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(3) 1 Gig DDR2 memory chips...dual channel mode??

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February 18, 2007 2:50:53 AM

I have an ASUS P5W DH

I currently have 2x1 gig sticks of DDR2 667MHZ ECC memory, so I have them running in dual channel mode.

If i was to throw another 1 gig in there, is it going to do anything to my dual channel mode on my 2 gigs? Will it make everything run in single channel or can i have dual channel on my 2 gigs and single on my 1 gig? Please give me a for sure answer, I checked my user guide and couldn't find an answer to this.

thanks
February 18, 2007 4:23:26 AM

It depends on the chipset used in your MB. From what I can tell, yes, your 2GB will still be in dual-channel mode, and the extra 1GB will be in single-channel mode.
February 18, 2007 7:38:58 AM

it is a 975x chipset on an ASUS P5W DH Deluxe.

what do you mean "from what you can tell"?

thanks in advance.
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February 18, 2007 8:16:13 PM

I did a quick Google search and found that the 975X supports "Flex Memory", which I believe is what you're looking for. If you need more certainty, I'd try out google or contact the MB maker's tech support.
February 19, 2007 7:37:51 PM

Quote:
I did a quick Google search and found that the 975X supports "Flex Memory", which I believe is what you're looking for. If you need more certainty, I'd try out google or contact the MB maker's tech support.


yea i read up on flex memory and it seems as though it's just there so you can use two different memory sizes in dual channel like i coul dhave two 1gigs and 2 512 mb's, i read the whitepaper from intel about flex memory and i couldn't find anything in there about having some memory running dual channel and some at single channel....was kinda hoping someone here could take a piece of memory out of a system that had 4 chips all in dual channel installed.

thanks!!
February 19, 2007 10:32:05 PM

Quote:
...
yea i read up on flex memory and it seems as though it's just there so you can use two different memory sizes ...

Nope, it's what I suggested. Here are some quotes from the "Intel® 965 Express Chipset Family
Datasheet - For the Intel® 82Q965, 82Q963, 82G965 Graphics and Memory Controller Hub (GMCH) and Intel® 82P965 Memory
Controller Hub (MCH)" (http://download.intel.com/design/chipsets/datashts/3130...):
Quote:
Interleaved Mode
This mode provides maximum performance on real applications. Addresses are
bounced between the channels, and the switch happens after each cache line (64 byte
boundary). If two consecutive cache lines are requested, both may be retrieved
simultaneously, since they are ensured to be on opposite channels. The drawback of
Interleaved Mode is that the system designer must populate both channels of memory
such that they have equal capacity, but the technology and device width may vary
from one channel to the other.
Asymmetric Mode
This mode trades performance for system design flexibility. Unlike the previous mode,
addresses start in channel A and stay there until the end of the highest rank in
channel A, then addresses continue from the bottom of channel B to the top. Real
world applications are unlikely to make requests that alternate between addresses
that sit on opposite channels with this memory organization, so in most cases,
bandwidth will be limited to that of a single channel. The system designer can
populate or not to populate any rank on either channel, including either degenerate
single channel case.
Flex Mode
This mode provides the best performance flexibility. The lowest DRAM memory is
mapped to two channel operation and the topmost , if any, DRAM memory is mapped
to single channel operation. The drawback of Flex mode is that the system designer
must populate both channels of memory to get the benefits of flex mode, and there
will be multiple zones of dual/single channel operation across the whole of DRAM
memory.


Quote:
10.2.1.1 Rules for Populating DIMM Slots
In all modes, the frequency of system memory will be the lowest frequency of all of
the DIMMs in the system, as determined through the SPD registers on the DIMMs.
In Single Channel mode, any DIMM slot within the channel may be populated in any
order. Either channel may be used. To save power, do not populate the unused
channel.
In Dual Channel Asymmetric mode, any DIMM slot may be populated in any order.
In Dual Channel Interleaved mode, any DIMM slot may be populated in any order, but
the total memory in each channel must be the same.
In Flex memory mode, any DIMM slot may be populated in any order per channel, but
each channel must have at least 1 DIMM. The matching amount of memory per
channel will be run in Dual channel interleaved mode and the remaining unmatched
memory will run in Asymmetric mode.
February 22, 2007 5:00:11 PM

good stuff, sorry i made you find that...i really tried looking myself. I couldn't find anything that simply stated about flex mode.

thank you again!!!
!