Question about adding RAM (DDR2) in dual-channel; amount per banks, etc.


G

Gary Seven

Hello all.

I am getting ready to rebuild my aging and decaying machine of five years.
I'll probably either buy the Asus M2N1394 or the M2NPV-VM. Here are the
links if anyone's interested:
http://www.asus.com/products4.aspx?modelmenu=2&model=1386&l1=3&l2=101&l3=340&l4=0

http://www.asus.com/products4.aspx?modelmenu=1&model=1138&l1=3&l2=101&l3=296

My question is about how much DDR2 RAM to install. For purely practical
reasons I'd like to install 4GB in the form of one 2-GB stick in each
channel (ie, 2GB in channel A and 2GB in channel B) to not only maintain
"dual channel mode" but also to stuff the mobo with as much as the OS can
handle. I realize that using a 32-bit OS like WinXP Pro that not all 4GB
will be addressed and there will be some waste.

Is it possible then, to install say a 2GB stick in one channel and then a
1GB stick in the other channel for a total of 3GB RAM and **still** maintain
the "dual channel" mode? I don't have clear if to be in dual channel you
have to have the exact same amount of RAM installed in each socket
(channel). If it were up to you (price not a consideration) is it "best" to
go with 3 or 4GB total?

TIA to all.
/G7
 
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C

chrisv

Gary said:
My question is about how much DDR2 RAM to install. For purely practical
reasons I'd like to install 4GB in the form of one 2-GB stick in each
channel (ie, 2GB in channel A and 2GB in channel B) to not only maintain
"dual channel mode" but also to stuff the mobo with as much as the OS can
handle. I realize that using a 32-bit OS like WinXP Pro that not all 4GB
will be addressed and there will be some waste.

Is it possible then, to install say a 2GB stick in one channel and then a
1GB stick in the other channel for a total of 3GB RAM and **still** maintain
the "dual channel" mode? I don't have clear if to be in dual channel you
have to have the exact same amount of RAM installed in each socket
(channel). If it were up to you (price not a consideration) is it "best" to
go with 3 or 4GB total?

They need to match. Just go with 4GB.
 
Y

Yousuf Khan

Gary said:
Is it possible then, to install say a 2GB stick in one channel and then a
1GB stick in the other channel for a total of 3GB RAM and **still** maintain
the "dual channel" mode? I don't have clear if to be in dual channel you
have to have the exact same amount of RAM installed in each socket
(channel). If it were up to you (price not a consideration) is it "best" to
go with 3 or 4GB total?


I got the M2NPV-VM, with 4GB on it. I see only a bit over 3GB on WinXP,
but a bit under 4GB in Linux 64-bit (a bit of it is shared by onboard
video).

Yousuf Khan
 
Y

Yousuf Khan

Gary said:
Is it possible then, to install say a 2GB stick in one channel and then a
1GB stick in the other channel for a total of 3GB RAM and **still** maintain
the "dual channel" mode? I don't have clear if to be in dual channel you
have to have the exact same amount of RAM installed in each socket
(channel). If it were up to you (price not a consideration) is it "best" to
go with 3 or 4GB total?

Oh BTW,

Not only is it impossible to get dual-channel mode when using a stick of
1GB and 2GB, you sometimes won't even get dual-channel if you got two
sticks of 1GB or 2GB. The two sticks have to be absolutely identically
matched in micro-architecture (same number of chips per circuit board).

Yousuf Khan
 
N

Nate Edel

Gary Seven said:
Is it possible then, to install say a 2GB stick in one channel and then a
1GB stick in the other channel for a total of 3GB RAM and **still** maintain
the "dual channel" mode? I don't have clear if to be in dual channel you
have to have the exact same amount of RAM installed in each socket
(channel). If it were up to you (price not a consideration) is it "best" to
go with 3 or 4GB total?

Short answer: they have to match.

Longer answer: that's true for the overwhelmingly vast majority of
chipsets (and thus motherboards) on the market, ever. I believe a couple of
high-end chipsets have supported an "asymmetric mode" where sticks of
different size but similar timing could be used for dual-channel mode
(although accesses to the "higher memory" on the unmatched DIMM would be
slower.)

I don't think any of those survive on the market today.
 
G

Gary Seven

: Gary Seven wrote:
:
:: My question is about how much DDR2 RAM to install. For
:: purely practical reasons I'd like to install 4GB in the form
:: of one 2-GB stick in each channel (ie, 2GB in channel A and
:: 2GB in channel B) to not only maintain "dual channel mode"
:: but also to stuff the mobo with as much as the OS can handle.
:: I realize that using a 32-bit OS like WinXP Pro that not all
:: 4GB will be addressed and there will be some waste.
::
:: Is it possible then, to install say a 2GB stick in one
:: channel and then a 1GB stick in the other channel for a total
:: of 3GB RAM and **still** maintain the "dual channel" mode? I
:: don't have clear if to be in dual channel you have to have
:: the exact same amount of RAM installed in each socket
:: (channel). If it were up to you (price not a consideration)
:: is it "best" to go with 3 or 4GB total?
:
: They need to match. Just go with 4GB.

Yeah, you're right. That's exactly what I'm going to do. :)

/G7
 
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G

Gary Seven

: Gary Seven wrote:
:: Is it possible then, to install say a 2GB stick in one
:: channel and then a 1GB stick in the other channel for a total
:: of 3GB RAM and **still** maintain the "dual channel" mode? I
:: don't have clear if to be in dual channel you have to have
:: the exact same amount of RAM installed in each socket
:: (channel). If it were up to you (price not a consideration)
:: is it "best" to go with 3 or 4GB total?
:
: Oh BTW,
:
: Not only is it impossible to get dual-channel mode when using
: a stick of 1GB and 2GB, you sometimes won't even get
: dual-channel if you got two sticks of 1GB or 2GB. The two
: sticks have to be absolutely identically matched in
: micro-architecture (same number of chips per circuit board).

Thanks Yousuf. So I guess it makes sense then (given what you said that the
sticks have to be absolutely matched) to buy the memory from Crucial in one
of their "kit" packages. In this case, the 4GB "kit" which consists of two,
2GB sticks.
/G7
 
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Y

Yousuf Khan

Gary said:
Thanks Yousuf. So I guess it makes sense then (given what you said that the
sticks have to be absolutely matched) to buy the memory from Crucial in one
of their "kit" packages. In this case, the 4GB "kit" which consists of two,
2GB sticks.


You don't have to buy it from Crucial. Just buy it from anyone, as long
as you get two of exactly the same thing.

Yousuf Khan
 

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