27" RAM Upgrade - why not 24GB?

[bflowers]

I'm asking an Apple rep right now. hold on..

Edit:
Couldn't answer that, as they are specifically versed in the options available in their online store. Directed me to call 1-800 My-Apple and pick the Mac Experts line. I'll do that if I get a chance, but since I live near an Apple Store, I might just ask the next time I run over to that mall.

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It will certainly be less than 50% just trying randomly. But in reality it will be either 8/4/8/4 or 8/8/4/4.

My guess is the 8/8/4/4, as they would have the preinstalled ram split between the two channels, but that is a guess. Off the top of my head, I'm going to say 33% chance strictly speaking, as a third install option (which I really doubt) is a/b/b/a.

 

[lixuelai]

I'm asking an Apple rep right now. hold on..

Edit:
Couldn't answer that, as they are specifically versed in the options available in their online store. Directed me to call 1-800 My-Apple and pick the Mac Experts line. I'll do that if I get a chance, but since I live near an Apple Store, I might just ask the next time I run over to that mall.

----------



My guess is the 8/8/4/4, as they would have the preinstalled ram split between the two channels, but that is a guess. Off the top of my head, I'm going to say 33% chance strictly speaking, as a third install option (which I really doubt) is a/b/b/a.

I actually changed my estimate to 100%. You are guaranteed to get it right since Apple already installed 2 sticks in dual channel for you

 

[bflowers]

I actually changed my estimate to 100%. You are guaranteed to get it right since Apple already installed 2 sticks in dual channel for you

that's my feeling, but I'm on hold with Apple to make sure. I'm feeling helpful, and I have the time to get the community an answer.




Edit: The Apple rep confirmed this. So just fill your empty slots with whatever you are wanting to put it.

 

[Foxer]

So does anyone have a coupon code for Crucial?

 

[blastair]

So does anyone have a coupon code for Crucial?

You can click through a RetailMeNot link for 5% off and free shipping. Not the greatest deal in the world, but better than nothing.

 

[bgsnmky]

that's my feeling, but I'm on hold with Apple to make sure. I'm feeling helpful, and I have the time to get the community an answer.




Edit: The Apple rep confirmed this. So just fill your empty slots with whatever you are wanting to put it.

so either purchase the 2x8GB - and put in the empty slots....and it would be 24.00

or spend another 75.00 and take the 2 that come with the imac and replace all of them..

right?

 

[bflowers]

so either purchase the 2x8GB - and put in the empty slots....and it would be 24.00

or spend another 75.00 and take the 2 that come with the imac and replace all of them..

right?

right, and send me the two you take out


Actually, I'm not finding 4GBs to upgrade to 16 as a 4x4. Everyone wants to sell you 8GB DIMMS. hmm.

 

[BSoares]

So does anyone have a coupon code for Crucial?

Ebates has a link for 5% off and you get 6% cashback too. Also, you can order this kit instead of the one they show for iMac (same exact thing) for $4 less than the iMac suggested kit. CT2KIT102464BF160B

 

[Galatian]

-.-"

8 + 4 + 8 + 4 = 24.



8 + 4 in each channel will give you dual channel. 8 + 8 in one and 4 + 4 in another will give you async dual channel which is a very small performance loss. Honestly it doesn't matter but if you want to be 100% sure you don't lose out on any performance just put 8 + 4 in each channel. I don't know the DIMM assignments for the new iMac but it is not hard to figure out once you get it (you have 50% chance of getting it right lol).

Either you or me are misunderstanding dual channel: In layman's terms how I understood it, it is actually addressing 2 separate memory sticks parallel and therefore increasing throughput, which means two sticks that are supposed to run together in dual channel should be the same size. You can use different sizes but that is not recommended as it can decrease speed. So the bank should be equipped 8+8 and 4+4. I think we are both talking about the same thing just one of us has a problem with the nomenclature...

