RAM memory slot problems on ECS mainboard model 755-A2

Discussion in 'ECS' started by Just Wondering, Feb 5, 2008.

  1. Hi,
    I own an ECS mainboard model 755-A2. It has two DIMM slots (standard
    bank 0, 1 and the other is bank 2, 3). Try as I might, even with
    matching memory sticks that came in the same package, I cannot get the
    board to work with two DIMMs installed. Has anyone else had this
    issue? I flashed the BIOS to the latest version they ever put out
    (Sept 05). It was supposed to fix the SATA controller to be able
    handle hard disks greater than 137 GB and it did---I now have a have a
    500 GB SATAII 300 drive--although I did have to hard code it via
    jumper to only pass data at the SATA I spec value of 150 MB per
    second. The BIOS update was also supposed to bring the memory
    capacity up to 4 Gig total from 2 Gig total---so I thought I could
    just return my two 1 Gig sticks and get a single 2 Gig stick to get
    the 2 Gig DDR RAM capacity I wanted on this (now) old computer. But
    Frys doesn't sell any 2 Gig sticks (except as sets of two matched 1
    Gig sticks and I tried that). So---has anyone else had any luck
    getting two sticks to work in their ECS Model 755-A2 boards?

    (BTW, the 755 board has the 754 pin processor connector for 754 pin
    AMD chips.--but I guess you guys would already know that).

    Please let me know.
    Just Wondering, Feb 5, 2008
    1. Advertisements

  2. Just Wondering

    Paul Guest

    There is a table in the manual, a table for a three slot board.
    Your board has two slots, but at least some of the principles
    should be the same.

    The Athlon64 has the memory controller inside the processor. It
    has loading limitations - the more loading on one of its address
    busses, the slower it goes. The S754 processor has two address
    busses, and one data bus. On a three slot board, one address bus
    goes to one slot, the second address bus goes to the other two
    slots. The address value on each bus, is the logical complement.
    (One bus has a 0, the other bus a 1, and the switching noise
    cancels out.) One address bus is sent the correct value, the other
    bus gets the complemented, wrong value. Only the "correct" bus gets
    the chip select asserted.

    A lot of nonsense, to make it work. The reason for a lot of this,
    is the drivers on the bus cannot be too aggressive, as the switching
    noise could potentially upset the operation of the processor core.

    With two sticks, you can help it by dropping either the memory clock,
    or setting the command rate (on other boards, the available options
    would be 1T or 2T) for command rate. With two double sided sticks
    installed, you'd expect it would not run at DDR400 Command Rate 1T,
    but somewhat lower.

    You could try dropping the "Max Memclock" in your BIOS quite a bit,
    and see if you can get the two stick memory configuration stable
    that way.

    So the recipe would be:

    1) Install just one stick.
    2) Go to the BIOS. Set "DDR Timing Setting by" to [Manual].
    Then the "Max Memclock" setting should light up. Set it to DDR200,
    instead of the more normal DDR400, or DDR333 etc. The purpose of going
    this low, is to prove that the two sticks will work under some conditions.
    3) Save and exit from the BIOS.
    4) When the board starts to POST again (you see some text), you can shut it off.
    5) Power down and *unplug* the computer. Install the second stick of
    RAM, with no power present in the computer. (If +5VSB is running,
    the RAM can be damaged.)
    6) Plug in and power up. First off, check that the board will POST with
    the new memory setting. You could go into the BIOS again and verify
    the settings are still applied (in case the BIOS is whacky, and changes
    things on its own). You should be able to exit from the BIOS, without
    saving changes.
    7) Get a copy of memtest86+ from memtest.org and test the new two stick
    configuration. (Can be run via floppy or CD.) Test for two full passes.
    This may take an hour or two. While this test is not very thorough,
    in terms of identifying problems, it is better than nothing.
    8) At this point, I'd boot a Knoppix or Ubuntu Linux CD (no hard drive needed),
    and then test with Prime95 from mersenne.org . That is a better test that
    the memory is working well. While tuning a machine, I might run Prime95
    error free for 10 minutes. If I think I've got my final, conservative
    settings, I might test for 4 hours.
    9) Fire up Windows again. Use a copy of CPUZ from cpuid.com , to verify what
    your motherboard is using for the RAM timings (like 3-3-3-8), the
    command rate (1T or 2T), and the actual clock being used for the RAM
    (DDR200 in this example).

    In terms of the aggressiveness of the settings, from most aggressive to least
    aggressive, it goes:

    DDR400 1T (typically works with one stick on an AMD channel)
    DDR400 2T (may work for two sticks on a channel - slightly better performance)
    DDR333 1T (may work for two sticks on a channel)
    DDR333 2T (should definitely work with two sticks)
    DDR200 whatever (if this doesn't work, RMA something :) )

    The timings are also important, and at DDR400, the industry standard
    (i.e. if the advert doesn't say anything) would be 3-3-3-8. The first
    number is CAS and affects performance the most. You don't want to
    dial down those numbers too much (too tight), as that can also cause

    To be able to tune the board for maximum performance, you really want
    a BIOS that exposes the four timings, the command rate, and the
    memory bus frequency. If some of those settings are missing, it
    means doing the best that you can, with less than ideal values.

    Another useful setting, is adjusting Vdimm. DDR400 memory officially uses
    2.6 volts. DDR333 or lower memory uses 2.5V. In practice, if the motherboard
    has an adjustment, you can probably apply 2.7V without a problem. (That
    is what I'm using on my current board.) The allowed spec is 2.6 +/- 0.1V,
    so 2.7V is right on the edge of that limit. And in practice, there is more
    room than that to raise the voltage. (In addition, some motherboards don't
    tell the truth - they may show 2.5, 2.6, 2.7, 2.8 in the BIOS, but the
    hardware only has two voltage values as a result of those settings. So
    the hardware capability doesn't always match the BIOS description.)

    On your board, I see a "DIMM voltage adjust", and the manual is a bit
    confused about what options it has. Either it will show a numeric
    value, or [Enabled]. In any case, try 2.6V or 2.7V, and see if the
    error rate in memtest86+ drops to zero as a result. You only want
    to apply as much voltage, as is needed to maintain a zero error rate.
    There is no point in "cooking" the RAM for nothing, unless it really
    needs it.

    Paul, Feb 5, 2008
    1. Advertisements

  3. Paul,
    Wow! I posted not really expecting an answer--but hopeful. Thank you
    so much for your response. I believe whereof you speak since you
    treated the subject so thoroughly. And I remember when I was trying
    to get it to POST that I had taken the new sticks out, re-installed my
    old stick, and crawled through all the BIOS settings and seeing the
    ones you mentioned. Unfortunately, I left all the memory settings on
    Auto except the voltage setting and did select 2.6 volts up from the
    2.55 it was set on. But that didn't post with the new sticks either
    and not really knowing what the heck I was doing, I just removed the
    new sticks and took them back to Frys. I remember looking at that
    table in the book (just as you described) and noted that the table did
    state that two sticks of dual rank DDR at 400MHz was not a
    configuration that "should" work. The highest it went for slots 1 and
    2 for dual rank sticks was 333MHz. The table did have some what I
    thought was strange possible configurations with single rank stick
    mixed with dual rank stick (and vice versa) but again---all at speeds
    below the 400 MHz setting. I only tried the 400MHz sticks because
    they were on sale for 99 bucks for the set. (old single rank DDR
    sticks that slow are getting expensive, everything is DDR2, dual rank
    and memory speeds over 800MHz any more for the "sweet spot" of low
    price and wide availability).

    Now knowing the set up tweaks you provide below (a way to go about
    exploring different BIOS settings to tune for RAM memory performance
    (in my case---at least minimal performance to get past POST) and into
    OS boot) I may give it another try with a couple sticks of dual rank
    300 MHz DDR and start with slow speed settings (limit the clock to 333
    MHz, boost the voltage select to 2.6 V, choose the CAS Timing (?) to
    3T first, if that works, try 2T, etc) I may be able to get my total
    RAM memory to 2 Gig--my ultimate goal.

    So---thanks again for the RAM memory treatise. Much appreciated.

    Just Wondering, Feb 5, 2008
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.