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Is it OK to use 1 x 8GB RAM stick in a Dual Channel (4 slots) ?

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pmap93

Registered
Joined
Jun 30, 2014
Location
Dubai, United Arab Emirates
Hello!

I'm planning my next build :)

I'm wondering if it is safe to use ONE 8GB stick of RAM to achieve 8GB in a Dual Channel slot?

Or it is completely necessary to use a pair like 2 x 4GB ? :eh?:

Thanks in advance :)
 

Mr.Scott

Beamed Me Up!
Joined
Jun 9, 2013
One stick will not give you dual channel. It works in pairs.
A single 8 gig stick in any slot will give you 8 gig in single channel.
 

caddi daddi

Godzilla to ant hills
Joined
Jan 10, 2012
it will work, but in single channel mode, you will get less out of it than you would with 2x4 gig sticks.
 

ATMINSIDE

Sim Racing Aficionado Co-Owner
Joined
Jun 28, 2012
Its safe, the computer will run, but it will have half the bandwidth of a 2x4GB setup.

You WILL notice the difference.
 

GearingMass

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Jun 24, 2014
Location
TX/CO
Crap I was about to make the same mistake in my new build. Looks like I'll be running by micro center today. :-/
 

Silver_Pharaoh

Likes the big ones n00b Member
Joined
Sep 7, 2013
Question: Would it be better to run 4x2Gb sticks instead of 2x4Gb?

Quad-channel? :shrug:
(Sorry for jacking)
 

GearingMass

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Location
TX/CO
From my very new understanding, 4x2GB would only be better if your motherboard supported quad channel. If it's only duel channel, I would think it better to stick with 2x4GB and leave the other two slots open for potential future expansion.
 

Woomack

Benching Team Leader
Joined
Jan 2, 2005
Most new popular IC perform like:
single 4GB < 8GB
dual 2x4 or 4x4GB < 2x8 or 4x8GB
quad 4x4 or 8x4GB < 4x8 or 8x8GB

Older 4GB modules were double sided and 4GB = 8GB in general performance but you won't find them in any new kits.

Also 3 modules are usually working as dual channel and have the same performance as 2 or 4 modules on a dual channel platforms.
 

EarthDog

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Buckeyes!
Also 3 modules are usually working as dual channel and have the same performance as 2 or 4 modules on a dual channel platforms.
Doesn't the 3rd stick run in single channel?
 

Woomack

Benching Team Leader
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Jan 2, 2005
At least on Z77, Z87, Z97 and A88X I was running 3 sticks in dual channel without performance drops. The same 4 sticks on X58 were working as triple channel when placed in correct slots.
 

ATMINSIDE

Sim Racing Aficionado Co-Owner
Joined
Jun 28, 2012
At least on Z77, Z87, Z97 and A88X I was running 3 sticks in dual channel without performance drops. The same 4 sticks on X58 were working as triple channel when placed in correct slots.

I believe EarthDog is correct here.
The OS will fill the dual channel capacity first, then fill the single channel.

So, if you had 2x4GB and 1x8GB you would have to use >8GB to see a performance drop.
 

Woomack

Benching Team Leader
Joined
Jan 2, 2005
I believe EarthDog is correct here.
The OS will fill the dual channel capacity first, then fill the single channel.

How can it fill dual channel and then single channel when there is one dual channel and all RAM is shared, not split ?

So, if you had 2x4GB and 1x8GB you would have to use >8GB to see a performance drop.

I'm not sure what are you talking about here.
 

EarthDog

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At least on Z77, Z87, Z97 and A88X I was running 3 sticks in dual channel without performance drops. The same 4 sticks on X58 were working as triple channel when placed in correct slots.
X58 is a bit different in that it could do that (had more flexibility on channeling). I wasn't sure the 'mainstream' platform could allocate 3 sticks in a dual channel configuration. I was thinking it would run the dual ch sticks as dual and the single as single...

Let me look up a couple of manuals and see what they say. I recall seeing one that showed with three, 2 were in dual channel while the 3rd was in single...(though I could be off - hang tight)........

I'm not sure what are you talking about here.
He is saying that the 2x4GB is dual, while the 1x8GB is single. It will use the 2x4GB dual capacity first, but after that 8GB it will be single channel...

Im thinking of it this way... if dual channel requires two slots to be populated, how can 3 also be dual as it does not have the 2nd stick to run dual channel?
 
Last edited:

Woomack

Benching Team Leader
Joined
Jan 2, 2005
Last time when I was using 3 sticks in dual channel was last week. My daily PC is now based on ASRock A88X Extreme6 and I was using 3x 4GB Avexir/Elpida based single sided modules. Every soft saw dual channel and performance was the same as on 2 modules. I sold all these memory sticks last friday.

Most manuals are saying that 3 sticks = single channel, 2 or 4 are dual channel but in real it works also with 3 just sometimes depends from a board or BIOS.
 

EarthDog

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Most manuals are saying that 3 sticks = single channel, 2 or 4 are dual channel but in real it works also with 3 just sometimes depends from a board or BIOS
That is what I am saying, we really do not have software that shows what dual/single channel for each DIMM. I believe the 2x whatever is dual channel but the single stick is single in a 3 stick setup. Performance would be the same unless you got past the dual channel capacity (as ATM said) is what I also think happens.

Is there any way to conclusively find out via software for each DIMM?

I suppose I can reach out to MSI and see what they say about it. :)
 

Woomack

Benching Team Leader
Joined
Jan 2, 2005
I think it's not about modules but about memory controller. If it fills enough banks to work at higher bus bandwidth then it's activating dual channel. Support for that has to be made in BIOS and I think that manufacturers are protecting themselves from incompatibility issues saying that 3 modules will work only in single channel. The same was on earlier boards regardless of used chipset.
Soft is now showing info about single modules but about whole memory controller bandwidth as all RAM is shared.
Nforce2 was working in dual channel on 3 modules and these boards had 3 slots. All newer chipsets are officially supporting 2/4 or more modules in dual channel. Manufacturers are not even testing compatibility with 3 modules ( except X58/server boards ).
 

EarthDog

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I also agree it is how the memory controller deals with the number of sticks, no doubt. I still think with 3 sticks 2 are dual, the third is single though as the third stick does not have a 'partner' for dual channel.

According to the ASUS manual for z87 Sabertooth, when running mismatched capacity DIMMs, it will allocate the lowest common denominator (say its a 4GB stick and 8GB stick) in dual channel (so 8GB total) and the remaining 4GB in single channel. That tells me the controller has the flexibility to run single and dual channel at the same time. I am aware we are not talking mismatched capacity, but wanted to share that as an example of the flexibility of the IMC to run both dual and single at once. I believe intel calls this "Flex mode".

ASUS Z87 Sabertooth manual - See page 1-12, first paragraph




EDIT: Here we go...http://www.intel.com/support/motherboards/desktop/sb/cs-011965.htm#flex

Rules to enable dual-channel mode

To achieve dual-channel mode, the following conditions must be met:

Same memory size. Examples: 1 GB, 2 GB, 4 GB.
Matched DIMM configuration in each channel
Matched in symmetrical memory slots