3 DDR3 modules (2x4GB & 1x8GB) still dual channel - how?

[jrichrds]

I have an Intel B85 chipset with Core I5-4570, and stuck in a spare 1x8GB with my existing 2x4GB and it still runs as dual channel. And I'm just curious how it works? Is it asynchronous dual-channel? Are the 2x4GB running in dual channel independently from the 1x8GB in single channel? Or is the memory controller pooling the 2x4GB in Channel A as a single 8GB, and thus the 8GB in Channel A and 8GB in Channel B are in synchronous dual channel?

 

[ElFenix]

interleaving.

although, you've got it really unbalanced (assuming you didn't move any of the 4GB sticks and you had it in dual channel already). you should stick the 8GB on one channel and have the 2x4GB on the other channel. then it should be fully interleaved. right now, you've got 1 channel with 12GB on it and the other with 4GB on it. so, only the first 8GB of 16 total is interleaved and running in dual channel.

 

[jrichrds]

interleaving.

although, you've got it really unbalanced (assuming you didn't move any of the 4GB sticks and you had it in dual channel already). you should stick the 8GB on one channel and have the 2x4GB on the other channel. then it should be fully interleaved. right now, you've got 1 channel with 12GB on it and the other with 4GB on it. so, only the first 8GB of 16 total is interleaved and running in dual channel.

I had the 2x4GB in Channel A black-colored slots, which was reported running in dual channel by CPU-Z. Then i put an 8GB in one of the Channel B white-colored slots. I didn't move either of the 4GB modules. I assume this is the right way to do it, as now each Channel has 8GB of memory total?

 

[ElFenix]

no, if it was running in dual channel already then you had 4GB per channel to begin with and then added 8GB to one of the channels. typically slots 1 and 2 are on one channel, and 3 and 4 are on another, so if you use 1 and 3, or 2 and 4, you get dual channel. they color those pairs so that you'll have a visual indication of which slots to use to run in dual channel.

so, to have full interleaving and run dual channel all the way up to 16GB, you'd need to put the 4GB sticks in both slot 1 and 2, or slot 3 and 4, with the 8GB stick in one of the remaining two slots.

edit: basically, if you want to check, take out the 8GB stick, move one of the 4GB sticks, boot up without the 8GB stick. you should now be running in single channel with 8GB. check that with CPU-Z. then add in the 8GB stick.

 

[LTC8K6]

As far as I know, Intel chipsets have been able to mix and match and still run dual channel for a while now. Flex mode allows dual channel with mismatched modules.

https://www.intel.com/content/www/us/en/support/articles/000005657/boards-and-kits.html

 

[jrichrds]

no, if it was running in dual channel already then you had 4GB per channel to begin with and then added 8GB to one of the channels. typically slots 1 and 2 are on one channel, and 3 and 4 are on another, so if you use 1 and 3, or 2 and 4, you get dual channel. they color those pairs so that you'll have a visual indication of which slots to use to run in dual channel.

so, to have full interleaving and run dual channel all the way up to 16GB, you'd need to put the 4GB sticks in both slot 1 and 2, or slot 3 and 4, with the 8GB stick in one of the remaining two slots.

edit: basically, if you want to check, take out the 8GB stick, move one of the 4GB sticks, boot up without the 8GB stick. you should now be running in single channel with 8GB. check that with CPU-Z. then add in the 8GB stick.

Thank you! That makes sense. I'll swap the 8GB and one of the 4GB modules.

 

[jrichrds]

no, if it was running in dual channel already then you had 4GB per channel to begin with and then added 8GB to one of the channels. typically slots 1 and 2 are on one channel, and 3 and 4 are on another, so if you use 1 and 3, or 2 and 4, you get dual channel. they color those pairs so that you'll have a visual indication of which slots to use to run in dual channel.

so, to have full interleaving and run dual channel all the way up to 16GB, you'd need to put the 4GB sticks in both slot 1 and 2, or slot 3 and 4, with the 8GB stick in one of the remaining two slots.

edit: basically, if you want to check, take out the 8GB stick, move one of the 4GB sticks, boot up without the 8GB stick. you should now be running in single channel with 8GB. check that with CPU-Z. then add in the 8GB stick.

Does this look right?
The 8GB is in DDR3_2 and the 2x4GB are in the DDR3_1 and DDR3_3 slots.
I'm able to run 1600Mhz CL9 now, whereas before I had to do CL10.