660 SLI vs. 770 SLI - Worth the Money to Upgrade?

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chorusofone

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Hi all,

This may sound like a silly question, but I'm seriously debating the relevancy of the cost involved with this potential upgrade and whether it's realistic, or if I should just hold off for now.

I'm currently running two MSI GTX 660s (non Ti, model N660 TF 2GD5/OC) in SLI with a Corsair HX750 PSU. I'm considering upgrading to two MSI GTX 770s (model N770 TF 2GD5/OC) in SLI with a Corsair HX850 PSU. This upgrade is going to run me around $830 to $850, based on current New Egg pricing.

From what I'm gathering in my research, an 850 watt PSU will be needed for two 770s in SLI, my HX 750 just isn't going to cut it.

So, I've got about $1K to play with, give or take $100. In terms of the overall performance increase I'd get with two 770s vs. the two 660s I already have, I'm wondering if the upgrade would be worth the money I'd end up spending?

It's either that, or I'm just going to forget the whole thing and spend a little more for a Lenovo Y510p laptop for some mobile gaming.

I'm so torn right now!!! Let me know what you think. System specs detailed in my signature for more reference. Thanks!
 
Solution
cst1992
There is a very common misconception that at 80+ efficiency the PSU is able to deliver say 85% of rated power(if the readings are given that way).
The PSU is able to deliver 750W of power for almost all its life.
The real thing to think about is how much current the power supply supplies at +12V.
The HX750 that you have gives out 62A, which is 744W.
Of course, one way to say it'll deliver 650W is if it's getting old(by capacitor aging).

A 750W power supply at 80% will NOT supply 600W of power, but 750W and it will draw 937.5W from the wall at full load.
That's why people go for gold, silver, or platinum ratings, as the power drawn from the wall decreases, resulting in power savings.
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RobCrezz

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I dont think you would need to upgrade your PSU for 2x 770. your HX 750 should cope with that just fine with that.

2x GTX Titan /GTX 780 only draw 690w FULL SYSTEM DRAW, 2x 770 will be less than that.

www.overclock3d.net/reviews/gpu_displays/gigabyte_nvidia_gtx780_sli_vs_gtx_titan_sli_comparison/9
 
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chorusofone

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You know, that thought actually crossed my mind, but I really would like to keep the SLI configuration. I was originally thinking two 780s, but my budget just isn't agreeing with that right now. However, I'm assuming two 770s would surpass the performance of a single 780 Ti?

EDIT: I just took a peak at the Anandtech Bench comparison on 770 SLI vs. a single 780 Ti. You're right, that card is a total beast, but the 770 SLI config is still a little better in most cases... Now I don't know what to do... Wish I could afford two of the Ti cards and call it a day, lol
 
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HiTechObsessed

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You will actually see about the same performance between 770 SLI and a 780Ti, but like I said, the 780 Ti will be quieter, cooler and less power. Plus you can add a second Ti later :p

And with the single 780 Ti, you still have 770 SLI performance in games that don't support SLI. This is the main reason we recommend a single strong card than 2 weaker cards if you'd be buying both cards for SLI at once.

Edit: But if you're going for the cool factor, the 770 SLI is better :p

And I'm not trying to convince you either way, whatever you decide works for me, I just wanted you to see other options.
 
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chorusofone

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Wow, that's incredible. Various other resources I've been looking at have been indicating I should have at least 850 watts for two 770s or two 780s. Thanks for that info, that just made my upgrade plans a little cheaper. maybe I'll consider two 780s after all...
 
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HiTechObsessed

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You'd still want the 850. Your PSU is 80+ at 750, meaning at full efficiency it is probably only gonna be able to supply around 650w or so, which would be pushing it really close.

Pretend you decided to "spend a little more for the laptop" and use that "little more" to get you a nice 850w PSU and 2x 780s :) lol
 
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chorusofone

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Absolutely, thanks very much for your input. I do certainly understand the point behind a single strong card, makes perfect sense. In truth, this system has been my first venture into SLI, I've always run single cards in the past, and so far I'm quite pleased with the SLI outcome, so that's kind of why I was thinking on staying with an SLI config for now.

And yes, admittedly, that "cool factor" is definitely playing a part in my decision on this, as silly as it may sound. Appearance has been a huge factor with this build and I've been trying to keep an even balance between perfomance, aesthetics, and silence in operation. So far, I've acheived all three goals...
 
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chorusofone

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Oh man, stop messing with me! lol

I hear you, I figured it would be good to beef up the PSU, wasn't totally sure though. PSU requirements for video cards always tends to be a big unknown for me, seems like I'm always researching this the most when I build new systems...
 
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cst1992

cst1992

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There is a very common misconception that at 80+ efficiency the PSU is able to deliver say 85% of rated power(if the readings are given that way).
The PSU is able to deliver 750W of power for almost all its life.
The real thing to think about is how much current the power supply supplies at +12V.
The HX750 that you have gives out 62A, which is 744W.
Of course, one way to say it'll deliver 650W is if it's getting old(by capacitor aging).

A 750W power supply at 80% will NOT supply 600W of power, but 750W and it will draw 937.5W from the wall at full load.
That's why people go for gold, silver, or platinum ratings, as the power drawn from the wall decreases, resulting in power savings.
 
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Solution
HiTechObsessed

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Do you have a reputable source for this? That isn't the case... But I completely agree about amperage and quality being the most important.
 
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HiTechObsessed

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Huh, learn something new every day. Thank you for linking me there, that is very interesting. I never knew that, and have been lied to!

I retract what I said, OP, your PSU is definitely good enough. Thank you again, cst!
 
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cst1992

cst1992

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You're welcome.

@OP
Before you pull the trigger, I'd say you look at the microstuttering issue as well.
If you have experienced it before, but seem okay with it then go ahead.
I personally have never done SLI, so I don't have any personal experience with this issue, but still.
 
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chorusofone

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Great info, thanks for that! I'm not real keen on this sort of thing, but the way you explain this clears it up nicely. This made my day. I won't need a bigger PSU, even for two 780s? Good deal.

I got this system finished up in March 2013, so in terms of actual usage, the PSU isn't even a year old.

Microstutter isn't an issue that I can recall running into, to be honest. And if it is happening, I'm not noticing it, or it's not bothering me.
 
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chorusofone

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Oh, and for the record, I meant to say this earlier and got swept away in the PSU discussion, I'm using a 27" monitor @ 1920 x 1080, 2ms.

I can only imagine that even if I go with two 770s, I'm going to see some pretty dramatic differences in some instances; comparing single card to single card, the 770 seems to get an average 20 FPS improvement over the 660, generally speaking. So two in SLI? I'm thinking it would be a huge difference.

The only thing that makes me lean toward 780s instead of 770s is a little more future-proofing, so to speak. But the price difference between the 770 and 780 is where I'm left undecided.
 
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chorusofone

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Thanks to all for your input. I guess I have a decision to make and what's going to dictate that decision is ultimately where my wallet's at when the time comes to take the plunge, but you have all helped to clear a few things up. So glad I don't have to bother with another PSU. I'd hate to think I wasted my $ on the HX750. Great PSU.
 
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