Memory for late 2009 iMac (21.5 Inch)

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Memory for late 2009 iMac (21.5 Inch)

I have a late 2009 21.5" iMac and I want to figure out what time of memory to purchase for an upgrade. When I look at the information in 'About This Mac>Memory' it states that "Your Mac contains 4 memory slots, each of which accepts a 1067 MHz DDR3 memory module." (see attached image)

However, when I click the link where it says "Memory Upgrade Instructions," it takes me to the site http://support.apple.com/kb/HT1423?viewlocale=en_US#1

On the site, its states that "For the iMac (Late 2009) models, you can use 2 GB or 4 GB RAM SO-DIMMs of 1066 MHz DDR3 SDRAM in each slot"

Which one is correct? The 1066MHz or 1057MHz?

iMac, OS X Mountain Lion (10.8.2), 21.5 Inch, Late 2009 Model 10,1

Posted on Oct 1, 2012 2:09 PM

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Answer 1

BDAqua

Level 10

250,409 points

Oct 1, 2012 3:43 PM in response to April E.

Hi April,

PC8500 DDR3 1066MHz SO-DIMM 204 Pin Memory Upgrade Kit for all Apple iMac 21.5" and 27" (October/2009) Models.

Technology: DDR3 SDRAM
Density: 4GB (4096MB)
RoHS: Yes
Pin Count: 204-pin
Op. Temp.: 0C to +85C
Data Rate: DDR3-1066
Speed: PC3-8500
CL: CL = 7
Cycle Time: 1.875ns
Voltage: 1.5V
ECC: Non ECC
Module Ranks: Dual Rank
Register: Non Parity
Low Noise 8-Layer PCB
Meets and/or Exceeds Apple/Intel Specifications

http://eshop.macsales.com/item/Other%20World%20Computing/8566DDR3S16S/

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Answer 2

Oct 7, 2016 11:54 AM in response to April E.

Hey April,

Sorry for adding on to such an old thread, but I just saw this post while searching for a similar issue.

And thanks to BDAqua for posting all of that detailed info. Good stuff.

But despite all the info, I'm not sure it answered your question.

You asked which is correct, the 1066 MHz, or the 1067 MHz, right? (I'm guessing 1057 was a typo)

The answer is that both are correct. They are both the same. The actual speed of that particular memory is 1066.6666(repeated). Some manufacturers round that to 1067 while others truncate it to 1066, but in either case it is the same speed.

The important thing is that you get DDR3 SO-DIMM 204 pin.

This being such an old topic, I'm guessing (hoping) you've solved the issue by now, but for anyone else searching similar issues, I just wanted to throw that out there.

Hope this helps.

And just as an aside, even if you got the faster 1333MHz memory, it will run perfectly fine in that particular iMac, so long as it meets all the other specs - despite Apple's reluctance to say so. (Virtual all RAM memory is backwards compatible concerning speed)

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