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24GB RAM? Late 2012 27" iMac

virginblue4

virginblue4

macrumors 68020
Original poster
Apr 15, 2012
2,036
727
United Kingdom
I plan on purchasing 16GB crucial RAM for my late 2012 27" iMac when it arrives.

I don't plan on getting rid of the 8GB stock RAM that the iMac comes with. Can I just combine 2 8GB sticks with 2 4GB sticks?

Will there be any performance problems or will it be detrimental to the long term health of my iMac?

Many thanks!
 
Same as above. Been running it since day one back at the beginning of January. No problems at all
 
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zonesey said:
Yes, there will be a decrease in RAM clock speed due to inconsistent latencies. The 24 GB RAM will most likely have (and be shown with) a bandwidth of 1333 MHz instead of 1600 MHz.

See this quick explanation: http://www.amazon.com/review/R2TP3TRS894V7G/ref=cm_srch_res_rtr_alt_1

Nonetheless, this is not a major concern for most users :cool:

-J
Click to expand...

There is so much wrong with this post it is not even funny...
As long as you buy unbuffered non-ecc ddr3-1600 with a cl of 11 you are good... If you buy faster latency ram (cl 10 or cl 9) it can slow the bus speed to 1333 mhz... Crucial's website will tell you what ram to buy to match the stock ram...
 
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seanm9 said:
There is so much wrong with this post it is not even funny...
As long as you buy unbuffered non-ecc ddr3-1600 with a cl of 11 you are good... If you buy faster latency ram (cl 10 or cl 9) it can slow the bus speed to 1333 mhz... Crucial's website will tell you what ram to buy to match the stock ram...
Click to expand...

True, but the point is that the bus speed can be decreased to 1333... So, be careful what you buy :)
 
virginblue4 said:
I assume this is the correct RAM?

http://www.crucial.com/uk/store/mpartspecs.aspx?mtbpoid=CFFEC046A5CA7304
Click to expand...

Personally, I wanted to max out the RAM (32GB), so I didn't (need to) worry about compatibility with the Apple RAM.

It doesn't seem to be all that simple all the time. See this for example:
https://discussions.apple.com/message/21056039#21056039

Anyway, hope my posts help... You never know what kind of flak you might get if you open your mouth on this forum :D
 

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I have just added 16gb Crucial ram to my new iMac 27.. although I read on here somewhere to put the 2 x 4gb ram in the spare 2 slots and insert the 2 x 8gb ram in the 4gb slots (if that makes sense). So my setup is 4,8,4,8 as you look at it from behind

Works great so far
 
I'm running on 2x8GB and 2x4GB right now and my RAM speed drops to 1333MHz. Not to worry as I ordered another 2x8GB to make mine 32GB at 1600MHz.

Moving my 8GB to a 2010 13" MBPro. Hopefully it takes.
 
zonesey said:
True, but the point is that the bus speed can be decreased to 1333... So, be careful what you buy :)
Click to expand...

Your post said "there will be a decrease" not "can be if you get the wrong kind", hence the erroneous information.

If the OP uses the crucial adviser, there will not be an issue. From another thread, the recommended procedure from Apple is to remove the two 4 gig sticks, replace them with the 8 gig sticks, then put the 4 gig in the remaining two slots.

That is what I did. There is no decrease in speed, system sees 24gig and I have not run into issues.
 
robjulo said:
Your post said "there will be a decrease" not "can be if you get the wrong kind", hence the erroneous information.

If the OP uses the crucial adviser, there will not be an issue. From another thread, the recommended procedure from Apple is to remove the two 4 gig sticks, replace them with the 8 gig sticks, then put the 4 gig in the remaining two slots.

That is what I did. There is no decrease in speed, system sees 24gig and I have not run into issues.
Click to expand...

This is what I did, cant go wrong unless crucials website is wrong..

PS how are you guys monitoring the ram speed to see what you are getting?
 
gaddster said:
This is what I did, cant go wrong unless crucials website is wrong..

PS how are you guys monitoring the ram speed to see what you are getting?
Click to expand...

Apple logo in top left > About this Mac > More Info > System Report > Memory

This will show you the slots used, size of the memory and speed
 
Great thanks

Yep, mine stating a glorious 24gb at 1600MHz

Out of curiosity, is there any difference with the way i have my slots i.e.

Bank 0 8gb
Bank 1 8gb
Bank 0 4gb
Bank 1 4gb
 
I'll look when I get home tonight to see how mine are laid out.

I did do the recommended process (at least the post I referred to indicated it was the Apple recommended process), in that I removed the 4 Gig Sticks, replaced those sticks with the 8 Gig sticks in the slots that previously contained those 4 Gig Sticks and then put the 4 Gig Sticks back in the remaining open slots.
 
robjulo said:
I'll look when I get home tonight to see how mine are laid out.

I did do the recommended process (at least the post I referred to indicated it was the Apple recommended process), in that I removed the 4 Gig Sticks, replaced those sticks with the 8 Gig sticks in the slots that previously contained those 4 Gig Sticks and then put the 4 Gig Sticks back in the remaining open slots.
Click to expand...

Cool thats what I did, so think I have done it right :D
 
I ordered this:

http://amzn.com/B008LTBJFW

And put them both into the empty slots. Didn't move the Apple RAM.

My system says 24 GB, all running at 1600 Mhz (or whatever unit it is).

No crashes or issues in the past few days.
 
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RAM/slot configuration for 24GB

iMaxIt said:
http://www.crucial.com/uk/store/partspecs.aspx?IMODULE=CT2KIT102464BF160B

(Make sure it's for Mac)

Im using this one. I removed the original RAM and replace with Crucial RAM. Then I inserted the original in 2 blank RAM slots left. System said 24Gb RAM, 1600 each. :rolleyes:
Click to expand...

This is the correct RAM placement.

The new RAM must be inserted where the original Apple RAM was located.

The processor goes to those slots first, so it will see and use the new 16GB first and not use the old 8GB unless needed for more than 16.
 
gaddster said:
Great thanks

Yep, mine stating a glorious 24gb at 1600MHz

Out of curiosity, is there any difference with the way i have my slots i.e.

Bank 0 8gb
Bank 1 8gb
Bank 0 4gb
Bank 1 4gb
Click to expand...

Mine is showing the same as yours.
 
gaddster said:
Great thanks

Yep, mine stating a glorious 24gb at 1600MHz

Out of curiosity, is there any difference with the way i have my slots i.e.

Bank 0 8gb
Bank 1 8gb
Bank 0 4gb
Bank 1 4gb
Click to expand...

I moved 1 of the 4GB sticks into the other bank before installing mine ... so i have the banks matched .... doesn't make massive difference though
 
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