I got hold of a second 560ti 448 core and would like to SLI it into my system. I'm running the above components along with a traditional ASUS DVD RW ODD and and Carbide 500R case. I want to also OC my CPU and potentially the GFX cards, but SLI takes priority.
Use the PSU calculator on this link. The 560ti 448 needs a 550watt PSU if I remember rightly, and the i5 doesn't use as much juice overclocked compared to the AMD cpus, they have a 95 watt TDP stock so you know how much tdp headroom you have with one of those things. So yeah a good 750 watt will handle it perfectly fine
For a system using two MSI N560GTX-448 Twin Frozr III Power Edition/OC graphics cards in 2-way SLI mode a minimum of a 750 Watt or greater power supply that has a combined +12 Volt continuous current rating of 55 Amps or greater and that has at least four 6-pin PCI Express supplementary power connectors is recommended.
Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important factor.
Overclocking of the CPU and/or GPU(s) will require an additional increase to the combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclocks you are trying to achieve.
For your system configuration there should be no need to add extra capacity to the +12 Volt continuous current rating recommended above since I've already taken that into consideration. Manually overclocking the MSI N560GTX-448 Twin Frozr III Power Edition/OC from its factory overclocked settings to 820 MHz Core Clock and 1050 MHz Memory Clock will only increase the power draw by at most 11 Watts per graphics card over stock when running Furmark.
If you keep your CPU overclock to 4.6 GHz or less there should also be no need to add extra capacity to the +12 Volt continuous current rating recommended above.
The XFX ProSeries 750W Core Edition Full Wired (Bronze) (P1-750S-NLB9), with its combined +12 Volt continuous current rating of 62 Amps and with two 6-pin and two (6+2)-pin PCI Express supplementary power connectors, is sufficient to power your system configuration with two manually overclocked MSI N560GTX-448 Twin Frozr III Power Edition/OC in 2-way SLI mode.
Thank you for your responses. I especially appreciate the break-down.
@ko888, what is exactly meant by manually overclocking? Does MSI Afterburner count?
Also, does continuous current rating degrade over time? The PSU is only two months old so it's nothing to worry about right now. Still, my curiosity compels me to ask.
Manually overclocking is any overclocking that is performed using a utility like MSI Afterburner, EVGA Precision, Riva Tuner, ... etc. that will override the factory clocks that the graphics card is originally set to.
The power supply will always have the +12V current rating that it originally came with. Power supply components (i.e in particular the electrolytic capacitors) will age due to heat. The more heat that a power supply operates in, the quicker the degradation. Power supplies that are overstressed will generate considerably more heat. What happens after the capacitors have degraded is that the noise and ripple will exceed the maximum allowed by the ATX12V Power Supply Design specifications and that will cause the system to exhibit unstable behavior.