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Old 11-04-2012, 10:30 AM   #1
jaredimre
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Default i7 3820 not overclocked could bottleneck 680 gtx Sli?

I am going to buy a new PC with 680 gtx Sli. If I equip it with a i7 3820 not overclocked (i.e. standard 3,6 Ghz), could the 680 gtx Sli be limited by the CPU? Would a i7 3930k be a better choice? Worth spending more money? I am going to play at 1920x1080 with all filters on AA AF AO Vsync. Thanks.
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Old 11-04-2012, 10:44 AM   #2
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In a nutshell, NO. But most people will probably insist that you overclock your processor.
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Old 11-04-2012, 11:00 AM   #3
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In a nutshell, absolutely.

680SLI is bottlenecked by just about any CPU currently available.

And in fact, I get higher frames on my single 670 with an overclock on my 3770k:
http://forums.anandtech.com/showpost...58&postcount=2

For a day, I tried 670SLI on my i7-860@3.5 (~20% slower than a 3820), and I got something like 40% scaling over a single 670 in BF3.

Unless you have a good reason to go x79 (like you already have the board), just go for a 3570k or 3770k on z77. The 3820 is a terrible value for gaming. And if you're getting 680SLI, you should want to overclock, otherwise you're just wasting money.

On a more positive note, welcome to the forums, OP!
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Old 11-04-2012, 11:05 AM   #4
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Quote:
Originally Posted by Termie View Post
In a nutshell, absolutely.

680SLI is bottlenecked by just about any CPU currently available.

And in fact, I get higher frames on my single 670 with an overclock on my 3770k:
http://forums.anandtech.com/showpost...58&postcount=2

For a day, I tried 670SLI on my i7-860@3.5 (~20% slower than your CPU), and I got something like 40% scaling over a single 670 in BF3.

And welcome to the forums, OP!
Yup,a system that i had that was stolen had 2 gtx670s as well backed by a 4.2ghz 3770k and it was still bottlenecked.

It is a awesome setup that will last a while,especially when the OP swaps the chip a year or two down the road,relieving more of the bottleneck and still getting more performance.

One of the forum members aka moondogg i believe still had bottlenecking issues with his 3930k,its a waste and if anything,look no further then the 3770k.
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Old 11-04-2012, 11:15 AM   #5
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Depends on the game and the scene in the game. But often you will be bottlenecked at 1080p. You might consider playing at 2880x1620@1920x1080 (downscaling) or activate some SGSSAA - you certainly have the reserves for it in many titles.
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Old 11-04-2012, 12:02 PM   #6
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Quote:
Originally Posted by Termie View Post
In a nutshell, absolutely.

680SLI is bottlenecked by just about any CPU currently available.

And in fact, I get higher frames on my single 670 with an overclock on my 3770k:
http://forums.anandtech.com/showpost...58&postcount=2

For a day, I tried 670SLI on my i7-860@3.5 (~20% slower than a 3820), and I got something like 40% scaling over a single 670 in BF3.

Unless you have a good reason to go x79 (like you already have the board), just go for a 3570k or 3770k on z77. The 3820 is a terrible value for gaming. And if you're getting 680SLI, you should want to overclock, otherwise you're just wasting money.

On a more positive note, welcome to the forums, OP!
In Depth, I suppose you're right but there is a very fine line between bottlenecking and not bottlenecking. I'm bottlenecked right now on my single GPU by that logic, as are many others with mid-range card or low end cards..Because they can all receive a boost by overclocking the cpu. then we can start talking about how far to overclock the cpu 4.5 vs 5.0 or maybe we can go a little further and achieve a few more fps. So in theory does the bottleneck ever stop?

Last edited by Majcric; 11-04-2012 at 12:05 PM.
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Old 11-04-2012, 12:14 PM   #7
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Quote:
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In Depth, I suppose you're right but there is a very fine line between bottlenecking and not bottlenecking. I'm bottlenecked right now on my single GPU by that logic, as are many others with mid-range card or low end cards..Because they can all receive a boost by overclocking the cpu. then we can start talking about how far to overclock the cpu 4.5 vs 5.0 or maybe we can go a little further and achieve a few more fps. So in theory does the bottleneck ever stop?
At a certain point, yes, the bottleneck will shift over completely from CPU to GPU (which is generally what enthusiasts want to hear), and with a single GPU (other than a 690), I'm pretty sure that's somewhere in the >4GHz range on current Intel CPUs. The last thing to go is the minimums - that's where you continue to see the effect of a CPU bottleneck long after the averages appear identical.

