Results 1 to 16 of 16

Thread: 6GB vs 4GB - why 6GB slower bandwidth ?

  1. #1
    Memory Addict
    Join Date
    Aug 2002
    Location
    Brisbane, Australia
    Posts
    11,776

    Question 6GB vs 4GB - why 6GB slower bandwidth ?

    Just installed Win 2008 Enterprise 64bit for a run

    Strange that 2x2GB (4GB) is slightly faster than 2x2GB + 2x1GB (6GB) even at same timings ??? And since these results also appear in memtest it ain't just a Win2008 issue. Maybe Asus Blitz Formula related ?

    Using 2x2GB Gskill PC2-8000CL5D-4GBPQ + 2x1GB Gskill PC2-8500CL5D-2GBPK so both kits are non-Micron D9 based

    • 9x333FSB 1:1 333Mhz 2x2GB 5-5-5-15 3-42-6-3-3 memtest bandwidth = 3500+ MB/s and Super Pi 8M = 3m 24s
    • 9x333FSB 1:1 333Mhz 2x2GB + 2x1GB 5-5-5-15 3-42-6-3-3 memtest bandwidth = 2025 MB/s and Super Pi 8M = 3min 32s
    • 7.5x400FSB 4:5 500Mhz 2x2GB + 2x1GB 5-5-5-15 3-52-6-3-3 memtest bandwidth = 2994MB/s ???
    • 7.0x429FSB 4:5 536Mhz 2x2GB + 2x1GB 5-5-5-15 3-52-6-3-3 memtest bandwidth = 3212MB/s ???
    • 6.5x462FSB 5:6 554Mhz 2x2GB + 2x1GB 5-5-5-15 5-52-7-5-5 memtest bandwidth = 3186MB/s ???
    • 6.5x462FSB 5:6 554Mhz 2x2GB + 2x1GB 5-5-5-15 4-52-7-4-4 memtest bandwidth = 3249MB/s ???
    • 6.5x462FSB 5:6 554Mhz 2x2GB + 2x1GB 5-5-5-15 3-52-6-3-3 memtest bandwidth = 3315MB/s ???
    • 9.0x445FSB 4:5 556Mhz 2x2GB + 2x1GB 5-5-5-15 3-52-6-3-3 memtest bandwidth = 3329MB/s ???
    • 7.5x534FSB 1:1 534Mhz 2x2GB 5-5-3-15 3-52-6-3-3 memtest bandwidth = 5872 MB/s




    Any ideas why it 6GB config is clock for clock slower ???
    Last edited by eva2000; 03-16-2008 at 12:19 AM.
    ---

  2. #2
    Banned
    Join Date
    Jun 2006
    Location
    Durham, NC
    Posts
    2,884
    More stress on the MCH?

  3. #3
    Xtreme Member
    Join Date
    Apr 2007
    Location
    Philippines
    Posts
    312
    dual channel problems?

  4. #4
    The Blue Dolphin
    Join Date
    Nov 2004
    Location
    The Netherlands
    Posts
    2,981
    I think it has to do with bank interleaving. In this configuration the memory controller actually handles the memory as 3x2=6 (dual channel) bank whereas in a 2x2GB configuration the memory controller handles the memory as 4x2=8 banks.

    *EDIT* Looking at those numbers dual channel isn't really enabled.
    Blue Dolphin Reviews & Guides

    Blue Reviews:
    Gigabyte G-Power PRO CPU cooler
    Vantec Nexstar 3.5" external HDD enclosure
    Gigabyte Poseidon 310 case


    Blue Guides:
    Fixing a GFX BIOS checksum yourself


    98% of the internet population has a Myspace. If you're part of the 2% that isn't an emo bastard, copy and paste this into your sig.

  5. #5
    Xtreme Enthusiast
    Join Date
    Mar 2007
    Posts
    557
    I hope same size modules are installed in the same color slots?

