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cable 16th May, 2003 10:59 PM

let's fight the dual!
i have a ram stick that is 256MB and one that is 512 MB. i know 512 MB will run in dual channel, and 256MB will run in single channel when dual channel is run. my FSB is only 266 with my XP 2100+, so overclocking right now is no concern. when i implement this setup, which gets used up first? the single channel, then the dual channel? is this setup better than single channeling the 512MB and 256MB ram sticks? i'm afraid i might confuse my motherboard because it's not "pure" channeling and decrease performance :eek:. please help a man in need. thanks.

surlyjoe 16th May, 2003 11:02 PM

I dont believe it will run dual channel with different size sticks, will it?

Holst 16th May, 2003 11:03 PM

I dont quite understand.

If your running both sticks in different banks then you get the benefit of dual channel..

There will be virtualy no performance drop running two sticks of different sizes.

Holst 16th May, 2003 11:05 PM

you can run a 1gb DIMM and a 32mb and get dual channel benefts... although this might have some perormance hits as the 32 will fill up quickly.

With 256/512 the board will work fine.

Its only with rambus you need mached pairs, with 865/875/Nforce2 you can mix sizes with little perofrmance impact.

Uncle Bob 16th May, 2003 11:08 PM

Thanks for the info, Holst! I was under the impression they had to be same size. I see some mfgr's selling "matched sets" of memory and I, for one, have been a little suspiscious of them.

cable 16th May, 2003 11:17 PM

alright, thanks for clearing that up! however, with this setup, will dual channel be used first, or single channel? what i mean is, say for instance a game requires 250MB, does the 250MB come from the single channel, or does this come from dual channel? when does the single channel began to show itself?

jcool 16th May, 2003 11:51 PM

ALL your 768MB are DC, at least if u put one stick in Dimm1 and the other in dimms 2 or 3...

cable 16th May, 2003 11:56 PM

i forgot to mention. the 256 MB ram stick in single banked corsair XMS3200C2, and the 512MB ram stick is dual banked corsair XMS3200C2.

jcool 17th May, 2003 12:17 AM

I don't think that matters either.

Pita^Norf 17th May, 2003 12:52 AM


Originally posted by jcool
ALL your 768MB are DC, at least if u put one stick in Dimm1 and the other in dimms 2 or 3...
My understanding was if cable chose this configuration, only 512 MB will be in dual channel, the other 1/2 of his 512 stick will not be.

So was I wrong ?

Holst 17th May, 2003 01:42 AM

You are sort of wrong... and sort of not.

If you were moving a single 768mb block of data then the last 256 would be forced into the 512 stick only... single channel.

But thats not how things happen in real life.

If you are moving small its of data (even bit games textures are small compared to 512mb of ram) they will on the whole use both sticks in dual channel mode even when total memory usage is more than 512mb. The memory controller is very clever and can use both channels in a very efficent way..

Remember that the real bandwith bottlneck is the CPU itself not the memory.... so any slight drop in ineficency through running mis-matched sticks will be unoticable.

there isnt a "single bank" stick and a "dual bank stick" there are just two banks and two memory controllers both working in parralell. The type of memory you have dosent matter at all... so called "dual bank corsair" is identical to there single stick modules once there running in the machine. The only advanage of the "dual chennel packs" is having two identical sticks with the same SPD timings.

cable 17th May, 2003 03:49 AM

just to make sure i'm understanding this correctly, dual channel is always the first preference, and single channel will not take effect until after 512MB of ram is used up. right?

i don't quite understand what you meant by the bits of data stuff. say i'm playing a game like Mafia, and have the task manager open. I might see something like 400MB of physical memory being used up, and this would mean it is operating in dual channel. However, if it says (imagine lol) 650MB is being used up, what should I assume? that both dual and single channel are working simultaneously?

also, sorry if i didn't explain it better, but i didn't mean those dual packs that come with two memory sticks. here, i'll show you what i mean (just read the first sentence describing the memory):

God help me, I've been known to have a deficiency in comprehension skills :(.

bETAbILLY 17th May, 2003 03:56 AM

Dual Channel is like RAID for memory, the smallest and slowest module determines the array size and overall performance. But only in realtime.

The term matched pair applies to 2 sticks ram that display similar overclocking characteristics.

perc 17th May, 2003 07:03 AM

ok so if i use 2x256 in dual chanel mode and put a 512 in the third dimm? this well be alright also? i well still get my 128 bit mode in all thre dimms right? the manual says so but???

thx guys.. perc.

flytek 17th May, 2003 09:28 AM

a total of 512mb on each 64bit memory controller would seem the best?

cable 17th May, 2003 10:01 PM


cable 18th May, 2003 08:34 PM

holst you there? :D
or anybody else who could answer my second batch of questions? i would really appreciate it. thanks.

Holst 18th May, 2003 08:56 PM

Dual bank is different t dual DDR.

That means there are two banks in each stick, most modern memory is like this.

Somechipsets have a limitation of how many banks they can address... specifically intel ones that although they have more than two memory slots you can only use four banks.... so nornally only two reasonably big sticks..

Dual memory controlers are a different matter.

"what should I assume? that both dual and single channel are working simultaneously? "

Pretty much... if your using more than 512mb you will get a mix of dual and single usage as the smaller stick drops data and is refilled..

On a game like mafia I doubt you will use more than 512mb very often and even when you do you wont take much (if any) of a performance hit by running 256+512

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