A7N8X-E Deluxe Dual Channel = Bad RAM? (or two modules = bad RAM?)

Discussion in 'Asus' started by Erik Harris, Nov 20, 2004.

  1. Erik Harris

    Erik Harris Guest

    Testing memory exhaustively is an incredibly slow process, so I haven't had a
    chance to troubleshoot this _fully_ yet.

    I'm running an A7N8X-E Deluxe with a "TwinX" pair of Corsair 512MB XMS PC4000
    modules (250MHz/500DDR RAM running at 200MHz/400DDR, and with default
    timings; nothing aggressive).

    Has anyone ever heard of nForce2 motherboards having trouble running
    error-free in dual channel mode? Or has anyone ever heard of two modules of
    RAM being more error prone than one?

    I just downloaded Half Life 2 from Steam, and it's crashing like crazy. I
    can't play for more than a minute or two, it seems. I've had periodic
    crashes before (two per month, maybe), with IRQL_NOT_LESS_OR_EQUAL errors,
    and one with PFN_LIST_CORRUPT (WinXP BSOD errors). And the World of Warcraft
    open beta was crashing on me regularly, too. Most other things work fine,
    and I can usually run for quite some time with no errors. I've also found
    that if I run various memory testing programs for long enough, I invariably
    find an error. It's not repeatable in a given location, but I am getting
    intermittent memory errors. I suspect that's the source of a lot of my
    crashing problems.

    So last night, I took a memory module out and ran MemTest86+. I told it to
    run all tests, but unfortunately then told it to restart the test (thinking
    that might be necessary to have all tests kick in), not realizing that doing
    so resets the settings, and it goes back to its "quick test" (which still
    takes quite awhile). This morning, I got up and checked my computer - It had
    gone through the tests 14 times and found no errors (previously, I had found
    errors within the first 2-3 passes using the same quick test and both RAM
    modules). So I swapped out the module - putting the other module back into
    its original slot, and taking the first chip out. This way, I figure I could
    narrow my problem down to a bad module OR a bad slot, and then narrow it
    further from there.

    This time, I ran ALL tests - after 2-3 hours, it was still finishing up the
    first pass (92% done or so). But so far, no errors. I'm going to keep
    testing (I needed to reboot into Windows to get some information, and figured
    I'd write this email while I did), but right now, it looks like NEITHER chip
    is bad, and NEITHER slot is bad, but the combination is bad. Is that really
    possible (or likely, for that matter)? If so, is the problem likely to be
    solved by moving the modules around such that they run in single-channel
    mode? Either way, is the fault with my Mobo or my RAM?
     
    Erik Harris, Nov 20, 2004
    #1
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  2. Erik Harris

    Paul Guest

    <<snip>>

    The Nforce2 is picky about RAM, and I consider the RAM thing to be
    the biggest exposure now with using Nforce2. I had some RAM that I
    thought was fine, but in a new A7N8X-E, it would work fine in dual
    channel, only up to 180MHz. In single channel mode (two sticks in
    slot 1 and 2), it would work up to 200MHz. My theory is, there are
    too many I/Os for the number of power/ground pins on the Nvidia
    Northbridge package, and the I/O timing slows down when both channels
    are engaged.

    Memtest86 would pass the memory, so was useless for debugging the
    problem. I found Prime95 from mersenne.org was much better, and
    it would detect an error in my case, within 30 minutes of testing.
    (Use the "torture test".)

    My solution was to buy some Ballistix PC3200, but I really don't
    know what aspect of RAM (clock speed or low latency) the Nforce2
    is really looking for. It is obvious in your case (and another case
    I read about where someone was using PC4000 memory), that clock
    speed alone seems not to be enough to fix it. Maybe the board is
    looking for low latency memory ?

