Can I mix 4x8gb and 2x4gb on an X58 in triple channel?

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RyanLucier

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I have 4x8gb and 3x4gb, all of which is 1600mhz ddr3. Can I mix 4x8gb and 2x4gb on an X58 in triple channel? I'm guessing my best bet is:

3x8gb
3x4gb
total of 36gb of ram

Or could I use:
4x8gb
2x4gb
total of 40gb of ram

any suggestions? I've done some googling but haven't found much, conflicting reports that if I populate all 6 dimm's it will stay at triple channel even if different memory sizes, and some saying that it won't, but will in fact operate in dual channel etc...

Any advice is appreciated!
 
First of all, which CPU are you using? And how old is it, and which stepping? You see, the LGA 1366 CPU's IMC is officially limited to 2GB per rank (or 4GB per stick). And if you have a very early CPU, 8GB sticks may not even work at all with such a CPU.
 
Hi, I have an i7 920 and a asus p6t deluxe (first revision).

It does work with 8gb though, as i'm currently using 3x8gb without issue, so I'm lucky I suppose?

Thanks!
 
it will operate dual channel as it is odd sized, unless they have very fancy memory controller that I do not know about.

Channels a-b-c have to be populated equally for best performance and for proper operation
so say you had 3 sticks all the same size in a-b-c then it would be tru ti-channel
but if you had 1 size in channel a-b but another in channel c then it has no choice but to operate in dual channel on a-b and single on channel c, at least this is my understanding.

Like with the new chips that use dual channel, they take a performance hit if odd size is used in channel A and a different size in channel b, but it will operate in dual channel, so I would assume it should as well in tri-channel, but what may happen, possibly, is that a-b will do dual and c will operate single channel, so the only thing you get is capacity, not outright bandwidth, which is the whole point of going tri-channel to begin with for the most part. Better to have dual channel with matched capacity then to have a mix and match set of different capacities, I am sure beyond the performance hit that it would likely incur(if it does work) it would not operate as well as it can.

Memory controller/chipset can only do so much, and you`re asking for possible issues attempting to do this. Or I guess the better way to look at it, if a-b-c all are same cap and speed, then cpu can possibly use them as 1 mass unit shifting what it needs where it needs to, but if different size on 1 channel then another, then its out of sequence, and probably will not net the best performance, and could have usage errors?(Im just throwing a stick here :p)
 
In this case, then, using mixed-sized sticks of RAM will officially put the IMC into an "imbalanced" Flex memory controller mode, and it will depend on where you install those sticks. If you put three 8GB sticks and three 4GB sticks, then which slots that the memory will be placed will determine which mode the IMC will run in: For example, putting the three 8GB sticks in the first set of slots indicated for triple-channel and putting the three 4GB sticks in the other tripled set of slots will still give you full triple channel. However, if you put the sticks in an "irregular" order, then the memory controller channel with the least amount of RAM installed will determine triple-channel mapping (for example, of the 36GB total, only the first 24GB will run in triple channel and the remaining 12GB will run in single channel).

If on the other hand you put in four 8GB sticks and two 4GB sticks, then you will have 40GB total - and not all of that will run in triple channel. In fact, some of it will run in single channel. More than likely, you will have 36GB running in triple channel and 4GB running in single channel.
 
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Thanks for the great advice!

Sounds like best bet is 3x8gb and 3x4gb. For a total of 36gb memory, running triple channel

Agree / Disagree???

Thanks guys
 
SlayVus said:
ASUS Says that Mobo can only support a max of 6 DIMMs up to 24GB max.
Click to expand...

That is Intel's official limit on the entire LGA 1366/X58 platform combo (with unbuffered DIMMs). 8GB DIMMs may work; however, there is no guarantee that they will.
 
Just FYI, did some digging, folks did run 48gb of ram on this particular mobo. Thats not my intention, but just in case anyone else comes across this thread and wonders, it can be done

think im gonna try 3x8 and 3x4 tomorrow... *crosses fingers* :)
 
Is there a specific reason you need to run 36GB of ram? If you end up losing some tripple channel support the real world performance you experience may be slower regardless of the increase in ram.

Just food for thought.
 
You want the same total amount of RAM in each bank if possible, but other than that you can mix stick sizes. 2-3 sticks per bank will probably have to run with slower timings than 1 stick per bank.
 
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Good thread, yeah 3x8 + 3x4 is your best bet if you really need that much RAM. Pretty sure people are needing more memory controller voltage and still not achieving their old clocks when maxing x58 RAM...ymmv.
 
If the 8GB sticks work, I'd probably just run the 4x8GB sticks in asynchronous triple channel, ditch the 4GB sticks completely.
 
AIUI what matters with intel processors is the total amount of memory on each channel.

My understanding is if you put 1x4GB and 1x8GB on two channels and 2x8GB on the remaining channel you will have 36GB running triple channel and 4GB running single channel.

Which means an app that happens to end up in that last 4GB will get worse memory performance than one elsewhere in memory. On the other hand more memory means more space to cache stuff from disk.

So the question is which matters more to you? consistent performance or greater total available ram?
 
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