 

[lixuelai]

Either you or me are misunderstanding dual channel: In layman's terms how I understood it, it is actually addressing 2 separate memory sticks parallel and therefore increasing throughput, which means two sticks that are supposed to run together in dual channel should be the same size. You can use different sizes but that is not recommended as it can decrease speed. So the bank should be equipped 8+8 and 4+4. I think we are both talking about the same thing just one of us has a problem with the nomenclature...

The info I provided has been very clear and everyone else in this thread understood it perfectly fine. If you have issues with it then it is not my problem...

 

[bgsnmky]

right, and send me the two you take out :d


.

 

[ronm99]

I don't know for sure, but I believe that you just add the new memory to the two empty available slots, and everything should be okay.

You can verify by going to "About this Mac" --> More Info --> System report.

If you click on "memory", you can see what memory is installed in what slots. You want each bank to have matched RAM cards (size & ideally manufacturer as well).

 

[ctdonath]

After blowing some $2500 on new computer, and spending around $100 for filling the two empty RAM slots, seems a no-brainer to let a little more cash go (around 2% of total system cost) to just max it out entirely. Why stop at 24GB if you're already ordering & installing?

 

[mab75]

I don't know for sure, but I believe that you just add the new memory to the two empty available slots, and everything should be okay.

You can verify by going to "About this Mac" --> More Info --> System report.

If you click on "memory", you can see what memory is installed in what slots. You want each bank to have matched RAM cards (size & ideally manufacturer as well).

I just installed 2 x 8Gb in the free slots of my 27" iMac, se picture!

So this would be the "wrong" way??
http://tinypic.com/r/16biw42/6

 

[badman08]

You get 24GB for just 68,99€ (amazon.de)

Link please B-)

 

[medi.freak]

Link please B-)

looks like prices went up.... probably due to demand from the new iMacs?

They are now

roughly 100€


and

about 91€



After getting my mac I am not sure I need more than 8Gb for now anyway though. It is good enough for what I am doing with it. For now

 

[MathijsF]

Either you or me are misunderstanding dual channel: In layman's terms how I understood it, it is actually addressing 2 separate memory sticks parallel and therefore increasing throughput, which means two sticks that are supposed to run together in dual channel should be the same size. You can use different sizes but that is not recommended as it can decrease speed. So the bank should be equipped 8+8 and 4+4. I think we are both talking about the same thing just one of us has a problem with the nomenclature...

You are correct sir.

The info I provided has been very clear and everyone else in this thread understood it perfectly fine. If you have issues with it then it is not my problem...

It's not a personal attack, you are just wrong.

Memory in dual channel works in pairs. So if you have 4 slots you actually have 2 Channels. What you were suggesting is that 4 slots make up one channel. That is not the case.

Maybe you should read this section: http://en.wikipedia.org/wiki/Multi-channel_memory_architecture#Operation

My suggestion for the Thread Starter, this is perfectly possible but you have to run your memory in Channel A: 4-4 and Channel B: 8-8 or vice versa. As long as the identical memory banks are in the same channel you are good.

 

[2bcool2]

can someone whos researched tell us cheapest 2 x 8gb UK deal

can someone who has looked everywhere in uk for the best deal on 2 x 8gb sticks please give a link ...

is there any deals / codes / quidco ?

thnx

 

[roverma]

There is no performance hit for running 24GB of RAM if the RAM is installed properly. Ivy Bridge is dual channel so make sure you have 12GB installed on each channel.

Wrong, for correct dual channel operation you have to install 2x4 in one channel and the 2x8 in the other channel!

 

[nosnhojm]

Wrong, for correct dual channel operation you have to install 2x4 in one channel and the 2x8 in the other channel!

Some confusion may be due to terminology; channels, banks, slots, dimms, etc.

For dual channel / matched RAM to work properly, you want to install them in different banks, but same dimm. For example:

• Bank 0 / Dimm 0 - 4 GB
• Bank 1 / Dimm 0 - 4 GB
• Bank 0 / Dimm 1 - 8 GB
• Bank 1 / Dimm 1 - 8 GB

 

[roverma]

Some confusion may be due to terminology; channels, banks, slots, dimms, etc.

