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Issue when installing memory 2011 iMac

J

jduffy

macrumors member
Original poster
May 1, 2011
42
0
Well this is interesting. I received the two 4GB memory modules from Crucial today to install in 2011 21.5 iMac.

I put both modules in the empty slots and what do you know, it won't start.

So I remove the modules. Put in just the original Apple memory modules and it starts.

Shut it down and put in one memory module. It starts and shows 8GBs of memory.

Shut it down again. Take out one of the Apple 2GB memory modules and replace with remaining Crucial 4GB memory module. System starts and tells me I now have 10GBs of memory. O.K., maybe a bad memory slot. Shut it down again. Put in the 2GB Apple memory module into the remaining slot, it turns on and boots fine and now shows 12GBs of memory.

But the modules are in a 2GB 4GB on the first two slots and 4GB and 2GB in the secondary slots.

It works this way. Seems the iMac does not have any issues so far, but seems strange it only works this way. Anyone see any issues with leaving them as is? I have started a bunch of programs at the same time, VMware Fusion running Windows7, iMovie, Aperture, Open Office, and Safari and all seems to work well. Should I just leave well enough alone?

Thanks,

Duffy
 
jduffy said:
Well this is interesting. I received the two 4GB memory modules from Crucial today to install in 2011 21.5 iMac.

I put both modules in the empty slots and what do you know, it won't start.

So I remove the modules. Put in just the original Apple memory modules and it starts.

Shut it down and put in one memory module. It starts and shows 8GBs of memory.

Shut it down again. Take out one of the Apple 2GB memory modules and replace with remaining Crucial 4GB memory module. System starts and tells me I now have 10GBs of memory. O.K., maybe a bad memory slot. Shut it down again. Put in the 2GB Apple memory module into the remaining slot, it turns on and boots fine and now shows 12GBs of memory.

But the modules are in a 2GB 4GB on the first two slots and 4GB and 2GB in the secondary slots.

It works this way. Seems the iMac does not have any issues so far, but seems strange it only works this way. Anyone see any issues with leaving them as is? I have started a bunch of programs at the same time, VMware Fusion running Windows7, iMovie, Aperture, Open Office, and Safari and all seems to work well. Should I just leave well enough alone?

Thanks,

Duffy
Click to expand...

RAM channels should be matched accordingly, so yes, it doesn't surprise me that it only works on one configuration.

Usually it's channel 1+3 must be identical, with 2+4, etc. It depends on the motherboard and who knows how the iMac's does it.
 
thats strange :D how much did u buy the ram for? and why did u choose crucial over say Kingston?
 
Zen0Jin said:
RAM channels should be matched accordingly, so yes, it doesn't surprise me that it only works on one configuration.

Usually it's channel 1+3 must be identical, with 2+4, etc. It depends on the motherboard and who knows how the iMac's does it.
Click to expand...

I thought like you, but as it turns out, the memory modules are installed in the following manner:

BANK0/DIMM0 2GB
BANK1/DIMM0 4GB
BANK0/DIMM1 4GB
BANK1/DIMM1 2GB

Nothing seems to be logically matched....but it works this way. Go figure. I think I'll send a note to Crucial to see if there is some explanation.

Duffy
 
lamonsas said:
thats strange :D how much did u buy the ram for? and why did u choose crucial over say Kingston?
Click to expand...

Just under $90 for the 8GBs. Crucial has always worked perfect for me, and I guess it is working, just not the way I thought it would.

Duffy
 
will sucscruibe this thread and keep you posted when i recieve both my new iMac and my 2x4GB memory wich i'll buy... not @ apple...
interested if any other people make the same experience, i'll keep you posted
 
do u notice any speed improvment over the 4GB stock ram?

im going to get my 2011 iMac tomorrow too and im thinking about upgrading the ram to 12GB too.
 
jduffy said:
Just under $90 for the 8GBs. Crucial has always worked perfect for me, and I guess it is working, just not the way I thought it would.

Duffy
Click to expand...

can u post a link from amazon for the crucial ram that u bought?
 
lamonsas said:
do u notice any speed improvment over the 4GB stock ram?

im going to get my 2011 iMac tomorrow too and im thinking about upgrading the ram to 12GB too.
Click to expand...

Yes, I increased the amount of memory available for the Windows Virtual Machines and the start up screams. All programs are starting faster and I can run a bunch at the same time and the memory usage so far has not exceeded 9GBs when I have all sorts of stuff up and running.

With the 4GBs of stock memory, it used to be at 100% memory usage most of the time.

Duffy
 
wow it sounds like ill have to upgrade my Ram if the 4GB ram was full at 100 percent.
 
Hi,

I had a similar problem yesterday:

BANK0/DIMM0 2GB
BANK1/DIMM0 4GB
BANK0/DIMM1 2GB
BANK1/DIMM1 4GB

...showed up as 6GB RAM when I powered up the iMac. I changed it to:

BANK0/DIMM0 4GB
BANK1/DIMM0 2GB
BANK0/DIMM1 4GB
BANK1/DIMM1 2GB

...and it now works a treat, showing 12GB.
 
Robert Grant said:
Hi,

I had a similar problem yesterday:

BANK0/DIMM0 2GB
BANK1/DIMM0 4GB
BANK0/DIMM1 2GB
BANK1/DIMM1 4GB

...showed up as 6GB RAM when I powered up the iMac. I changed it to:

BANK0/DIMM0 4GB
BANK1/DIMM0 2GB
BANK0/DIMM1 4GB
BANK1/DIMM1 2GB

...and it now works a treat, showing 12GB.
Click to expand...

Robert, who is the manufacturer of the new memory modules that you added?
 
Just picked up some Corsair RAM and installed it, worked right away:

BANK0/DIMM0 2GB
BANK1/DIMM0 2GB
BANK0/DIMM1 4GB
BANK1/DIMM1 4GB

Is dual channel based on the DIMM slots or the BANK?
 
Well the system locked up tonight (kernel panic?) so I removed the previously offending module, put the second original Apple 2GB module back into its original slot, rebooted and it seems to be working well again. We'll see over time. In any case, I requested and received an RMA from Crucial to send this module back for replacement. In the meantime, at least I have 8GBs of memory and that seems to be plenty for now. So no biggie having to wait for the replacement 4GB module. Still a fan of Crucial.....that is as long as the replacement module works without issue :)

Duffy
 
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