Dual + single channel memory?

[sarnak417]

Is it possible to use 2x4gb + 1x8gb ram sticks if they are all of the same serie? Would it be considerably different from using 4x4 or 2x8 sticks (faster or slower)?

I need to upgrade memories on my PC, but I am not sure to be able to put the 4th stick in place (cpu cooler might be too big) so im trying different ways to get the most out of 3 slots.

CPU: FX8350
MOBO: Gigabyte 990xa-ud3

 

[sna]

Is it possible to use 2x4gb + 1x8gb ram sticks if they are all of the same serie? Would it be considerably different from using 4x4 or 2x8 sticks (faster or slower)?

I need to upgrade memories on my PC, but I am not sure to be able to put the 4th stick in place (cpu cooler might be too big) so im trying different ways to get the most out of 3 slots.

CPU: FX8350
MOBO: Gigabyte 990xa-ud3

get low profile memory it will fit.

for dual channel mode you should add memory in pairs.

example of low profile memory

http://www.amazon.com/Crucial-Ballistix-DDR3-1600-BLS2K8G3D1609ES2LX0-BLS2C8G3D1609ES2LX0/dp/B00A14ZT8I/ref=sr_1_2?ie=UTF8&qid=1441523698&sr=8-2&keywords=Crucial+Ballistix+Sports+VLP

http://www.amazon.com/Crucial-Ballistix-DDR3-1600-BLS2K4G3D1609ES2LX0-BLS2C4G3D1609ES2LX0/dp/B00A14ZT6U/ref=sr_1_3?ie=UTF8&qid=1441523698&sr=8-3&keywords=Crucial+Ballistix+Sports+VLP

http://www.amazon.com/Crucial-Ballistix-DDR3-1600-BLT2K8G3D1608ET3LX0-BLT2C8G3D1608ET3LX0/dp/B00A14ZTRO

 

[Vic 40]

for dual channel mode you should add memory in pairs.

Not necessarily,with 2x4gb in one channel and 1x8gb in the other would that give dualchannel too.

I do agree on the low profile suggestion though.

Make sure it's the same make,model and speed,even then there's the possibility that it won't work well together.A nice artikel about ram to read with thanks to Tradesman1,
http://www.tomshardware.com/reviews/ddr-dram-myths,4155.html#p4

 

[sna]

for dual channel mode you should add memory in pairs.

Not necessarily,with 2x4gb in one channel and 1x8gb in the other would that give dualchannel too.

not if all memory is used ... will not be full dual channel above 8G usage

 

[Vic 40]

And why not?

 

[sna]

And why not?

how do you increase the bandwidth using dual channel then ? you need same capacity wired in dual channel mode to fill that memory ...

here read this

http://www.hardwaresecrets.com/everything-you-need-to-know-about-the-dual-triple-and-quad-channel-memory-architectures/3/


if he uses 2x4 and 1x8

the 2x4 will be dual while the 1x8 will be single , so once he is using more than 8G (2x4 filled) he will be using single channel again to fill the other 1x8G

 

[Tradesman1]

And why not?

how do you increase the bandwidth using dual channel then ? you need same capacity wired in dual channel mode to fill that memory ...

here read this

http://www.hardwaresecrets.com/everything-you-need-to-know-about-the-dual-triple-and-quad-channel-memory-architectures/3/


if he uses 2x4 and 1x8

the 2x4 will be dual while the 1x8 will be single , so once he is using more than 8G (2x4 filled) he will be using single channel again to fill the other 1x8G

___________________

While the article is correct as to older AMD mobos, this has long been a myth for newer mobos, Intel brought out what they call Flex mode years and years ago. AMD has taken the same approach, though they don't want to call it Flex as then they would have to pay Intel to use the term. Modern mobos, even many AMD mobos going back to the time of that article allow for the BIOS to simply look at the amount of memory in each channel (say 8GB in each channel (be it a single 8GB stick or 2x4GB in the 2 slots for the given channel ) and to use all 16GB in dual channel, also if Channel A has 8GB and channel B only 4GB then you would have 8GB in dual and the odd 4GB from the 8GB stick in single channel mode. More in my FAQs article (item 7) here:

http://www.tomshardware.com/answers/id-2741495/ddr3-faqs-fiction.html

Though there are no guarantees in mixing sticks from packages, which is covered in item 2 of the Fiction side of the article

 

[sna]

And why not?

how do you increase the bandwidth using dual channel then ? you need same capacity wired in dual channel mode to fill that memory ...

here read this

http://www.hardwaresecrets.com/everything-you-need-to-know-about-the-dual-triple-and-quad-channel-memory-architectures/3/


if he uses 2x4 and 1x8

the 2x4 will be dual while the 1x8 will be single , so once he is using more than 8G (2x4 filled) he will be using single channel again to fill the other 1x8G

___________________

While the article is correct as to older AMD mobos, this has long been a myth for newer mobos, Intel brought out what they call Flex mode years and years ago. AMD has taken the same approach, though they don't want to call it Flex as then they would have to pay Intel to use the term. Modern mobos, even many AMD mobos going back to the time of that article allow for the BIOS to simply look at the amount of memory in each channel (say 8GB in each channel (be it a single 8GB stick or 2x4GB in the 2 slots for the given channel ) and to use all 16GB in dual channel, also if Channel A has 8GB and channel B only 4GB then you would have 8GB in dual and the odd 4GB from the 8GB stick in single channel mode. More in my FAQs article (item 7) here:

http://www.tomshardware.com/answers/id-2741495/ddr3-faqs-fiction.html

Though there are no guarantees in mixing sticks from packages, which is covered in item 2 of the Fiction side of the article

Thanks for the update ...

still something is bothering me .. why do they still color the dimm slots for pairs if the system will detect it and use it anyways in dual channel mode regardless of how you install them in pairs or not ?