For dual channel / matched RAM to work properly, you want to install them in different banks, but same dimm. For example:

• Bank 0 / Dimm 0 - 4 GB
• Bank 1 / Dimm 0 - 4 GB
• Bank 0 / Dimm 1 - 8 GB
• Bank 1 / Dimm 1 - 8 GB

Not...., read this:
"If the motherboard has two pairs of differently colored DIMM sockets (the colors indicate which bank they belong to, bank 0 or bank 1), then one can place a matched pair of memory modules in bank 0, but a different-capacity pair of modules in bank 1, as long as they are of the same speed. Using this scheme, a pair of 1 GB memory modules in bank 0 and a pair of matched 512 MB modules in bank 1 would be acceptable for dual-channel operation."

So 2x4 in bank 0 and 2x8 in bank 1

 

[Bear]

I don't see why no one in this forum intends to add 2 x 8GB chips and keep using the 2 x 4GB chips that come with the iMac. Waste not want not... is there a problem with running 24 GB?

No problem at all and if you need more than 8GB and don't need to go all the way to 32GB it's a cost effective solution.

those of you pulling the original 8 should consider selling it cheap to someone here. with paypal or a similar service, you could make a safe transaction and not bother with the additional fees of ebay. The benefit over somewhere like Craigslist, your working with a fellow iMac owner

Or you should consider keeping the original memory while still under warranty/AppleCare. Under certain circumstances Apple will require the original ram for repairs. And requires it if they decide to replace the machine.

I would simply check with Apple on proper instillation. Might even be in the manual. it can't be that hard to figure out, as they will have installed the 2x4GB into slots to take advantage of the performance channels, leaving the two remaining for whatever you want to add.

Usually the 2 empty slots are the correct slots to use.

I came to ask this precise question. The consensus seems to be that, if you buy a 16GB kit (8x2) and put a stick in each empty slot, you'll be in sync and problem free. Right?

Yes.

After blowing some $2500 on new computer, and spending around $100 for filling the two empty RAM slots, seems a no-brainer to let a little more cash go (around 2% of total system cost) to just max it out entirely. Why stop at 24GB if you're already ordering & installing?

It depends on how much ram you really need. From my current usage on an 8GB iMac, I think I need about 10GB of ram, so going to 24 GB would be more than enough. Also, as I stated above you should keep the original ram and it's easiest to keep it in the iMac if you don't need more than 24GB of ram.

 

[cirus]

Not...., read this:
"If the motherboard has two pairs of differently colored DIMM sockets (the colors indicate which bank they belong to, bank 0 or bank 1), then one can place a matched pair of memory modules in bank 0, but a different-capacity pair of modules in bank 1, as long as they are of the same speed. Using this scheme, a pair of 1 GB memory modules in bank 0 and a pair of matched 512 MB modules in bank 1 would be acceptable for dual-channel operation."

So 2x4 in bank 0 and 2x8 in bank 1

Correct, Each channel should have two identical DIMMs in it.
The DIMMs in different channels can be different.

 

[roverma]

Correct, Each channel should have two identical DIMMs in it.
The DIMMs in different channels can be different.

So to make it completely clear

You must NOT put the ( newly acquired) 2x8 in the slots Apple left blank.
the modules have to be rearranged:
2x4 in one bank and the 2x8 in the other bank.

 

[nosnhojm]

Not...., read this:
"If the motherboard has two pairs of differently colored DIMM sockets (the colors indicate which bank they belong to, bank 0 or bank 1), then one can place a matched pair of memory modules in bank 0, but a different-capacity pair of modules in bank 1, as long as they are of the same speed. Using this scheme, a pair of 1 GB memory modules in bank 0 and a pair of matched 512 MB modules in bank 1 would be acceptable for dual-channel operation."

You should really provide the reference when you quote something. That looks to be from Wikipedia.

I'm going off of what System Profiler says. I believe the iMac comes pre-populated with two sticks of RAM, one in bank 0 and one in bank 1. Unless you believe that Apple didn't match these for dual channel?