sli 780 and seprate power supplies

Hello friends.. I have been considering selling my 780 and spending a little extra to purchase a 980 strix.

For the time being though I have found a second 780 on the cheap local craigslist and thinking about putting in my rig with a second smaller power supply corsair cx600m powering just the second card.  since i have the power supply just sitting on my shelf and no desire to purchase another larger one when the prospect of the 980 is looming.
 I usually run two monitors a 60hz acer with good color and an asus vg248qe at 144hz. I do have a couple questions before i do this though and if anyone knows the answers or shares an opinion, ill buy you a cookie.

First, is there any issues running a seperate power supply just powering the second card?
Second, my goal is to get the highest or full 144 fps out of the asus 248qe. Any opinions on SLI vs 980 for pushing FPS at 1080p consistently?

With 1 780 currently even Overclocked games like Shadows of Mordor hang around 35 - 70 FPS without the high res package installed.
 I know both are overkill for 1080p but I really enjoy high FPS and smooth gameplay on ultra and maxed settings.  I am not interested in moving up in resolution until i can afford/achieve FPS over 100 consistently as for me this makes more of a visual impression than just higher resolution at lower FPS. I dont know if i am sensitive but the screen stutter/micro stutter at lower FPS is really noticeable for me and sometimes gives me a headache.    For my Budget and current tech those framerates at higher resolutions are not yet attainable.

any and all opinions info are welcome :)

Ah hah!  Thank you bprat i knew there would be something i did not think of.

 I am just thinking of using it because its free and another 750+ watt is another 100 - 150 dollars miniimum for a decent one that will support both cards. and i currently have the cx600m and a very nice sea sonic 660 platinum. 

What case do you have?  You have room for two PSU's?  Hopefully you're looking into which PSU's your buying for noise and heat reasons. 

Fun fact (I like to spread these).  Look at how much of a load they need to achieve that efficiency that you're buying.  So if you have two 600w PSU's. One is 80+ Gold and one is 80+ bronze.  The bronze is $50 and the gold is $90.  But it's only rated at gold if you achieve 80% or higher load.  So bronze would be better as it has better efficiency at lower loads.

True, but remember one 980 out performs a GTX Titan Black. Of course if you already have a GTX 780 it is cheaper to just buy another 780 rather than sell current one and buy one 980. 2x 780 is > one 980.

Recommended minimum psu for sli 980 is about 800watts.   One site mentions a 750 watt, but that's bare minimum with little or no overclocking going on.    I'd get a 850 myself if buying new. 

Good idea.

I tend to go higher than needed for the psu, mainly because , first I'm 'old school ' where you needed gobs of power at one time, and second, when a psu goes over the 80% rated output, meaning 600watts on a 750 w psu, then more heat builds , and the logic voltage become not as stable.  The better units can take it, but still, over time, components wear and a faulty or stressed  psu will cause roll overs, bsod,etc and the psu tends to be the last thing people consider.

Just me. 




Edited by bprat22 - 18 Oct 2014 at 9:47am

http://www.seasonicusa.com/Platinum_Series_XP2.htm

This is what I am currently using in the 660. Variant mostly for the high 12v rail output. I don't understand how it all works. But if you can confirm the 99% rating keeps the voltage within ¹% of the target required load? When I look at the graphs the power seems very steady is comparison to the cx600 that I also checked the graphs on.

This is whey I love posting questions here even when they are seemingly silly at first
you guys are awesome and every time i learn something. Professor BP and Meller your depth of knowledge is awesome!