SLI / CrossFire FAQs

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mrbondj007

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Jan 13, 2013
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:eek: :eek: :eek: :eek:

great imfo so what can video cards do you recomend me for 2 monitors please
 

linkgx1

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Sep 27, 2012
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Answer still doesn't seem to be clear on whether or not two cards benefit games or not. Okay, so what about games release in the past year or two in GENERAL?

I'm really thinking about the 660 and getting anotherone later.
 

solaris11

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Aug 28, 2012
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So i can crossfire my 7950 with a 7970? Didn't know this, now I do....but i guess its more worth it to just get another 7950 since the 70 would clock down....thanks!
 

jesse-2010

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yeah you can defently team 7950 with 7970 , but it's going to go with the lower clock speed and disable the extra cores on the 7970 , you don't wana ever do this unless you have to.
 

solaris11

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Yeah after reading more I figured that out, I got excited when I saw that it could happen. Ah well. I'm very happy with my Sapphire 7950, it overclocks like a beast, and will get another one when I feel it necessary :)
 

MrWizzy2002

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Forgive me if this has been discussed before. I googled and googled and came up with no answers for these two questions. I read the OP and maybe these questions were indirectly answered by them not being covered.

Alright so here's the deets. First of all here's my setup posted on firefallthegame.com forums http://tinyurl.com/bqzl2r2. I won this PC and add a couple things. I am bran-spankin new to ati & crossfiring. I know nothing about running myltiple GPU's but am super excited to learn about everything including overclocking the 7950 since it's probably forcing the 7970 to run at a lower power to match the 7950.

1. I Didn't pay any money for anything other then the Samsung 840 Pro SSD so I did not wate any $$$$ before people start saying it was stupid of me to buy 2 different GPUs because they can't be used to their fullest. Now that's all out of the way and clear lets move on to the questions.

2. Is there a general rule/guide to follow when installing and running multiple GPU's? Should the lower end card be in the PCI slot 1 and then the higher card run in a more secondary slot? I know to try to use x16 slots first and then x8 slots when all x16 slots are used up.

3. Does it matter what card you use as your primary? I have my monitor plugged into the 7970 which is installed further away from the PCI slot 1. Maybe I should use the 7950 as primary?

I just feel a bit lost and maybe I'm not doing something right. Randomly after just sitting there the computer freezes up and I am forced to hard reboot the computer.
Thanks for your replies. Let me know if you have any questions or requests.
 

JGPenfield

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Feb 8, 2013
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My summary of what I have read. Please let me know if you agree.
SLI requires two similar cards. It would be good for a new build using the best cards available for the best performance. It would cost a lot. AMD bought ATI. Most new motherboards (AMD or Intel) support crossfire. Much fewer support SLI and if they do they also usually support crossfire.

Crossfire dose not require 2 similar cards. The performance is less than the best SLI configuration but using different cards is a significant advantage, especailly for casual computer builders such as myself.

For instance, if I build an economy system and buy a decent single crossfire card but later on want an upgraded video card I could link the two together and get an improved performance over a new video card alone. With SLI I would have to buy two new cards or the same older card that I had before. I have tried SLI in the past. I hunted for a similar old video card and found minimal improvement and plenty of glitches so I bought a single new card that out performed the two older cards linked with SLI.

So... if you are rich and a hardcore gamer or graphics person and want the very best, go with SLI. If you are a frugal hoarder that wants to keep and use all their old hardware, yet still wants to upgrade, then Crossfire is for you. How many people in thus forum fit into group 1 and how many fit into group 2?
 

WunderWuffle

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Feb 3, 2013
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Okay, I'm new to SLI's, so I'm just gonna ask a question. I'm thinking of buying another ASUS GTX 680 Direct CU II OC card, and there are gonna be 2 HDMI ports now. I was wondering if I have to plug both HDMI cables into my moniter because of this. A reply would mean a lot.
 

nukemaster

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No, you will just need the screen connected to the primary card(top in most cases). Then you just enable SLI in the Nvidia control panel and you are good to go(remember the SLI bridge connector from card to card as well).
 

