P4 2.4c -- Do I need two memory chips for DDR?

I am new to DDR memory.. going to build a new pc with an Abit IS7, P4 2.4c , and either Kingston HyperX 3500 or Corsair XMS 3500. I want at least 512mb of memory and was just going to buy one 512mb stick. I have been reading some things about having to get two sticks of memory to make the system run in DDR mode or something. I didn't know you need two sticks of memory, I thought that only one stick would be fine. Could somebody please explain this DDR thing to me and let me know if I should get two 256mb sticks or just one 512mb stick. I will probably be overclocking this setup so I don't know if this makes a difference. Please explain so I get the fastest possible setup. And let me know what memory is the best for me and this setup.. thanks
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  1. * You've got two quality brands there but among the two listed I would choose the Corsair.

    * For Dual Channel Mode, you'll need 2(preferred) or 4 modules. Else, it will run in Single Channel Mode which means less memory bandwidth and thus less performance.

    <b><font color=blue>Logic over all.</font color=blue></b>
  2. DDR = Double Data Rate
    Read <A HREF="http://www.corsairmicro.com/main/trg-ddr.html" target="_new">this</A>

    Dual-channel memory involves 2 memory channels on your board.
    <A HREF="http://postnuke.legend.com.au/postnuke/modules.php?op=modload&name=News&file=article&sid=317" target="_new">This</A> may help, too.

    <A HREF="http://www.phototalk.net/photos/showgallery.php?cat=3394&ppuser=663" target="_new">My phototalk gallery</A>
    <font color=blue>War</font color=blue> <font color=orange>Eagle</font color=orange>
  3. OK, first lets get a few terms down:
    DDR means Double Data Rate, as in 2x transfer mode.
    QDR means Quad Data Rate, as in 4x transfer mode.

    DDR400 runs at 200MHz (200MHz with x2 transfers), and the 2.4C processor bus is QDR800, running at 200MHz with x4 transfers.

    So you can see that DDR400 (memory bus) and QDR800 (CPU bus) both run at 200MHz, "in synch" with each other so the memory controller doesn't have to be labored with conversions. But since QDR has twice the transfer rate as DDR, the CPU bus has twice the bandwidth of the memory bus!

    To correct that memory deficiency, Dual Channel mode is used. It makes 2 64-bit memory channels run as 1 128 bit channel, and requires you use your modules in matched pairs.

    While your board is capable of either Single Channel or Dual Channel operation, it will perform much better in Dual Channel mode.

    So your best performance will come from using 2 256MB modules rather than 1 512MB module.

    These chipsets are fussy about memory, I recommend you use high quality stuff, like Corsair's 3200LL (low latency) modules.

    <font color=blue>Watts mean squat if you don't have quality!</font color=blue>
  4. thanks for the advice.. so that's what all this dual channel stuff was about.. I thought it was only something to do with Athlon boards running nForce 2 or something. So really when I make my upgrade I should probably go for either 2 x 256mb modules or 2 x 512 modules huh? This will give me MUCH better performance I guess?

    As far as the memory goes... I heard the Cosair LL models aren't really recommended for the 865pe chipset. Instead just the regular pc3200 ram should be used..
    you hear the same?

    My system:
    P3 850mhz (100fsb), 512 Micron PC133, Abit SE6, IBM Deskstar 75gxp (60 gig @ 7200rpm), Hercules 3D Prophet 2 GTS (64 meg), SB Live MP3, Pioneer 16x DVD, Asus 45x CD-Rom
  5. <A HREF="http://www.anandtech.com/memory/showdoc.html?i=1828&p=5" target="_new">Here is the info you need for making your decision</A>

    <font color=blue>Watts mean squat if you don't have quality!</font color=blue>
  6. Okay maybe somebody can clear this up for me... when people talk about overclocking the P4.. I thought I heard them saying that they get their DDR memory to run at 471mhz or something like that. Now I am confused because if the P4 system bus runs at 200mhz and the ddr bus runs at 200mhz by somebody saying their DDR bus runs at 471mhz that means they are REALLY running their DDR bus as 235.5mhz right? What confuses me is that you have DDR400 and DDR433. How can even DDR433 handle a DDR471 overclocked ram bus? That is 38mhz OVER what the DDR433 can do! And then people say I can get a P4 2.4c running at 250mhz FSB (3.0ghz), meaning that would make my DDR ram's FSB go up to 500mhz and even PC3500 DDR433 has a max bus of 433mhz... this doesn't make sense..

    Second, do you need to overclock the DDR bus and the System Bus at the same time and with the same overclocking rate.
    I guess I am just trying to understand how all these crazy numbers get figured out. I see this PC3200 memory and this PC3500 memory and get confused at how the heck they get these numbers. The memory is DDR400 but PC3200.. what the heck do these number mean and how do they match up? I guess being new to the whole P4 world I feel like I am totally lost again. I just was getting the hang of the P3 land in overclocking and now it's all changed...

    My system:
    P3 850mhz (100fsb), 512 Micron PC133, Abit SE6, IBM Deskstar 75gxp (60 gig @ 7200rpm), Hercules 3D Prophet 2 GTS (64 meg), SB Live MP3, Pioneer 16x DVD, Asus 45x CD-Rom
  7. It's simple, they're all lying. It began when AMD called their 100MHz Athlon bus 200MHz, instead of DDR200.

    Since then all types of people have lied. Intel calls their 200MHz bus 800MHz, even though MHz stands for mega cycles per second, not mega transfers per second.

    Most memory can be overclocked a little bit. Some can be overclocked farther by backing off the timings (Cas Latency, etc).

    Furthermore, you can always run your memory slower than your CPU bus. While not ideal, it can allow you to get your memory to run stabley while getting more performance from your CPU. For instance, running your memory at 4/5 your CPU bus (reverse the numbers and you get CPU:RAM of 5:4), you can run your CPU at 250MHz bus and your RAM at 200MHz. You loose a bit of performance in your memory controller that way (while it does conversions), but you make up for that loss by getting mush better CPU speed.

    <font color=blue>Watts mean squat if you don't have quality!</font color=blue>
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