XP DDR memory not listed correctly

Discussion in 'Computer Information' started by - Bobb -, May 24, 2012.

  1. - Bobb -

    - Bobb - Guest

    My daily pc has 1gb DDR400 (2 512mb sticks)
    I was tossing an old PC and took it's memory to add here, so I added another
    1gb DDR400 last night (2 -512's) and when I rebooted it shows as DDR333 in
    splash screen / XP .
    I gotta run now, but wondering - other than reseat/swap around to isolate
    etc, any tricks for troubleshooting why speed shows as incorrect ? I've
    never run into this before.

    - Bobb -, May 24, 2012
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  2. Upgrade the BIOS. It may not be recognizing the PC3200 RAM.
    David H. Lipman, May 24, 2012
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  3. - Bobb -

    Paul Guest

    Your system has an AMD processor, and this is normal.

    Clock speed is turned down on the RAM bus, when moving from
    two sticks to four sticks. The load compensation changes the
    system from DDR400 to DDR333 speed setting.

    Later RAM standards (DDR2/DDR3 versus your DDR), don't have
    this problem to nearly the same extent.

    You can use some custom RAM settings, to try to work around it,
    but then you need to do careful RAM testing before using the
    system for serious work.

    Paul, May 24, 2012
  4. - Bobb -

    VanguardLH Guest

    Some mobos have to reduce their clock rate when you populate, say, more
    than 3 memory slots. The mobo cannot support the extra load (power) at
    the higher clock rate. Another restriction may be that you lose dual
    channel mode if you go with more than 2 modules (i.e. more than 1 bank).
    Just because the mobo has 4 slots doesn't mean there isn't a consequence
    of populating more than 2 of them.

    You never mentioned the brand and model of mobo. Read its manual on
    memory support to see if there are restrictions or reductions incurred
    on memory configurations. Sometimes they just mention in a paragraph
    the restrictions. Sometimes they provide a table showing what works
    with what config.

    NOTE: For future reference and posting, when cross-posting to multiple
    newsgroups, they should be related. This is not a OS (Windows XP) issue
    but instead a hardware issue. The correct cross-post group is
    microsoft.public.windowsxp.hardware, not the windowsxp.general group.
    VanguardLH, May 24, 2012
  5. - Bobb -

    Paul Guest

    I deduced it all, and await confirmation of the missing details.

    Only AMD does this.

    My Intel chipset DDR400 motherboard has no such penalty, and
    that's how I know the processor is AMD. I can stick two or four
    matched sticks in the 875P based motherboard, and it always runs
    at DDR400. There was a claim that chipset runs Command Rate 2
    under all conditions, but without an exposed BIOS setting,
    it's hard to know that for sure. Lots of stuff about chipsets,
    can only be determined with an oscilloscope (due to the limitations
    of what is stated in data sheets).

    The OP stated a transition from two sticks to four sticks, and
    a change from DDR400 automatically to DDR333. And that pattern
    matches AMD S939 processors.

    Paul, May 24, 2012
  6. - Bobb -

    Yousuf Khan Guest

    Do all 4 sticks show as DDR333, or do some show as DDR333 while others
    show DDR400?

    What I would do is boot up with only the newer pair, and see if those by
    themselves show up as DDR400. If not, then there might be some
    incompatibility between them and your system.

    Yousuf Khan
    Yousuf Khan, May 25, 2012
  7. - Bobb -

    - Bobb - Guest

    EXACTLY right !
    ASUS mb with an AMD 939 cpu. Boy, am I glad I asked here first. It made no
    sense to me that 2 sticks to 4 would change clock speed. I don't NEED 2gb
    but I was tossing a few Celeron PC's and took their DDR400 mem sticks and
    stuck them in here rather than recycle it all.

    Thanks very much.
    - Bobb -, May 25, 2012
  8. - Bobb -

    glee Guest

    Good catch, Paul. I had nearly forgotten about this little detail about
    AMD processors at that time.
    glee, May 25, 2012
  9. - Bobb -

    Docster Guest

    I recall something call some characteristic in memory called "spd" which has
    something to do with speed detection.

    Good catch, Paul. I had nearly forgotten about this little detail about
    AMD processors at that time.
    Docster, May 25, 2012
  10. - Bobb -

    Paul Guest

    SPD stands for serial presence detect. It's a chip that holds the
    Plug and Play information for the DIMM, including memory size and
    memory timing information. It sits on a serial bus (SMBUS) and
    is read out by the BIOS when the computer starts. The serial bus
    runs at a very low speed, like around 10KHz (whereas, more
    normally, it would run at 400KHz).


    ( http://en.wikipedia.org/wiki/Serial_presence_detect )

    But the choice of DIMM memory operating speed, is up to the BIOS.
    The SPD can give info on timing settings for operating at DDR333 or DDR400,
    but the BIOS makes the decision as to what speed to run things at.
    And the "down clocking" on the S939, is a policy recommended by AMD,
    rather than being dreamed up by the manufacturer of the motherboard.

    On one AMD motherboard from that era, the user manual even contains
    a copy of the timing table from an AMD document, as if to say
    "it isn't our fault it works this way" :) I presume they did that,
    so they'd get fewer whiny phone calls at tech support.

    Paul, May 25, 2012
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