A8N-SLI Prem Memory Expansion Problem

Discussion in 'Asus' started by csm, Aug 14, 2005.

  1. csm

    csm Guest

    I have a new ASUS A8N-SLI Premium MB with 1 gig (2x512MB 400MHz -
    TWINX1024-3200C2PT) of Corsair XMS Platinum series DDR. The memory is
    installed in the A-1 & B-1 slots. Everything works OK. However, when I add
    a second gig of Corsair non-Platinum series (2x512MB 400MHz -
    TWINX1024-3200C2) DDR memory to the A-2 and B-2 slots, the system will not
    boot and the screen stays off. I have also paired the Platinum Series
    memory to A-1 & A-2 and Non-Platinum series to B-1 & B-2 with no success.

    Any ideas?

    csm, Aug 14, 2005
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  2. csm

    Odie Ferrous Guest

    This board (and I imagine *any* 939 board) is an absolute pain to work
    with if you need lots of memory.

    It doesn't like all four slots being filled; ASUS documentation
    explicitly mentions you need single-sided memory in banks 3 and 4.

    Even then, memory speed drops from 400 to 333; apparently this can be
    forced back up to 400, but what effect it has on stability is anyone's

    I'm forced to running this board with 2GB of memory, when I ideally need
    a minimum of 4GB.

    Odie Ferrous, Aug 14, 2005
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  3. csm

    Paul Guest

    Try a pair of DIMMs in A1-B1 and check that the BIOS
    reports dual channel and all (1GB) of memory is reported.

    Repeat for A2-B2 slots.

    The purpose of doing this, is to rule out a bad DIMM slot
    or a bad chip select signal on the processor memory controller.

    I've read a few posts now, where the Asus BIOS is using
    a riduculous set of criterion for DIMM matching. I do seem
    to remember reading somewhere, that they wanted four
    identical DIMMs, but identical according to AMD, is to
    match rows, columns, banks, and ranks. I think AMD also
    wanted the same CAS for each DIMM, but I don't see that
    as being a necessary requirement (previous motherboards have
    survived quite nicely by selecting the slowest DIMM, to set
    the timing on the controller). Document 26094 on the
    AMD site contains all you could ever want to know about
    "BIOS Writers guide" to the Athlon64 family, and Asus
    doesn't seem to be doing exactly as the guide suggests.

    It could be that this is one of those matching problems. Now,
    in your case, if I go to the corsairmicro.com website, and
    download datasheets for your two pairs of DIMMs, of course
    they have the exact same specs. They are only supposed to
    differ in the heat spreader on the module. However, you should
    still get a copy of CPUZ from cpuid.com , and dump the
    contents of each DIMM's SPD, and see to what extent the DIMMs
    are the same. One DIMM will have a product name with the
    word "Platinum" in it, which is a difference, but Asus should
    not be comparing vendor strings on all four DIMMs for a

    In one case I read about, similar to your module choices,
    the poster could not get the second set of DIMMs to be
    seen by the BIOS. Only one pair would register and be
    counted during the BIOS RAM test. Your symptoms are
    a bit different than that, but it is the same issue, with
    a crappy decision tree in the BIOS when dealing with
    four DIMMs.

    Other reauirements are, if operating at DDR333, then command
    rate 1T timing should be OK. If operating at DDR400 with
    your four DIMMs, then command rate 2T should work. DDR400 2T
    is slightly faster than DDR333 1T. In one of the Anandtech
    articles for the A8V Deluxe (an earlier board), they found -

    "The A8V Deluxe is also very picky about the settings that
    are used with 4 dimms in the 'Enable 2T' option in BIOS.
    If an Auto setting is used with 4 dimms the board tries to set
    1T and single channel memory at a lower memory speed. If 'Auto'
    is selected and memory timings are forced to DDR400 the board
    would not boot. With 4 dimms, you will need to set the 2T
    option to 'Enable 2T' for proper Dual-Channel operation
    at DDR400."

    Perhaps your BIOS has the same bug ? Try setting the Enable 2T
    option so the BIOS has no choice but to use 2T timings, before
    installing the second set of sticks. Maybe that will coax some
    life from it.