But the OP is considering 680SLI, which is ~85% more powerful than a single 680, and thus while an i5/i7@4.5 is more than enough with a 680, it will definitely bottleneck two of them.

My hunch is that you'd get at least 10% better minimums and 5% averages in many games on your setup if you OC'd your 2500k to 4.0 - and you could even do that with stock voltage and stock cooling.
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Old 11-04-2012, 12:41 PM   #8
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In a nutshell, if I decide to equip my 680 gtx Sli with a 3930k rather than a 3820 what fps boost range could I expect to gain playing at 1920x1080 all filters ON (AA, AF, AO and so on)?
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Old 11-04-2012, 12:46 PM   #9
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In the vast majority of titles the 3930k wouldn't be faster. Imo the best option would be to get a 3570K or 3770K and overclock it to 4.5-5 GHz. Better (but unfortunately not available yet): Haswell.
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Old 11-04-2012, 06:01 PM   #10
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Ok, thanks. I was really impressed by these results http://forums.anandtech.com/showthread.php?t=2278579 where a 3930k performs 179 fps and a 2600K (similar to 3820) 156 fps at 1920x1080 with 690 gtx (i.e. 2x680 gtx). That's a huge difference at that resoultion. Could that be a CPU bottleneck?
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Old 11-04-2012, 06:17 PM   #11
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Quote:
Originally Posted by jaredimre View Post
Ok, thanks. I was really impressed by these results http://forums.anandtech.com/showthread.php?t=2278579 where a 3930k performs 179 fps and a 2600K (similar to 3820) 156 fps at 1920x1080 with 690 gtx (i.e. 2x680 gtx). That's a huge difference at that resoultion. Could that be a CPU bottleneck?
The frostbite engine actually does use more than four threads, and the 3930k is definitely going to be superior there. But the 3820 is a completely different beast, and not worth it. The 2600K would be equal in most cases with much lower motherboard costs.

A 3770k is superior, and factoring in total costs would be less expensive or at worst the same price.
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Old 11-04-2012, 06:41 PM   #12
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Think the 3570k will be more then enough,only a few games that maybe make a slight difference with ht.

Thought about what cpu will be replacing my locked down 2500 non k,its gonna def be a 3570k and the $100 difference could be pocketed for haswell if its a worthy upgrade.

Think a 4ghz+ 3570k would be more then plenty for a few years.
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Old 11-04-2012, 07:19 PM   #13
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@1080, yes you will be 'bottlenecked' but it will be long after you're rendering high frame rates in just about any title out there. But if you can spring for the better chip, do it, and know that you've done everything (from the consumer side) to make youre two video cards run their absolute fastest.
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Old 11-04-2012, 11:54 PM   #14
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My 2500k @ 4.5 Ghz pushes 2 7970s at 95+% usage in BF3 @ 1080P on Ultra (no CPU bottleneck present).

So the short answer is, get at least a 2500k & OC it to 4.2 - 4.5 & call it a day.
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Old 11-05-2012, 01:52 AM   #15
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i got same question .... buy my cpu is i7 3770 and i asked for 670 in sli .... is almust same as 680 in sli.....


it will bottleneck but bottleneck will be minor .... so in there future games will use your gpu more and more with forced AA and such ..... and cpu will bottleneck you less and less
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Old 11-05-2012, 01:54 AM   #16
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Quote:
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i got same question .... buy my cpu is i7 3770 and i asked for 670 in sli .... is almust same as 680 in sli.....


it will bottleneck but bottleneck will be minor .... so in there future games will use your gpu more and more with forced AA and such ..... and cpu will bottleneck you less and less
that makes no sense at all as cpu and gpu dependency can vary from game to game and the future is not going to change that.
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Old 11-05-2012, 02:04 AM   #17
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Quote:
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i got same question .... buy my cpu is i7 3770 and i asked for 670 in sli .... is almust same as 680 in sli.....


it will bottleneck but bottleneck will be minor .... so in there future games will use your gpu more and more with forced AA and such ..... and cpu will bottleneck you less and less
There is one thing you're missing if you're experiencing a CPU bottleneck:
You can enable AA/SSAA/AO etc. all you want - GPU usage may go up, but fps never will. You can introduce GPU bottlenecks in almost any game artificially so to speak, but if you're not getting the fps you want, it's a moot point.

For example look at Need for Speed Most Wanted 2012 with a 3570K@stock:

fps around 40 can be common in this game with this CPU.

