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Is my rig capable of running 2 660Ti's in SLI?


So I'll try to make this quick, I am wondering if my system could handle a second GPU. Here are my current specs;

Intel Core i5 2500k (3.30GHz)
Corsair Vengeance 4GB x2 (8GB)
Asus P8Z68-V PRO/GEN 3
Antec Power supply (650watt)
In Win Griffin Yellow Case
(nothing is overclocked)

I'm looking at adding a second 660Ti but don't feel like I have the technical know-how to make absolutely sure that my rig can handle it.

Now here are my concerns;

Overheating: my card runs at 70-80C after a while of gaming. My case has reasonable ventilation now, but that would get worse with a second card, I think that having 2 would make the job for each easier and thus make them cooler. But then again... less room for airflow.

Power Consumption: I know that 650 Watts is plenty for a single card, and think it should be enough for a second, but want to check in with some experts :)

Bottle Necking: I don't think this would be an issue either, but just want to make sure that neither my CPU, or my RAM, will limit what these cards can do in SLI.

Well, thanks for any help ya'll can give me.
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  1. Best answer

    Overheating: Get a second card with a non-reference cooler (MSI, Gigabyte, Asus, etc. all offer different versions) and use that if you are worried about high temps, at least you wouldn't have 2 reference cards running in your system as it seems like it's already getting very hot. Make sure you have proper ventilation, maybe replace some fans, you don't need much, just keep it smart and ethical, though your temps are not too high and should be fine.

    Power: Read this:

    IF you ever want to overclock your CPU, which you would if you're running an SLI setup to reduce any potential bottleneck and squeeze a little more performance out, you'll want a good 700 watt power supply. You don't have to go this route, but it's smarter not to cut it close when it comes to power consumption. PSU's are cheap anyways, not a big deal if you have to/want to get some more power.

    RAM has almost nothing to do with it, typically you'd want to overclock your CPU with an SLI setup, it's not required though, you could get away with stock speeds, but you'd get maybe ~10-15 FPS more depending on the game with an overclocked CPU (it's not that hard, just get like a cheapo Hyper 212 in push/pull and you're golden).

    Hope this cleared something up, feel free to ask questions.
  2. You'd also want an SLI bridge, not sure if you have one, but obviously that's what will allow the cards to work in tandem.
  3. Thanks for the reply!

    So for the "non-reference cooler" that would essentially be a 3rd party heat sink for CPUs, but intended for a graphics card instead? I didn't realize those were for anything but water-cooled systems. And I highly doubt I would have the space for something like that.

    And If I were to overclock the CPU, what software would be easiest/safest?

    Also, I do have an SLI bridge, seeing it sit there for months is part of what made me want to add a second card :)
  4. Oh, and I assume you mean just a GPU without the shroud cover that the EVGA models have? I was not thinking about that in my last post.
  5. Your PSU is more than sufficient, what resolution are you gaming at?
  6. I have two Asus 21" 1920/1080p monitors.

    So should my only concern be my CPU bottle-necking the cards? I thought more about over-heating and my case does have a huge 220cm fan on the side, and with that I think I should be fine, at least until I overclock the processor.
  7. Best answer selected by Sattooine.
  8. Sorry, I didn't see that you'd replied. This is a reference design, standard PCB (GPU Motherboard basically) and Cooler/Heatsink:

    This is a non-reference design for example, they typically offer more performance and cooling capabilities and can be paired with reference cards in SLI, though if they're overclocked they'll be downclocked to the speed of the slower card:

    Always overclock through the BIOS on your motherboard, this video should help, just search how to overclock on Asus P8Z68-V PRO or something aloing those lines and take note. Just raise the clock speeds slightly until you get a crash/BSOD, then incrementally increase the voltage. Test with Prime95 for stability. I won't go in depth here, but a little research and a decent cooler will go a long way.

    Essentially yes, though it won't be huge, you'll want a faster processor clock to compensate for the impressive amount of GPU horsepower you'll have in games. This isn't comparable to, for example (I had this setup), if you're running a Phenom II 965 BE at 3.9 GHz and a 670, where there's still a bottleneck, even with an overclock. BUT, there is a performance margine that's more evident, even in current-gen Intel CPU's at stock speeds when SLI is enabled.
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