As was stated previously, Macs are highly picky about RAM.
Laptop and desktop RAM are different and different specs.
There is no mixing of RAM types, either.
If the RAM is not of the proper specs for the Mac, in question, it wil not work and/possibly do other damage, as well.
Currently Being ModeratedSep 7, 2012 11:47 AM (in response to Jeff Mark)
So I got one of those 6GB packages from AWC (Crucial didn't respond to my email inquiry, and they don't seem to have an equivalent product); $120.
The difference has been somewhere between significant and dramatic. It's only an increase of 2GB (although that is 50%) but things are much peppier. I'd had a problem with apps (e.g., Numbers) taking forever to "wake up" after system sleep; that seems much improved. I'd also been having Safari stall out way too frequently for my comfort, that's improved as well. I'm even seeing better performance of Windows using Parallels 8.
Also, I was doing some follow-up, and I think the leftover DIMMs from this will in fact work in my MacBook, but I haven't tried yet.
This looks like it's working out.
And, of course, C|NET this morning reported rumors of new iMacs...
Currently Being ModeratedSep 7, 2012 12:43 PM (in response to MichelPM)
There are really no exception to your statement ?
I have done a lot of check with OWC and Crucial and compared with the system report of my iMac 27 i7 MID 2011 and my MBP Early 2011 i7.
Both can install DDR3 1333 204PIN.
Sometimes they are called DIMM0 or SO-DIMM.
Am I missing something ?
Even from the pictures on OWC they look the same.
My target whould be buy 2x8GB to install in the MBP and the 2x4GB removed will be installed in the 2 free slots of the iMac which already has 2x4GB.
Will you pls help me to understand ?
I could do one practica test myself removing the 2 from MBP and installing them in the iMAC: if they are "mechanical compatible" that is enter the slot, may I proceed ?
Thanks for your time.
Currently Being ModeratedJan 4, 2013 12:34 PM (in response to Jeff Mark)
Well, although late to this, I have just replaced a 2GB with 4GB of Crucial RAM and no problems. iMAC now running much fast. Next step is to wait for 512GB SSD to drop to a favourable price and swap out the 320GB HDD.
Currently Being ModeratedFeb 14, 2013 11:09 AM (in response to wislonp)
wislonp - interesting - this is my issue also. I have a Mid 2007 2.4. Intel Dual Core which is struggling at 4GB to cope with my music composition software and I've also run out of hard disk. I'm wondering whether to upgrade to 6GB RAM and get the 512SSD or just accept that I need a new machine - there is however a difference of well over £2000 between these options and it's not worh investing in the SSD if 6GB isn't good enough.
Currently Being ModeratedFeb 14, 2013 11:43 AM (in response to WALTER-MILANO-ITALY)
If all the RAM is 204 pin SO-DIMM, then it should fit in the slots without damaging anything. But the responses back to the OP's multiple questions cover all sorts of issues, from pair matching, to MMU supported address space, to system bus speeds.
You can put 800MHz RAM into a 667MHz bus and it may work (at the slower speed). You can put 8GB of RAM in a system that is only capable of addressing 6GB and it may work (or just fail outright). You can mix RAM from different manufacturers and it may work (and more than likely be OK).
When you start doing a bunch of things that each may work at the same time, the combination is often almost certain not to work.
Sometimes buying exactly what you need, all new, is just cheaper and easier in the long run.
Currently Being ModeratedFeb 14, 2013 8:48 PM (in response to Raystrack)
I Think you'll find that installing that extra two GBs of RAM for a total of 6 GBs, will make more of a speed improvement than you think.
If you are running low on hard drive space, it maybe time for an external FireWire 400/800 hard drive or an expensive large capacity SSD.
Also, here are some tips to relieve some of your hard drive space.
Have you emptied your iMac's Trash icon in the Dock?
If you use iPhoto, iPhoto has its own trash that needs to be emptied, also.
If you use Apple Mail app, Apple Mail also has its own trash area that needs to be emptied, too!
Other things you can do to gain space.
Delete any old or no longer needed emails and/or archive older emails you want to save.
Look through your Documents folder and delete any type of old useless type files like "Read Me" type files.
Again, archive or delete any old documents you no longer use or immediately need.
Uninstall apps that you no longer use. If the app has a dedicated uninstaller, use it to completely uninstall the app. If the app has no uninstaller, then just drag it to the OS X Trash icon and empty the Trash.
Download an app called OnyX for your version of OS X.
When you install and launch it, let it do its thing initially, then go to the cleaning and maintenance tabs and run all of the processes in the tabs. Let OnyX clean out all web browser cache files, web browser histories, system cache files, delete old error log files.
Typically, iTunes and iPhoto libraries are the biggest users of HD space.
You may have to Purchase an external FireWire or Thunderbolt hard drive to move these files/data off of your internal drive to the external hard drive and deleted off of the internal hard drive.
If you have any other large folders of personal data or projects, these should be moved, also, to the external hard drive and then either archived to disc and/or deleted off your internal hard drive.
Currently Being ModeratedFeb 14, 2013 8:57 PM (in response to WALTER-MILANO-ITALY)
If there is the tiniest of timing variation in the RAM you have or want to use, it either will not be stable or it simply will not work in your iMac. Period.
Notebook is Notebook RAM.
Desktop RAM is Desktop RAM. They are different profiles and can be timed differently.
Just purchase the 6 GBs kit as everyone else has done.
Install it into your iMac!
It'll just work. No issues! No doubts!
You can't tell how RAM is made or configured simply by looking at it!
Both Crucial memory and OWC have the correct and reliable RAM for your iMac model.
Both these companies have proven, reliable Mac RAM that work for the models they supply RAM for.
Currently Being ModeratedFeb 15, 2013 12:22 PM (in response to MichelPM)
Thanks for the advice. I have ordered a compatible 4GB chip from Crucial UK and will report back when it's fitted. I may have to order a replacement 2GB chip for the other slot if they need to be a complete match but Crucial didn't think it would be necessary (I had upgraded to a third party set of 2 x 2GBs a couple of years back).
I have three external 7200rpm drives but I have found the Firewire 800 slot to be unreliable when I have a sound interface permanently connected to the F400 slot as well; so they're on USB2 . I am used to clearing as much room as I can on the internal drive, but will try Onyx, thanks.
Currently Being ModeratedFeb 17, 2013 4:22 AM (in response to Raystrack)
I have ordered a compatible 4GB chip from Crucial UK and will report back when it's fitted.
I fitted one Crucial 4GB chip this morning alongside the existing 2GB from Buffalo and it works fine. The Onyx program is good if a little scary - I haven't let it do it's stuff on the Library and System drives yet as that's where my music engines are installed and they warn about installing any personal stuff there as it's likely to get erased. I'm not sure if these non-Apple products (which install themselves in those drives) would be treated as 'personal data' or not but I'm not risking it.