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Old Oct 29, 2012, 10:25 PM   #1
Dr FranknFurter
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Location: Cambridge UK
Memory Upgrade 27" Late 2012 iMac

Just a quick look online reveals the following available from Crucial

Part Number: CT3650255
Module Size: 16GB kit (8GBx2)
Package: 204-pin SODIMM
Feature: DDR3 PC3-12800
Specs: DDR3 PC3-12800 CL=11 Unbuffered NON-ECC DDR3-1600 1.35V 1024Meg x 64

For 61 in the UK (or 31 for 8GB)

Now the standard iMac will ship with 8GB (2 x 4GB) so 2 slots used.

Meaning you can order in multiples of 8GB this means either 16GB or 24GB or if you want to go to 32GB you will need to remove the 2 x 4GB.

3 questions;

1. How is performance effected with split size memory modules, ie 2 x 4GB and 2 x 8GB? (i've heard conflicting opinions)

2. would we be able to sell the memory removed on here to other users who may like the idea of some cheaper memory to upgrade to 4 x 4GB ie 16GB total for less than the 31 above and keep all 4 modules the same size

3. Is there any dissadvantage to using different manufacturers, i.e Apple OEM supplied memory with say Crucial memory. This may also be a good reason to action item 2 above.

Thanks all and can't wait to get my first iMac
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Old Oct 30, 2012, 01:29 AM   #2
smoking monkey
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Quote:
Originally Posted by Dr FranknFurter View Post
Just a quick look online reveals the following available from Crucial

Part Number: CT3650255
Module Size: 16GB kit (8GBx2)
Package: 204-pin SODIMM
Feature: DDR3 PC3-12800
Specs: DDR3 PC3-12800 CL=11 Unbuffered NON-ECC DDR3-1600 1.35V 1024Meg x 64

For 61 in the UK (or 31 for 8GB)

Now the standard iMac will ship with 8GB (2 x 4GB) so 2 slots used.

Meaning you can order in multiples of 8GB this means either 16GB or 24GB or if you want to go to 32GB you will need to remove the 2 x 4GB.

3 questions;

1. How is performance effected with split size memory modules, ie 2 x 4GB and 2 x 8GB? (i've heard conflicting opinions)

2. would we be able to sell the memory removed on here to other users who may like the idea of some cheaper memory to upgrade to 4 x 4GB ie 16GB total for less than the 31 above and keep all 4 modules the same size

3. Is there any dissadvantage to using different manufacturers, i.e Apple OEM supplied memory with say Crucial memory. This may also be a good reason to action item 2 above.

Thanks all and can't wait to get my first iMac
Good questions. I'd like to know as well.
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Old Oct 30, 2012, 02:50 AM   #3
flynz4
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I'll be buying four 8GB modules to bring my total to 32GB. I'll store the two 4GB modules to replace in the event I need to send my iMac in for service.

/Jim
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Old Oct 31, 2012, 03:23 AM   #4
msg362
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Probably OK

I asked the same question of my son who is a wizard in Macs. He thinks it's probably OK ( it would normally be) unless Apple do something strange. My plan is to buy 16 GB from Crucial, add it and work out if it's OK. If not I'll remove the 2x4 Gb from apple and buy another 16 GB from Crucial and in the meantime run on 16GB
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Old Oct 31, 2012, 06:00 AM   #5
flatfoot
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Quote:
Originally Posted by Dr FranknFurter View Post
Just a quick look online reveals the following available from Crucial

Part Number: CT3650255
Module Size: 16GB kit (8GBx2)
Package: 204-pin SODIMM
Feature: DDR3 PC3-12800
Specs: DDR3 PC3-12800 CL=11 Unbuffered NON-ECC DDR3-1600 1.35V 1024Meg x 64

For 61 in the UK (or 31 for 8GB)

Now the standard iMac will ship with 8GB (2 x 4GB) so 2 slots used.

Meaning you can order in multiples of 8GB this means either 16GB or 24GB or if you want to go to 32GB you will need to remove the 2 x 4GB.

