ABIT BD7II-RAID, max memory 2GB (in theory?)...

Discussion in 'Abit' started by Byru, Jan 14, 2006.

  1. Byru

    Byru Guest

    Hi, I have ABIT BD7II-RAID MoBo.
    Until now i was using 2 modules of 512MB Kingston Value RAM:
    KVR266X64C25/512

    I decided to upgrade the RAM (both quantity and speed) so i bought one
    module of 1GB KVR:
    KVR400X64C3A/1G

    I installed all modules (just for test :) and launched my PC.
    Everything was fine BUT:
    Windows XP SP2 sees only 1,5GB RAM (1gb module and 512mb module).
    I launched Everest, CPU-Z and Sandra and realized that all 3 apps see all
    three RAM modules, but WinXP for some reason displays only 1.5GB.
    I played a bit with the order of my modules but either way winXP sees only
    1.5 gb.
    Can my ABIT MoBo support 2gb only in 2 * 1gb modules? How is it?

    Additionally, i wanted to OC my RAM (according to some online articles that
    say my mobo can run RAM modules at 350MHz instead of 266MHz. I made it work
    with only a single module installed (for instance 512mb). When more modules
    are installed this trick doesnt work at all.

    Thx for help in advance.
    I didnt find in manual that 2gb is supported only when 2 modules are
    installed (mobo has 3 mem banks...)

    Best regards
     
    Byru, Jan 14, 2006
    #1
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  2. Byru

    Byru Guest

    Ok, according to the MoBo manual:
    "DIMM2 & DIMM3 are sharing"! :D

    Any opinion what does it mean? :D
    Byru
     
    Byru, Jan 16, 2006
    #2
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  3. Byru

    Paul Guest

    The 845E Northbridge drives a maximum of four banks of
    memory. A three slot motherboard has room for six banks of
    memory, meaning, at any one time, only four of the six
    banks have control signals available to drive them.

    DIMM slot 0 is "normal" and can accept a double sided DIMM.

    DIMM slots 1 and 2 are "crosswired", allowing one double
    sided DIMM in DIMM slot 1 or two single sided DIMMs to be
    used in slot 1 and slot 2.

    845E Northbridge datasheet - PDF page 113
    ftp://download.intel.com/design/chipsets/datashts/29074201.pdf

    "Maximum of two DIMMs, single-sided and/or double-sided"

    SCS0# -------- DIMM 0 side A

    SCS1# -------- DIMM 0 side B

    +----- SCS2# -------- DIMM 1 side A
    |
    | +-- SCS3# -------- DIMM 1 side B
    | |
    | +----------------- DIMM 2 side A
    |
    +-------------------- DIMM 2 side B

    When you plug a single sided DIMM into the DIMM 1 slot, it uses
    SCS2# chip select signal. A single sided DIMM in DIMM 2 slot uses
    SCS3# chip select signal. If a chip select signal is used by
    more than one side of a DIMM, chaos results. Plugging three
    double sided DIMMs would cause that chaos.

    Most people will use two double sided DIMMs on 845 based boards,
    leaving the third slot unused, because there are no more chip
    select signals left to address the third slot. And that is
    why the motherboard has a limit of 2GB (2x1GB) stated in the
    user mahual, as a third 1GB DIMM could not be accessed.

    My apologies if this is unclear :)

    HTH,
    Paul
     
    Paul, Jan 17, 2006
    #3
  4. Byru

    0_Qed Guest

    Paul wrote:


    ....snip...
    :)
    Excellent !!!
    Unlike the subject of the age_old "CMOS" , and it's contents,
    this "one" is "some" arcane, & hard to fathom.
    Well done.

    Added ....
    "I" learned a 'bit', here.
    Your 'bit' is a keeper.

    Since I dont have a "BD" mobo, nor the manual,
    I'd have to wonder *if* the "BD" manual explained "this" as clearly as
    you did .


    Qed.
     
    0_Qed, Jan 17, 2006
    #4
  5. Byru

    Jim Guest

    0_Qed,
    I do (both) and on page 2-3 it only states various memory
    configurations, nothing as good as Paul's explanation.
    Agreed, Paul did good!!!
     
    Jim, Jan 17, 2006
    #5
  6. Byru

    Byru Guest

    The oryginal manual states that the dimm2 and dimm3 are shared :D and gives
    a table with possible ram configs as Jim stated.

    Thank You Paul for this great answer, now i know what to eat my mobo with :D
    I just ordered second *the same* 1GB module (2 sided of course) to make the
    mobo to the max :D
    Than i will know that i made avery effort to make this old rig the best it
    could be :D
    What i can say is that it performs quite normal when compared to the newer
    rigs. The graphic benches are just a littlebit worse than in reference
    reviews ;]
    Only the memory speed is low (266) MHz but i didnt noticed games
    differenciate this taht much / because the new games run smoothly on my PC.

    One thing more, for BD7II-RAID users.
    The mobo gives the trick as i described in the first post:

    "Additionally, i wanted to OC my RAM (according to some online articles that
    say my mobo can run RAM modules at 350MHz instead of 266MHz. I made it work
    with only a single module installed (for instance 512mb). When more modules
    are installed this trick doesnt work at all."

    Fron what factor it depends i can or cannot use it?
    Can i use it when 2 modules are installed? - it never worked for me with 2
    modules, just with one ;[

    THX, Byru
     
    Byru, Jan 17, 2006
    #6
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