2009 21.5" iMac, max RAM states 16GB, can I use 2x 8 GB sticks? or does it have to be 4 x 4GB?

[aqe]

I have this iMac here: https://everymac.com/systems/apple/...uo-3.06-21-inch-aluminum-late-2009-specs.html

I would like to upgrade the RAM, but first I have some questions:

1) The maximum amount says 16GB, but is that true? I read some iMacs can hold more RAM but Apple never bothered to write that in the specs, so if I put in lets say 20GB of RAM total, will it still work? or will it not boot up? Or will it boot up and I only get to use 16GB out of the 20GB?

2) I currently have 2 x2gb = 4gb, but there are 4 RAM slots, do I have to get 4x 4gb of RAM? or Can i use 2 x 8GB of RAM and leave the other 2 slots empty (or leave in the 2x2gb and have 20GB total)?

 

[nambuccaheadsau]

Go with 4 x 4GB modules as 16GB is the maximum according to Mactracker. 4GB modules would have been the maximum the iMac would take at the time of manufacture.

 

[aqe]

So are you saying an 8GB module (or 2) won't work? What would happen if i installed 2x 8GB modules? I would prefer to have 2x 8GB over 4x4GB because the 8GB modules would be more likely to reused in the future (in another computer) due to the larger capacity.

 

[retta283]

16GB is the board limit on the 2009 21.5, the 27 can do 32GB.

4x4 would be the surefire way, I wouldn't know about 2x8. I don't see why it would have an issue if the RAM is the correct spec. If you buy from a place that allows returns you can go for 2x8GB and if that fails, return and swap for 4x4.

 

[MacUser2525]

16GB is the board limit on the 2009 21.5, the 27 can do 32GB.

4x4 would be the surefire way, I wouldn't know about 2x8. I don't see why it would have an issue if the RAM is the correct spec. If you buy from a place that allows returns you can go for 2x8GB and if that fails, return and swap for 4x4.

4x4 is the configuration that works, it is the way computers are when the manufacturer pulls that scummy move. And is mentioned in the linked specification page as only supported configuration. They artificially limited the options in the firmware to prevent it from working like you would think it should.

 

[retta283]

4x4 is the configuration that works, it is the way computers are when the manufacturer pulls that scummy move. And is mentioned in the linked specification page as only supported configuration. They artificially limited the options in the firmware to prevent it from working like you would think it should.

You've sparked some memories with this post. I had a similar story happen with a couple of Windows boxes back in the 2000 days. I had to use a specific combination of RAM for it to function.

 

[aqe]

If I get the 4x4GB, what speed should I get? The iMac calls for DDR3 1066MHz PC3-8500 RAM, but I know that faster RAM can work as well, it will just run at the lower speed. But I want to get even faster RAM in case I reuse it in another computer in the future.

Should I get 1066mhz (default)? or 1333mhz or 1600mhz? If I get 1600mhz RAM it will still work in this iMac right? It will just run at 1066mhz, it that right? (which is fine by me).

 

[nambuccaheadsau]

Buy the memory you quoted as faster memory cannot perform any faster than permitted by the system bus speed.

 

[aqe]

Buy the memory you quoted as faster memory cannot perform any faster than permitted by the system bus speed.

I know, but will 1666mhz RAM work in a 1066mhz RAM slot running at 1066mhz (I don't care if it doesn't run at the 1666mhz speed though, I want to get the 1666mhz for the future)? What are the specs to check?

 

[MacUser2525]

You've sparked some memories with this post. I had a similar story happen with a couple of Windows boxes back in the 2000 days. I had to use a specific combination of RAM for it to function.

Indeed the part I deleted and did not post said. When I first started with these things there was no guarantee an identical set would work together, without you preforming some Voodoo, like dancing naked in the full moon light while sacrificing a chicken to the ram Gods...
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I know, but will 1666mhz RAM work in a 1066mhz RAM slot running at 1066mhz (I don't care if it doesn't run at the 1666mhz speed though, I want to get the 1666mhz for the future)? What are the specs to check?

Just make sure they are identical modules running at least the speed supported by your machine. It makes little sense to get the highest 1600 ones as I do not think apple ever supported that speed only the 1333mhz. So unless you plan on putting it in a windows laptop it will never be used at its rated speed.

 

[nambuccaheadsau]

1600MHz memory was used on late 2013 27"models for sure. I guess if youn upgrade it will be later than that model.

 

[aqe]

Just to update this thread, I pulled an old stick of DDR3 4GB 667mhz RAM out of an old laptop and added to the iMac, so currenty running 2 x2GB + 1 x 4GB = 8 GB total in the iMac.