 

[Tradesman1]

That's for optimal use, say you have channel A (two slots 1-2) and Channel B has two also (yes i know, obviously ) 1-2, the lead slots A1 and B1 are slightly optimized to work together in a 2 stick config as are A2-B2, had a thread recently where a user was using A1 and B2 (why I don't know) and having problems galore, popped into A1-B1 and was fine (+ they've been doing it for years to help builders and for aesthetics, which hasn't always worked well, i.e. yellow and orange DRAM slots )

 

[sna]

That's for optimal use, say you have channel A (two slots 1-2) and Channel B has two also (yes i know, obviously ) 1-2, the lead slots A1 and B1 are slightly optimized to work together in a 2 stick config as are A2-B2, had a thread recently where a user was using A1 and B2 (why I don't know) and having problems galore, popped into A1-B1 and was fine (+ they've been doing it for years to help builders and for aesthetics, which hasn't always worked well, i.e. yellow and orange DRAM slots )

yes but are you sure this flex thing will work using 3 dimms only ?

I can understand it working using 2 Dimms of different sizes BUT 3 ?

2x4 and 1x8 ? I dont see any "physical" 128bit lanes between the 1x8 and the cpu ,while the 2x4 group has it.

does this mean that , the 2x4 will work 2 channel , and this group of 2x4=8 WITH the 1x8 will be virtual Dual channel too ?

I am not convinced . I think the flex mode is for the different size but those two different sized has to be in the RIGHT DIMMS PAIRED. the third one misses its pair all together...

are you sure flex can make dual channel using 3 slots ?

got the picture ?

 

[Tradesman1]

Have done it many times, each individual stick of DRAM is a single 64bit devcice, the memory controller looks to see if each channel is occupied if they are then a like amount of DRAM from each channel is 'seen' as a single 128bit device

 

[sna]

Have done it many times, each individual stick of DRAM is a single 64bit devcice, the memory controls looks to see if each channel is occupied if they are then a like amount of DRAM from each channel is 'seen' as a single 128bit device

so in theory you can now blindly insert dimms in slots in any order .. lol what if I insert 2G and 4G and 8 G in three slots ? ...

man this is crazy ...

thanks anyways lol

Edit : it gets even crazier in quad channel mode ..

lets say we insert 6 in quad channel , is this 3 in dual mode , or 6 in quad flex mode lol ?

 

[Vic 40]

You are clear on it now,but as extra info from Intel themselves,
http://www.intel.com/support/motherboards/desktop/sb/cs-011965.htm
look at "Dual-channel (interleaved) mode" -> "Dual-channel with three DIMMs".

 

[Vic 40]

so in theory you can now blindly insert dimms in slots in any order .. lol what if I insert 2G and 4G and 8 G in three slots ? ...

Depends on what is in which slot.If the 2+4 are in one channel and the 8 in the other would you get 6gb dualchannel and 2gb in single channel besides it.You can figure out the rest.

Looked at this example,

if he uses 2x4 and 1x8

the 2x4 will be dual while the 1x8 will be single , so once he is using more than 8G (2x4 filled) he will be using single channel again to fill the other 1x8G

In this case would one 4gb and the one 8gb be in one channel to work like this.

 

[sna]

After reading here :

http://www.intel.com/support/motherboards/desktop/sb/CS-011965.htm

the flex mode is not about 3 dimms is about 2 dimms of different sizes . and then will not be full dual channel but a mix of dual channel and single channel and that cant be called dual channel.

as for the 3 dimms dual channel , as seen in the link

2x2G in 2 dimms and 1x4G in the third ...

the dimm on the third is the same size of the two others so it will take the 2x2 as a 4 and dual channel with it.

not ANY size .. it has to be the RIGHT SIZE.

for example

2x2 and 8 , will not work full dual channel. it will be FLEX.

thanks every one ... but dont call FLEX dual channel. it is wrong . it is NOT.

and dont call ANY 3 dimms can work in dual channel it is also WRONG , the third must be the total size of the other 2 to work .. 2x2 and 4 , 2x4 and 8 , 2x8 and 16 and so on

as seen in the link

 

[Vic 40]

the dimm on the third is the same size of the two others so it will take the 2x2 as a 4 and dual channel with it.

not ANY size .. it has to be the RIGHT SIZE.

This is what the OP was asking about,

Is it possible to use 2x4gb + 1x8gb ram sticks if they are all of the same serie?

 

[Tradesman1]

SNA - the question here is 2x4GB + 1x8GB so 8GB in each channel = full dual channel mode (8GB in each channel under Flex), and your system will identify it as dual channel mode, if you don't want to believe, then try it and see for yourself

 

[sna]

SNA - the question here is 2x4GB + 1x8GB so 8GB in each channel = full dual channel mode (8GB in each channel under Flex), and your system will identify it as dual channel mode, if you don't want to believe, then try it and see for yourself

I got that part ty

I was talking about Mixed sizes only

btw , how about Latency ?