Phenom II 720 x3, 770/SB750 - DDR3 1600 runs at 1066?

I'm running:
AMD Phenom II X3 720 BE OC'd to 3.5 GHz @ 1.5V
MSI 770-C45 AM3 AMD 770 ATX (SB750)
Patriot Viper 4GB (2 x 2GB) DDR3 1600 (PC3 12800)

The RAM auto default is 1066 unganged 64-bit mode at 7-7-7-20. Attempting to set it to 1600 makes my comp freeze the instant Windows begins to load (before I get to see the Windows load screen). I read the unganged runs faster than ganged due to the Phenom's on die memory controllers. CPU-Z:

Am I missing out on a significant amount of performance here? I read that there's a glitch with Phenom II that's software related that gimps memory to make it stable, but they said it would be fixed soon and that was back in Feb. Is that fix released yet?
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More about phenom sb750 ddr3 1600 runs 1066
  1. I'm basically guessing that I need to bump the voltage to 1.9V before I can bump the frequency to 800 and AM3 BIOS doesn't support the XMP-1600 memory profile.


    I did that and configured what my BIOS let me and can get to Windows now, but this is what I'm left with. I haven't tested Prime yet, but I'm thinking if I can't reduce the cycles, I'll live with 1066 just for the tighter times.


    Prime95 caught a hardware failure right away. I'm not sure what I'm doing, but I'm tempted to let it default to 1066.


    tRAS shows only as auto in BIOS, not letting me specify, but it has tRC which says it's tRAS + tRP. I set it to 27 (tRAS 20 + tRP 7), but you see the result above. I'm able to run Prime95 with the RAM at 1.71V @ 1333.


    I got tRAS adjusted by reloading optimized defaults and running through all the tweaks again and using PGUP/PGDOWN instead of the popup. Trying it at 1600 @ 1.9V at rated specs is highly unstable even at loose timings. Trying for 6-6-6-20 was unsuccessful at 1333 @ 1.9V. I'll test this setup with Prime95.

    I guess I figured out my RAM performance worries myself. If any experienced users could review my work and say if this is a "normal" process, I'd be grateful.
  2. I think you are figuring out the process. And I think you did what so few do here - you read the threads that seemed to have similar subject matter!

    I wouldn't give up just yet. Keep exploring the BIOS options to see if you can perhaps find the "wrong" setting that's keeping you from using the full potential of this quite impressive RAM.

    The only disadvantage I can see from using this if you have to settle for 1333 is the $2 you could have saved and the heat/power drain of running at 1.9V vs 1.7V. But I guess you wouldn't be running it at 1.9V anyway. If you do end up at 1333, I'd set for 1.7V - that matches their 1333 product - likely the same RAM with a different sticker?

    Yes, I'm running unganged too. Gives one module to memory controller from what I understand, best for 2 modules.

    You mention a pop-up vs PgUp/PgDn - is this in the BIOS? If so, can't see it making a difference. Any of these settings you should be adjusting in BIOS rather than with software - at least for final testing.

    Let us know how it works out!
  3. I would make sure that you have loaded the "Optimized Defaults" at least once - and make sure you know what you've changed previously before doing so.

    You've got some interesting choices in BIOS. Might try:
    DRAM Drive Strength
    This feature allows you to control the memory data bus’ signal strength. Increasing
    the drive strength of the memory bus can increase stability during

    You've also got a dip switch on M/B that controls some FSB OC functions - make sure you know how this is set. Shouldn't affect this issue tho.

    Note these settings:
    1T /2T Memory Timing
    This field controls the SDRAM command rate. Selecting [1T ] makes SDRAM
    signal controller to run at 1T (T=clock cycles) rate. Selecting [2T] makes
    SDRAM signal controller run at 2T rate.
    Bank Interleaving
    Bank Interleaving is an important parameter for improving overclocking capability
    of memory. It allows system to access multiple banks simultaneously.

    I'd make sure it's at 2T. Interleaving don't think available with un-ganged 2 modules, not sure.
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