support.apple.com/kb/HT1423?viewlocale=en_US#1

You can buy the memory in OWC or Crucial. Both provide compatible memory with your Mac, so you don't have to worry about compatibility issues. Crucial is a bit cheaper than OWC with memory

Mac's are very picky and that model takes PC3-10600 RAM.

You need:

• PC3-10600
• Unbuffered
• Nonparity
• 204-pin
• 1333 MHz
• DDR3 SDRAM

See > iMac (Mid 2011): Memory specifications

It looks like a Kappy's error (everyone has got errors). The Mid 2011 iMac supports 16 GB of memory officially (4x4 GB), but you can install 32 GB of memory (4x8 GB) if you want this amount of RAM

It will actually support 32gb. http://www.everymac.com/systems/apple/imac/specs/imac-core-i7-3.4-27-inch-alumin um-mid-2011-thunderbolt-specs.html

You are welcome

Its memory is from Crucial.

You can use the brand you want, always that you buy it from OWC or Crucial. As it doesn't mind (if you meet what I have told you), you can buy the cheaper you find in OWC or Crucial without any problem

Sorry, I thought you had the Late, not the Mid model.