3 questions;

1. How is performance effected with split size memory modules, ie 2 x 4GB and 2 x 8GB? (i've heard conflicting opinions)

2. would we be able to sell the memory removed on here to other users who may like the idea of some cheaper memory to upgrade to 4 x 4GB ie 16GB total for less than the 31 above and keep all 4 modules the same size

3. Is there any dissadvantage to using different manufacturers, i.e Apple OEM supplied memory with say Crucial memory. This may also be a good reason to action item 2 above.

Thanks all and can't wait to get my first iMac
1. Performance is not affected.

2. Yes.

3. No.
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Old Nov 7, 2012, 10:58 PM   #6
Dr FranknFurter
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Quote:
Originally Posted by flatfoot View Post
1. Performance is not affected.

2. Yes.

3. No.
Coolio, thanks
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Old Nov 8, 2012, 02:00 AM   #7
MightyWhite
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I spoke to a chap at crucial (UK) and he said its best to keep them the same size so I am going to order 2X4 from there 31 delivered and then upgrade in the future if I use more than 16gb

The 4gb modules are not linked on the site yet but I can post the link later at work if you like
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Old Nov 8, 2012, 02:50 AM   #8
inwe
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Location: Spain
Hi,

My advice.. you can buy 2x8GB and get 24GB but I recomend to put the higher capacity dimms into the first two ram sockets, so you have to replace your 2x4GB for the new ones and put that memory into the free sockets.
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Old Dec 17, 2012, 11:00 PM   #9
MovieGuySly
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Mixing Crucial Ram with already installed 2x4GB Ram

I just ordered memory after long reading forums to find out the best one:

Crucial
16GB kit (8GBx2)
DDR3 PC3-12800 CL=11 Unbuffered NON-ECC DDR3-1600 1.35V 1024Meg x 64 Part #: CT3650258

However, when my iMac comes should I mix my new 16gb Crucial ram with the 8gb of preinstalled ram or just take the old one out?

I would like 24gb of ram but if it's gonna slow performance I will take the factory standard out.
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Old Dec 18, 2012, 06:19 AM   #10
BSoares
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Quote:
Originally Posted by MovieGuySly View Post
I just ordered memory after long reading forums to find out the best one:

Crucial
16GB kit (8GBx2)
DDR3 PC3-12800 CL=11 Unbuffered NON-ECC DDR3-1600 1.35V 1024Meg x 64 Part #: CT3650258

However, when my iMac comes should I mix my new 16gb Crucial ram with the 8gb of preinstalled ram or just take the old one out?

I would like 24gb of ram but if it's gonna slow performance I will take the factory standard out.
I did the same and now I have 24GB running at 1600MHz so you'll be fine too.
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Old Dec 18, 2012, 01:49 PM   #11
MovieGuySly
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Originally Posted by BSoares View Post
I did the same and now I have 24GB running at 1600MHz so you'll be fine too.
Have you gotten your iMac already? Did you buy crucial? And did you put the two 8GB ram sticks on the top slots?

Sorry, just wanna make sure I get this right.
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Old Dec 18, 2012, 02:30 PM   #12
edhawk1965
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Originally Posted by MovieGuySly View Post
Have you gotten your iMac already? Did you buy crucial? And did you put the two 8GB ram sticks on the top slots?

Sorry, just wanna make sure I get this right.
The factory ram on mine delivered yesterday was in the 2nd and 4th slots top to bottom, so I put the other 2 in the 1st and 3rd slots, worked fine at 1600mhz and recognized all 24gb.
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Old Dec 18, 2012, 02:30 PM   #13
BSoares
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Quote:
Originally Posted by MovieGuySly View Post
Have you gotten your iMac already? Did you buy crucial? And did you put the two 8GB ram sticks on the top slots?

Sorry, just wanna make sure I get this right.
Yes, Yes, No. I put the Crucial sticks in the empty slots. The iMac came with one on the bottom, skipped one, then another stick, then free slot. So basically slot 1 and 3 were used with stock Hynix memory, I put the Crucial sticks on 2 and 4. All running fine at 1600MHz.
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