WunderWuffle

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Oh thanks! I forgot all about the SLI bridge. Thanks for reply!
 

Eloy34

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Feb 11, 2013
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thanks for this info, for many months i tought that 2 video cards lets suppose, 2 5870 1 GB will mix and make 2 GB but the only thing that make the fusion is the core clock and the effective memory clock right? the memory cache still being the same.
 

nukemaster

Titan
Moderator

Yeah for the most part. It does not improve the core clock as such(it more or less splits the load), but look at one of the basic ways to use 2 cards, AFR(Alternative Frame Render).

So as the game wants frames rendered, it renders them in order 1,2,3,4,5,6,7,8 and so on. The frames are render rather fast at a rate of 60 or more as second on many games

The video cards will do this.

GPU1 Frame 1
GPU2 Frame 2
GPU1 Frame 3
GPU2 Frame 4
GPU1 Frame 5
GPU2 Frame 6
GPU1 Frame 7
GPU2 Frame 8

Since both cards are still rendering the same scene, they need to both have ALL the textures and meshes in memory.
This is why memory is not doubled, it is just more easy and faster for both cards to both have a copy of everything.

Hope this clears it up for you.
 

easyfame

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Aug 24, 2012
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guess I'll post a question. I have a 2gb 7850 but play on 4800x1200 eyefinity. Would adding another 7850 help me out with the newer games? Older games are not an issue because I max them out well anyways. after its all said and done it'll cost me around 200 dollars to do a full upgrade (selling current mobo, psu, rebates etc).

I don't want to spend 400 dollars for a new card. I'd rather spend 400 dollars changing from a "budget build" to a more future proof one.
 

Eloy34

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yes thank you very much i get it now :)
 

nukemaster

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Will you gain performance? Yes.
Will it be noticeable? It depends on the game.
Any game that is not running you low on memory should get a nice boost, but remember with both cards needing the same textures and meshes, if you exceed 2gigabytes of textures, no amount of card power will help.

4800 x 1200 seems to be a pretty good(heavy) load for a 7850.

I personally like to use a single faster card, but buying one now and another later gives many users the ability to jump in cheaper(as a higher end card cost more up front) and get an upgrade later.

While no ALL games use crossfire/sli well, AMD and Nvidia work hard to make most of them get a boost.
 

easyfame

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Aug 24, 2012
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would you say a 7950 would suffice for 4800x1200 resolution? Or is 7970 the only way to go. They both have 3gb of vram if I'm not mistaken. Its just 130ish dollars is a huge jump between the two. is it worth it?
 

nukemaster

Titan
Moderator
Well the 7970 is faster either way you look at it with an extra 256 shaders. It depends on what you want to spend and if you are willing to tune down settings.

I simply do not have an eyefinity setup to give you good insight, It is best to check out some reviews.
 

jonnyt78

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Jan 26, 2013
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If I already have the latest nVidia drivers installed on my machine (curently 314.07), do I need to remove and reinstall before adding a second 670 in SLI?
I have a second card arriving next week and all the installation guides say to remove/ reinstall drivers but I think I should just be good to add the second card and enable SLI in the nVidia control panel?
 

Maziar

Champion
Moderator

Just add the second card and enable SLI from CP and you're good to go;however,if you ran in to any color corruptions/artifacts,uninstall the drivers and perform a clean install.
 


This is a common myth that has spread like wildfire, but not true. If you use any monitoring tools, you'll see that they operate at their own clocks and do not change. There is no reason to anyways, as each card renders their own frame in AFR at least. I can't monitor the cores, but I doubt that changes either.
 

Ro2bin3son9

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Mar 18, 2013
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Also you should add that it is usually not worth it getting dual cards over a single higher end one and the reasons behind it, but still very good job.

 

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