Random reboots w/ 2 memory sticks(256) but stable w/ 1 memory stick(128)

Discussion in 'Abit' started by foobar, Jul 30, 2003.

  1. foobar

    foobar Guest

    Sorry for the long read - but I tried to provide all the detail for
    how I got to where I'm at - hope someone can provide some

    I have two(2) mushkin memory sticks (128MB PC100) that work fine alone
    but seem to be causing system problems (like random reboots) when
    installed together. I took months of on-and off H/W swapping to
    finally figure it was the memory stocks by process of elimination.
    Indeed I've had this problem since I installed the second stick 2
    years ago! Took me this long to finally feret out the cause. I've
    tried a variety of conservative BIOS memory settings - no avail - it
    all comes down to the simple combination of both sticks installed at
    the same time - no more and no less!

    By RANDOM REBOOT - I mean I'm sitting here on the web or running some
    application and suddenly - BAM! The screen goes black and it's
    rebooting like I just pressed the reset button or something! The
    computer doesn't even have to be actively doing anything - I could
    even have nothing open and not even connected. BAM! outa nowhere!

    The sytem is an ABit ZM6 w/ a Celeron 550 - it has 3 slots and
    supports up to 256mb RAM. Each slot is a 168 pin DIMM socket and has
    latest BIOS flash (some time back).

    EITHER stick of memory BY ITSELF (128mb RAM) installed in ANY slot
    works just fine - the system is ROCK solid and runs for hours, days,
    weeks, you name it! Indefinately as far as I'm concerned. Various OS's
    including 98SE and 2K Pro.

    HOWEVER... BOTH memory sticks - installed in ANY permutation of the 3
    slots (yeilding 256mb RAM) will consistently cause random hard reboots
    within a 6 to 48 hour window. WHAMO! I can on rare occasion go 3+ days
    or so w/o a random reboot. But the thing is just so darn random - it's
    hard to say - I'd say anywhere from 12 to 48 hours is pretty

    The stick decals are marked:
    1) "www.Mushkin.com PC100-222-620" (purhcased 7/99)
    2) "www.Mushkin.com PASSED CAS222 PC100" (purchased 7/01)

    I've tested each stick individually w/ MemTest86 and have a few
    occasional errors on "Test5" (Block move, 64 moves cached). But like I
    said, each by itself is great at 128MB RAM.

    I then ran memtest86 when I had BOTH sticks installed TOGETHER. LOTS
    of errors pop up especially the "Test5" mentioned above - 1000s of

    Oh yeah, I should also add that I took both sticks of memory to a
    local PC store when I finally started suspecting this was my problem.
    They tested each in their memory testers and both tested fine. But the
    guy said that software based tests like memtest86 may actually do a
    better job which was news to me.

    Sooo - any ideas? - could I have a problem w/ the memory itself?
    Appreciate any input on next steps - I'd like to have the benefit of
    the full 256MB of RAM on my system.

    foobar, Jul 30, 2003
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  2. foobar

    Wes Newell Guest

    Caps, ram or weak PS would be my wag. A larger PS may compensate for
    weak caps, but it's not really a fix.
    Wes Newell, Jul 30, 2003
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  3. Intel never made a "Celeron 550".

    It is more likely a Celeron 366 overclocked to 550, with Vcore set to
    2.2 V or higher.

    Does the ZM6 have the latest bios version?
    What are the voltage levels? (+3.3 V, +5 V, +12 V)
    Do any of the capacitors look bulging or leaking?
    Btw, what is the North-Bridge temperature when running at full load?
    I have had a few ZM6's myself, and I found out there never was any
    thermal paste below the heatsink on the NB.
    From the memtest86 website:

    "On occasion test 5/8 errors will occur even with name brand memory and
    a quality motherboard. These errors are legitimate and should be corrected."
    Maybe, but I don't think so.
    The fact that there are many more errors with both sticks in, indicates
    that the problem is somewhere else.
    A (slightly) faulty and/or over-heated memory-controller could cause it.
    A (slightly) faulty capacitor near the DIMM-slots could cause it.
    A low voltage level on the +3.3 V line could also cause it.
    ...working on it :)
    Jens C. Hansen [Odense], Jul 31, 2003
  4. foobar

    TomG Guest

    it is possible, if the ram was bought at two separate times, that they are
    just not compatible with each other for some reason. As cheap as ram is,
    would a single 256 work in that board?


    Thomas Geery
    Network+ certified

    ftp://geerynet.d2g.com Abit Mirror <----- Cable modem IP
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    TomG, Jul 31, 2003
  5. A 256 MB stick for BX/ZX-chipset, needs to be with 16 chips, and use two
    ram-banks, or in other words;
    "SDRAM at Row(s): 0 1" should show up if it is the right kind (and
    seated in DIMM1).
    It is also commonly referred to as "doublesided".
    Jens C. Hansen [Odense], Jul 31, 2003
  6. foobar

    Falkentyne Guest

    You are overclocking. And using PC100. When you overclock, two
    dimms are not going to be abs stable as 1 dimm. Normally, the
    overclock would be the cause of this, but...

    You also have other problems. The occasional errors in memtest86
    should be a huge giveaway that SOMETHING is wrong, with just one
    stick. And it takes 2 sticks to turn the problem into a disaster.

    What you need to do is inspect that board for any leaking or bulging

    If none are deformed in any way (some can still be bad, even with no
    outward signs), check the CPU; did you increase the voltage to the
    chip? RAM problems can also be caused by an unstable CPU.

    Try increasing the vcore on the CPU to 2.2v, before throwing in the

    Then, you can take the CPU and Ram to the store, test it yourself at
    100 FSB, with 2 sticks and memtest86. This will narrow it down fast
    to either motherboard or CPU. (or RAM)

    <Gibs> When you kill 6 people in Unreal Tournament
    it is "MonsterKill", In Quake3 it is "Excellent",
    in Counter-Strike it is "Kicked by console"
    Falkentyne, Jul 31, 2003
  7. foobar

    John Lewis Guest

    You are using PC100 memory.

    Are you clocking the bus at 100MHz FSB ?

    If higher, all bets are off................

    Also, if you are overclocking a 66MHz Celeron processor to 100MHz, be
    aware that its memory buffering is not as substantial as a 100MHz P3,
    and your board (like my old BH6) may not have any separate data
    buffers. The weak Celeron buffering combined with the capacitive
    load of 2 memory sticks may be enough to violate the combined
    timing spec at 100MHz, regardless of core or memory voltage

    BTW, any MemTest86 errors at all of any sort are VERY BAD NEWS !!

    John Lewis
    John Lewis, Jul 31, 2003
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