    I'm having trouble correlating the symptoms, with
    how the memory works. SDRAM and DDR are synchronous technologies.
    They should only be sensitive to meeting Tsu and Th (setup and hold
    time), and not be sensitive to CAS latency. In other words, if
    normally you had a memory which was acting up, increasing the
    CAS setting by a notch (CAS2.5 to CAS3, say), would be enough to
    make a memory stable. That is a case where the internal timing is
    failing, and the CAS change solves that internal problem. But in
    the case of the Nforce2, that doesn't seem to help. In your case,
    you are using a high clock memory, and such a memory should have a
    fast clock to Q timing. But that isn't helping you. So, I'm puzzled
    as to exactly what is failing here. If the failure was external
    timing, then a memory capable of being clocked faster, should
    have helped, or at least exhibited different symptoms.

    I hate recommending a purely random purchase of RAM - you can
    visit Nforcershq and see what some of the users over there
    recommend, but I'm not sure that memory DIMM construction stays
    constant long enough, to use such a buying recommendation
    successfully. A DIMM maker can change chips at any time, which
    nullifies the benefit of shopping by brand.

    You've tried a high clock memory, so the only other type to
    try, is a low latency memory.

    HTH,
    Paul
     
    Paul, Nov 21, 2004
    #2
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  3. Erik Harris

    Erik Harris Guest

    I'm actually finding that this isn't a dual-channel problem, but a
    dual-module problem. I put the modules in the first two slots to force it
    into single-channel mode. While both chips individually check out fine, I
    get errors with both of them in single-channel mode. I'm not sure that the
    errors were as frequent as they were in dual-channel mode, so it remains to
    be seen whether or not they're enough to cause problems with any frequency.
    But if it does cause me real-world usage problems (I suspect it will), it
    looks like I may be looking into new memory. I bought Corsair XMS because it
    was supposed to be among the best memory out there, and figured that as
    finicky as the nForce2 boards are known to be with memory, that something as
    reputable as Corsair should work fine. Guess not. :(
    I haven't run Prime95 in awhile, but when I first got this system set up and
    started seeing very occasional crashes, I did run Prime95. It had no
    problems.
    I was hoping to find a workaround that didn't involve buying another gig of
    RAM. :) But if that's all I can do, I guess I'll do that, and put these
    modules up on eBay, since they're perfectly good memory modules.
     
    Erik Harris, Nov 21, 2004
    #3
  4. Erik Harris

    Erik Harris Guest

    I found my solution. After looking around, I found a Corsair help forum -
    apparently these memory modules need more power than the motherboard
    allocates to them by default. The Mobo defaults to a 2.5V DDR reference
    voltage, and the Corsair XMS chips need 2.8! I upped the voltage, and that
    seems to have done the trick. Now I just need to put them back into their
    original slots to get them back in a dual channel configuration and see if
    that works.
     
    Erik Harris, Nov 21, 2004
    #4
  5. Erik Harris

    Paul Guest

    I wish I could recommend something, but some of the stuff that works
    (like Winbond BH5 chips) aren't made any more, and what is really
    required, is a memory poll based on sticks that are currently
    available.

    http://nforcershq.com/forum/viewtopic.php?t=2482

    (Memory poll)
    http://nforcershq.com/forum/viewtopic.php?t=7824

    Perhaps you could contact Corsair on their help forum:
    http://www.houseofhelp.com/v2/forumdisplay.php?forumid=128

    Maybe they can be convinced to swap the PC4000 for something
    known to work well on Nforce2. (3200XL?)

    Have you tried bumping up the memory voltage ?
    Just enough to see if the error rate responds to a voltage
    change or not.
    http://www.houseofhelp.com/v2/showthread.php?t=32391

    http://compatible.corsairmemory.com/Default.aspx
    I guess they think Nforce2 works with just about anything...
    http://compatible.corsairmemory.com/memorysearch.aspx?modelid=461

    They actually claim to test with A7N8X here:
    http://www.houseofhelp.com/forums/showthread.php?s=&threadid=8048

    HTH,
    Paul
     
    Paul, Nov 21, 2004
    #5
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