You can never ever go beyond these fps, no matter what you do with your GPUs, AA etc. The only direction is down, not up. CPU OC helps of course, but only so much. What should people with a weaker CPU say? With an FX or so?
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Old 11-05-2012, 02:16 AM   #18
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Dunno what's the beef with 3820, even with the limitation compared to "k" cpus, I was able to easily oc it to 4.3ghz without messing too much with voltage and memory clock and that's decent enough oc.

I am using Gigabyte x79-UD3 with 680 SLI, I've done some research before deciding on the x79. This is the only mobo that give me 2 PCIE 3.0 slot, separated by enough space for SLI that I can easily fit 2 x 3slot 680 cards to run cooler with less noise, and with enough space in between to put in another pcie x 8 card if I need to. And this is a pretty basic mobo that's not priced like extreme gamer mobo.

For Z77, you need to have ivy bridge to run pcie 3.0, and most of the pcie spacing is not ideal. A lot of the pcie 1 and 2 are too close to run 3 slot card, and if you use pcie 1 and 3 for example, one of the slot may run at only 8x speed. Anyways, that's the situation when I was looking for a board, maybe there are now ones with better flexibility.

But just based my experience, you can build a good sli system with x79 boards, with a no frill mobo like x79-ud3. Yes there are bunch of "gamer" mobo from z77 that give you a bit better flexibility with pcie slots for sli, but you'd have to pay premium for it.

Bottomline, the cpu, chipset all perform similar. It's the feature on the mobo - for me, it's the pcie slot arrangement that will determine the best fit. I learned it the hard way already with my 7970 crossfire that 2 high powered card next to each other is not a good thing, especially running them at full load. The board that put those cards as far away from each other gets my money.
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Old 11-05-2012, 02:46 AM   #19
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ok ... i mean ... if some cpu will not bottleneck 680 in sil ... it will give like 160-180% performance ya ? but if i will put 680 sli on i7 3770 or i7 3820 .... it will give like 130-140% performance over single card and not 160-180% yes ?
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Old 11-05-2012, 03:19 AM   #20
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It all depends on the game and the settings. There is no easy answer unfortunately. Basically, the CPU should be able to maintain the fps level that you need in every game you have - and that is completely unrelated to GPUs, SLI, AA etc.

For example, guy A might need 120fps in BF3 multiplayer, so he needs a 5+ GHz Haswell. But guy B is content with 60fps and invests any headroom above that in more image quality, so for him a 2600K@4 GHz is sufficient but he might want to get a third GPU.
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Old 11-05-2012, 03:42 AM   #21
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First off I'd go with 670 SLI. A good 670 will game as well as a 680. Take the money saved and get a 3930. While there aren't very many apps/games that will scale to 12 threads today, there very well could be in a year or two. At that point you'll be happy you bought a 3930 CPU. I don't think you'll ever regret getting the 670's instead of the 680's.
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Old 11-05-2012, 06:12 AM   #22
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If I use 1920x1080 60Hz display (not 120Hz), can I see the difference between e.g. 90-100 fps and 60 fps when I play video games with Sli enabled? Do they look smoother even with a 60Hz display when reaching 100 fps instead of 60 fps?

Last edited by jaredimre; 11-05-2012 at 06:21 AM.
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Old 11-05-2012, 06:38 AM   #23
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Yes they can due to less input lag. The animations themselves are not really smoother, but the gameplay and controls are much more direct.
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Old 11-05-2012, 08:11 AM   #24
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Quote:
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First off I'd go with 670 SLI. A good 670 will game as well as a 680. Take the money saved and get a 3930. While there aren't very many apps/games that will scale to 12 threads today, there very well could be in a year or two. At that point you'll be happy you bought a 3930 CPU. I don't think you'll ever regret getting the 670's instead of the 680's.
Solid advice.
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Yes they can due to less input lag. The animations themselves are not really smoother, but the gameplay and controls are much more direct.
Exactly. The display is the last thing in line before all that computation gets to you. It literally is only a window into what is actually happening. If you speed up your FPS, the game itself becomes more responsive and smoother. I feel that this is more important with FPS, racing (which I don't play, but I hypothesize), and other "reaction-based" games.
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Old 11-05-2012, 08:25 AM   #25
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Will bottleneck you in plenty of games, most notably will be Battlefield 3. World of Warcraft would be another, but not by holding back your cards, some games just perform better the faster you clock your CPU.

Some games, like the ones I mentioned, just like more CPU power regardless of your GPUs. In other games, like say an older source game - you can be holding back your GPUs with your CPU - but it's irrelevant as it's extra power you don't even need. Just going from 150 to 180 fps. Pointless.
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