    Paul, Aug 14, 2005
  4. csm

    csm Guest

    FOLLOWUP: I purchased an identical 1 gig (2x512MB 400MHz -
    TWINX1024-3200C2PT) of Corsair XMS Platinum series DDR memory to match the
    previous gig. Same problem. All 4 slots filled with identical DDR memory.
    I don't think this Corsair works in 4 strip configuration. I'm going to
    take the extra gig back and look for 2 strips of 1 gig each to get to 2
    gigs. I'm going to give up on the 4 strip configuration.

    ASUS A8N-SLI Premium MB - v1005 BIOS
    AMD Athlon 64 3800+
    1 Gig Corsair Platinum Series (2x512MB 400MHz - TWINX1024-3200C2PT)
    1 Maxtor SATA 250 16meg cache 7200RPM HD
    2 Maxtor SATA 120 8meg cache 7200RPM HD (Raid-Striped)
    BFG nVidia 6800GT PCIe

    csm, Aug 15, 2005
  5. csm

    csm Guest

    csm, Aug 15, 2005
  6. csm

    Paul Guest

    Did you try setting "Enable 2T" command rate, before installing
    the second pair ? Crank the memory clock down to DDR333, and see
    if that is enough. I want to be able to distinguish between a
    matching failure problem, versus using too aggressive a setting
    for the memory clock or the command rate.

    Also, with your two sets of Platinum, compare their SPD contents
    with CPUZ from www.cpuid.com . Perhaps there is still a difference
    between them.

    Paul, Aug 15, 2005
  7. csm

    csm Guest


    I'll try that next. However, I did try it with 3 strips installed. The
    system booted in single mode with 1.5 gigs of ram. Either strip worked in
    either of the remaining slots (A2 & B2). There is a lot of talk on the ASUS
    site. Appears to be an ongoing problem.

    csm, Aug 15, 2005
  8. csm

    Paul Guest

    That means you have a Rev.E processor. According to the 26094 AMD
    document, Rev.E processors now have the ability to use all slots
    in single channel (64 bit) memory mode. That is why three sticks
    worked and all the memory (1.5GB) was detected. If you had a
    release of processor previous to Rev.E, either the computer
    wouldn't POST in that config, or some of the memory would not
    be detected.

    Previous to Rev.E

    1 stick (use B1 or B2, as Ax slots won't work)
    2 sticks (B1 & B2 - single channel, A1 & B1 - dual channel,
    A2 & B2 - dual channel)
    4 sticks (pair in A1 & B1, pair in A2 & B2, less hassle if all
    DIMMs identical, unclear what rules the BIOS is using)


    1,2,3, or 4 sticks now possible.
    Sticks can now be placed in the Ax slots, whereas before
    Ax slots were only to be used for dual channel configurations.
    B is no longer the "primary bus", A and B bus are equals.

    Combinations which are not paired, revert to single channel
    64 bit mode. If your DIMMs are not matched to the BIOSes
    satisfaction, it will throw the board into single channel
    mode. 2 unmatched sticks, 4 unmatched sticks, and any kind
    of 3 sticks, can give single channel mode.

    It sounds like the BIOS decision tree is a mess. Maybe
    they should get their "A+" BIOS team working on this,
    instead of their "maintainer" team. (The maintainer team
    are those guys who make broken BIOS releases at release
    levels like 1021 :)

    I guess what we need to find now, is someone who got four
    sticks to work. And then ask them why it works...

    Paul, Aug 15, 2005
  9. csm

    csm Guest

    Thanks for all the great help and ideas. I took back the TWINX1024 strips,
    shelled out the extra money and purchased the TWINX2048 and its up and
    running with 2 gigs of ram in the dual chan mode. It will be interesting to
    see what, if anything, ASUS does.

    Great Group!
    csm, Aug 16, 2005
  10. I'm sure this is a stupid question but -

    How do I tell if my A8v deluxe is running in dual channel mode - does the
    bios report this during the boot phase like the Giabyte boards?

    CPU-Z reports that the memory channels are dual and that the frequency is
    166.7 - does this mean dual channel at 333 mhz?

    I have corsair double sided ram - get the same result with 1 stick in A1 and
    1 in B1 as I do with all slots filled.

    thanks in advance.
    Peter Seymour, Aug 22, 2005
  11. csm

    Mark A Guest

    The A8N bios will indicate whether memory is in dual channel mode (disable
    the fast boot so you can see it easier before it rolls off the screen).
    Don't know about the A8V bios.
    Mark A, Aug 22, 2005
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