Dual channel

  • Thread starter Thread starter Roy Coorne
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Roy Coorne

RDellinger said:
Do you have to do anything when you install memory for dual channel
to work beswides putting the memory in the right slots? Thanks
Click to expand...

No - if you have two matching ('identical') memory modules...
 
Do you have to do anything when you install memory for dual channel
to work beswides putting the memory in the right slots? Thanks
 
RDellinger said:
As in PC3200 333 mhz? Or also the same maufacturer??
Click to expand...

The degree of matching depends on the chipset. The dual channel
implementations are not all the same. The Nvidia NForce2 has
demonstrated itself to have independent memory controllers, so
the matching consists of matching the amount of memory on each
channel, and operating the memory at a mutually agreeable speed.
For example, if you mixed a 512MB PC2700 with a 512MB PC3200,
then when plugged into the appropriate slots, they could be
operated at DDR333. It even operates in dual channel mode
when the amount of memory mismatches, but that means the
unmatched portion of memory runs in single channel mode
(it doesn't have a choice - it is physics).

An Intel 875/865 chipset operates the DIMM slots in "UberDIMM"
mode. AFAIK this means one memory controller develops signals
for two slots, so the sticks have to behave exactly the same way.
I haven't read a lot of posts about attempts to match to different
degrees, but I suspect "identical" sticks would help on that
platform. See page 11 of this guide.

ftp://download.intel.com/design/chipsets/applnots/25273001.pdf

For the Athlon FX, AMD provides some useful info. See pg.143

http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26094.PDF

// Special case
if ((DimmLowSize == 1024MB) && (DimmLowDevWidth == x8) &&
(DimmLowNRanks== 2) && (DimmHighSize == 512MB) &&
(DimmHighDevWidth == x16) && (DimmHighNRanks == 1))
DramMode = 64-bit;
// General case
else{
if (DimmLowSize <= DimmHighSize){
DramMode = 128-bit;
}
else{
if (DimmLowSize == DimmHighSize * 2){
if ((DimmLowNRanks == 1) && (DimmHighNRanks == 2)){
DramMode = 64-bit;
}
else{
DramMode = 128-bit;
}
else{
DramMode = 64-bit;
}
}
}

If you can understand that pseudocode, you are a better person than me :-)

HTH,
Paul
 
RDellinger said:
Do you have to do anything when you install memory for dual channel
to work beswides putting the memory in the right slots? Thanks
Click to expand...

No. Even if you don't have matching memory*.

I know this works well on nForce (AMD), and there is no reason why it
shouldn't on Intel - provided you set the timings manually.

Ben
 
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