  6. #6
    Xtreme Enthusiast
    Join Date
    Dec 2005
    Location
    Athens,Greece
    Posts
    628
    Different modules maybe result in single channel mode according to this from
    anandtech
    http://www.anandtech.com/mb/showdoc.aspx?i=3208&p=3

    Additionally, each FSB bus cycle "phase" for each channel can be further manipulated. "CHA" and "CHB" refer to the two independent memory channels in a dual-channel memory configuration. Installing only one memory DIMM, or certain combinations of mismatched memory module pairings across all four expansion slots, results in the motherboard defaulting to single-channel operation; otherwise there are two memory channels in operation, which enhances overall system performance. The number of phases per channel depends on the memory divider in use (each channel will always have the same number of channels though) - a 3:2 memory divider has two phases, 4:3 has three, and 8:5 has five, for example. We will explore the theory behind this truth shortly.
    E8400 TRUE120@Asus Maximus Formula@2x2GB Geil Evo One 800MHz 4-4-4@Corsair HX 620W
    Sapphire HD6850 1GB@Samsung 830 128GB@Casetek 1022-5@LG 19" 1970HQ
    Creative Inspire 5.1 5100@Samsung SH-S203B SA@CM Quickfire Pro Red@Logitech G-600

  7. #7
    Memory Addict
    Join Date
    Aug 2002
    Location
    Brisbane, Australia
    Posts
    11,776
    Yeah looks like dual channel isn't enabled but same sized modules are in same coloured slots. Just tried 4x1GB and it's fine i.e. 556Mhz 5-5-4-15 at 1.92v works fine with 5600+ MB/s memtest bandwidth.







    Last edited by eva2000; 03-16-2008 at 08:49 AM.
    ---

  8. #8
    Xtreme 3D Mark Team Staff
    Join Date
    Nov 2002
    Location
    Juneau Alaska
    Posts
    8,022
    odd pairings of ram has always resulted in bad results.
    its been this way as long as I could remember.




    "The command and conquer model," said the EA CEO, "doesn't work. If you think you're going to buy a developer and put your name on the label... you're making a profound mistake."

  9. #9
    c[_]
    Join Date
    Nov 2002
    Location
    Alberta, Canada
    Posts
    20,374
    number of chips (ranks more technically) on each stick of ram must match for dual channel to enable "correctly"

    All along the watchtower the watchmen watch the eternal return.

  10. #10
    Xtreme Member
    Join Date
    Feb 2008
    Posts
    189
    number of chips on all of the ram sticks, or just same for 1 and 3 (say 8 here) and same for 2 and 4 (say 16 chips here)

  11. #11
    Xtreme Enthusiast
    Join Date
    Dec 2005
    Location
    Athens,Greece
    Posts
    628
    ranks are not based on number of chips i think.
    E8400 TRUE120@Asus Maximus Formula@2x2GB Geil Evo One 800MHz 4-4-4@Corsair HX 620W
    Sapphire HD6850 1GB@Samsung 830 128GB@Casetek 1022-5@LG 19" 1970HQ
    Creative Inspire 5.1 5100@Samsung SH-S203B SA@CM Quickfire Pro Red@Logitech G-600

  12. #12
    Memory Addict
    Join Date
    Aug 2002
    Location
    Brisbane, Australia
    Posts
    11,776
    Ah ha looked into manual and it's by design that 6GB would have lower bandwidth than 4GB



    You may install varying memory sizes in Channel A and Channel B. The system maps the total size of the lower-sized channel for dual channel configuration. Any excess memory from the higher-sized channel is then mapped for single channel operation
    ---

  13. #13
    Xtreme Cruncher
    Join Date
    Jul 2006
    Posts
    638
    Enterprise Server 2007 is quite expensive. Can't believe you would buy that just to run pi...
    You have too much money eva...

  14. #14
    Memory Addict
    Join Date
    Aug 2002
    Location
    Brisbane, Australia
    Posts
    11,776
    Microsoft TechNet Direct subscription

    or the 240 day evaluation trial
    ---

  15. #15
    Xtreme Member
    Join Date
    Mar 2006
    Posts
    416
    Quote Originally Posted by Yoxxy View Post
    Enterprise Server 2007 is quite expensive. Can't believe you would buy that just to run pi...
    You have too much money eva...
    pretty sure you mean 2008, eitherway you can download the enterprise 240days trial off microsoft website.

  16. #16
    Xtreme Cruncher
    Join Date
    Jul 2006
    Posts
    638
    Quote Originally Posted by eva2000 View Post
    Microsoft TechNet Direct subscription

    or the 240 day evaluation trial
    Ah did not know there was a trial version.

    Seems like a nice OS.

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •