Dual Channel Question

Hatman

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Is it only 2 modules that cna run in dual channel?

So if I had 3 modules could i run them all in dual channel none in dual channel or 2 in dual channel and 1 normally.

Also can 4 ddr2's be used in dual channel? Or quad channel or w/e.

Thanks.
 

betzibu

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If you have 3 modules you run two (must be same manufacturer and model and placed in the right place on the MB) in dual channel and one in single channel.
 

lancer_3k

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I'm not so sure... As far as I know since dual channel is essentially you reading data symmetrically across 2 modules to "pretend" to have twice the memory bus speed, I don't think you can mix an odd number up and still have dual channel working. So you can't have dual channel memory unless ALL of it exists in pairs, eh.
 

betzibu

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Yeah... I take back what I said before. I tried this now and with 2 and when I start my computer it says that it's in Dual Channel but when I add the third one, it's gone. It seemed logical in MY head :p.

But actually, it depends on the motherboard. As you can see on the end of this document HERE for the ASUS P5B Deluxe 3 RAM sticks in dual channel is possible for some vendors.

Read your MB manual or check the manufacturer's and see if it's possible.
 

samsayit

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I'm not so sure... As far as I know since dual channel is essentially you reading data symmetrically across 2 modules to "pretend" to have twice the memory bus speed, I don't think you can mix an odd number up and still have dual channel working. So you can't have dual channel memory unless ALL of it exists in pairs, eh.

I think so too. Either use one or two pairs of identical sticks. Adding a third would mean that one channel has more memory than the other channel, and thus they're not symetrical.
 
Intel has some kind of dual channel with mixed sizes. its not quite as good as matched pairs but it works. I am not sure what they have on the AMD front as before this i had a A64 3200+ for 754 :)

I currently run 2 1024 stick and 2 512 sticks with no problems. I think that may be the best way to go(4 sticks). But be aware some chipsets used to drop the ram speed to 333(754 and 939, not sure about AM2 ddr2 667 anyone?) when there was more then 2 sticks
 

jonisginger

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So, in summary

To have dual channel you must have a multiple of 2 sticks.

Placed in the right slots. on some motherboards they are next to each other, but in any case, they should be different colours.

If you have 3, it will in all run in single channel mode.

You can get quad channel, but if you do, your penis size does shrink *serious face* 8O

Quad channel DDR2 800 would give you a bandwidth of around 32M/b a second.

Hope that helps
 

Hatman

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From what I understand rather than just getting "quad channel" you get "dual dual channel" lol.

IE you got 4slots on MOBO and 2 run in dual channel and so do the other 2.

So rahter than 64bit/sec by a normal module u get 128bit/sec from all.
 

bc4

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my intel mobo instruction book lists another way to achieve dual channel... I'm not sure about other mobo's but i'd guess they'd be similar.

have 2 x 512 mb in channel A + 1 gb (1 dimm) in channel B
if you the same speed ram then the above config will run 2 gb dual channel

I've never tried this but it is in my manual and thought it might help with the question
 

Mondoman

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To have dual channel you must have a multiple of 2 sticks.
It depends on your MB/chipset. You need to have the same amount of RAM in each channel (except for recent Intel chipsets, which can run dual-channel on the "matching" parts of the two channels even if one channel has more than the other); some chipsets (especially older chipsets and non-Intel chipsets) require that you use pairs of DIMMs, one member in each channel, with each pair being the same size, or sometimes the same internal organization or even "identical".

...Placed in the right slots. ... in any case, they should be different colours.
It depends on the MB; sometimes you use the same colors, sometimes you use different colors.

...If you have 3, it will in all run in single channel mode.
It depends on your chipset -- see first answer above.
 

lazio313

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if you ran 2x512 and 2x1gigs. would this work in dual channel? i mean if its paired then it sounds like yes, but i was just thinking if its all symmetrical then no because of the extra 512 on each of the 1gig sticks.
 

jonisginger

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Not sure, for sure the two 512mb would work dual channel as long as they are the same type. Don't think the 1gb will :S ask the guy who corrected me three times lol he knows what hes on about
 

Captain_Soviet

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my intel mobo instruction book lists another way to achieve dual channel... I'm not sure about other mobo's but i'd guess they'd be similar.

have 2 x 512 mb in channel A + 1 gb (1 dimm) in channel B
if you the same speed ram then the above config will run 2 gb dual channel

I've never tried this but it is in my manual and thought it might help with the question

That is true, I'm doing that right now. I have an Nforce 4 mobo, and as long as the amount of memory in each channel is the same, it will run in dual-channel mode. I have 2 512 Mb sticks in channel A, and a 1 Gb stick in channel B. It's fairly stable, but since my memory and mobo are slowly dying thanks to a power supply that died earlier, sometimes it won't boot.