Added add'l RAM and now SLI won't work

Hello All,

Need some advice please. I've been running my system based on the below specs (minus 6gb of ram that I just added) without any issues for the last 6mo. Yesterday, I added an add'l 6 gb of ram to my MB and now my vid cards are not working when both are installed (SLI enabled or not). When I boot to windows, my video cards are recognized in device mgr as being present, but the vid hardware is not being used (there is an exclamation next to each card in device mgr. So, basically the symptom is that the default windows resolution of 640x480 is being used and cannot be changed.

When I have 12gb or ram installed with only 1 vid card installed, all works well. Same if I remove the add'l 6gb of ram and reinstall both vid cards (as was previoulsy set up).

I'm thinking my PSU could be an issue here as it is a little light? But, before I start buying new hardware, I wanted to see if anyone had any thoughts or suggestions?

Any help is certainly appreciated!

i7 950 @3.83ghz : Gigabyte GA-X58-UD3R : 12 gb Corsair CMX6GX3M3C1600C7 @1.65v : Gigabyte GTX460 1gb SLI : OCZ600SXS 600W : Seagate ST3500320NS x2 RAID0
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  1. I think with your overclock and additional ram you might be right on the PSU being on the smaller end, although it would be sufficient based on this overclocked I7 with them in SLI total system load
  2. Best answer
    Sounds like you have two issues; first the RAM issue:

    It's always a good idea to work your way up to an overclock....

    If you CHANGE hardware you have to do it again. SO, put the CPU & RAM back to normal clocks, voltages, and timings.... and let us know.
    I've heard many, many times you can OC your RAM to 1600 with 3 sticks but bump up t 6 sticks and it doesn't work....

    Second issue; WELL ENOUGH OF THE FINE POINTS, you need more power too:

    A good rule of thumb is: 650 watts will run almost any SINGLE card..
    and 850 watts will run almost any DUAL card setup...

    I love the Corsair 850HX supplies because they remain dead silent to almost 600watts...

    You MIGHT squeak by with a really Good 650watt supply but your 600watt supply simply won't do. Check my profile, I'm drawing just over 600watts on my i7-950 with SLI 460's.. no OCs
  3. What is the OS? I've been told that the RAM on the video cards plus the MB ram counts towards the total ram that the OS can handle. Have you with the new ram gone over the amount that you OS can handle?
  4. Guys - Thanks for the input!

    @Traildriver - I'm running W7 64 bit so there is no issue with max memory limitations.

    @jb6684 - You are right on the money with your analysis! I've dialed back my overclock as you suggested and I'm able to run w/ all 12gb at stock speeds (cpu and memory). I will continue to tweak this, but at the moment I'm stable at 3.5ghz with the ram dialed back to 1552. Before adding the ram, I was stable at 3.83/1660.

    Not sure if this is a good trade off; sacrafice cpu speed for more ram?
  5. Cool, glad we were able to help you get thing up and running again!!

    Just run a few game bench marks and check your FPS with FRAPS.....

    - run at stock CPU & RAM : measure the FPS for your game demo
    - then run your 3.5Ghz OC : measure again, I'll bet you'll see just a very small change (I'm running @ 3.5Ghz too)

    I find I get more improvement in FPS by OC'ing my GPU's (but you Really should get that bigger power supply before you try this path..)

    On my i7-950 w/dual MSI Hawk Talon Attacks I run the "Call of Pripyat Benchmark"

    Resolution: 1920 x 1080 max'd out settings....

    Stock 811Mhz OC GPU 910Mhz
    min avg max min avg max
    Day 47.6 64.3 89.7 48.7 69.5 95.8

    Night 43.3 68.9 92.6 47.3 74.4 98.7

    Rain 44.5 73.5 89.9 46.8 78.9 105.5

    Sun 25.9 43.5 60.5 26.1 46.8 65.4

    But even with a 100Mhz OC on the GPUs, improves aren't really that big a deal....... 3--5 FPS

    Be sure to pick a best answer so the thread can be marked as "solved"....
  6. Best answer selected by loub71.
  7. ^ Selected your response as best answer...thanks again.

    Will take a serious look at upgrading my PSU. Although, I've had my GPU's OC'd for some time with no issues (715 stock, 800 oc). I'm also running games at 1920x1080.

    I'll run some FRAPS benchmarks and see how much of a difference there is between the 2 setups.
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