Got 3 beeps on memory install until...

[eric.johnson]

If you have ever opened up the compartment on the back of an iMac you'll see that Apple install the memory with a slot gap between modules so naturally when I saw this I thought, ok, I am not going to change what apple have setup so I will just install my new ram modules in the remaining slots the second down and the fourth one. Then, when I turned on the computer I got 3 beeps and thought bugger what have I done. I kept trying to make sure the ram was seated correctly and it was and I was still getting the beeps. Then I tried changing the apple 'default' ram to go to the top two ram slots and then put the new ram on the bottom to and presto it booted up!!

I am curious. Why did this happen? Does this mean I am getting dual channel? Did this do this because I have different sized ram sticks?

Thanks!

 

[chabig]

You didn't specify which iMac you have so nobody can answer your question. Apple does publish instructions for adding iMac memory:

https://support.apple.com/en-us/HT201191

 

[eric.johnson]

You didn't specify which iMac you have so nobody can answer your question. Apple does publish instructions for adding iMac memory:

https://support.apple.com/en-us/HT201191

Whoops yes it is a late 2014 iMac. The model identifier is 15,1.

 

[chabig]

Memory for that machines doesn't need to be installed in pairs. The three beeps just means the RAM didn't pass a data integrity check. Reseating it is probably what fixed it for you, and it would have been ok in any configuration.

https://support.apple.com/en-us/HT202768

 

[eric.johnson]

That is interesting so if you are looking top down at the memory bay I have apples default ram slot 1,2 and the new ram slot 3,4. So you're saying that it doesn't matter that I changed the order of what apple had it as slot 1 and 3 for their default ram. I am just wanting it to be in dual channel for the most optimal performance. Thanks heaps!

 

[chabig]

I am pretty sure that if the memory needed to be added in pairs, Apple would have said so in the RAM installation instructions. Since it wasn't mentioned, there is no optimum configuration. I think all DDR3 SO-DIMMs are 64 bits wide, which is the same width as the processor data bus, so worrying about banks is a thing of the past.