SLI / CrossFire FAQs

Hey guys/girls
I have seen many people making mistakes about MultiGPU technology or have difficulties understanding; therefore,I decided to write a guide that helps you understand it better.
So,let's start!

What is SLI ?
NVIDIA SLI is a platform that allows you to scale graphics performance by combining multiple NVIDIA graphics solutions in a single system.

What is Nvidia Hybrid SLI?
From Hothardware.com :
NVIDIA's Hybrid SLI technology gives users the ability to pair an IGP, or mGPU (motherboard GPU), with a discreet graphics card, or cards, for two new modes of operation. NVIDIA calls these new modes Hybrid Power and GeForce Boost.
GeForce Boost does what its name suggests. By coupling the motherboard's integrated GPU with a discreet graphics card, the 3D rendering workload is shared between the two GPUs for a boost in performance. Currently, GeForce Boost is only supported by GeForce 8400 GS and 8500 GT discreet cards, as for the IGP, only the next-gen nForce 700a series of chipsets due to arrive this quarter will be supported initially.

What is CrossFire ?
CrossFire is a high-performance PC Gaming Platform technology that enables multiple ATI Radeon graphics cards and a CrossFire-ready motherboard in a single computer to increase graphics quality and performance.

What is CrossFireX(Quad CrossFire)?
From Techreport.com:
CrossFireX is, quite simply, an extension of the CrossFire dual-GPU feature to three and four GPUs.
Here is a good chart about the cards and motherboards which support CrossFire,CrossFireX and the compatibility list:

What is AMD Hybrid CrossFire?
Hybrid CrossFire allows integrated graphics and low-end discrete graphics to be used in CrossFire mode.

Overall,both Hybrid CrossFire and Hybrid SLI are mainly for power savings and won't give users a great performance boost in games or intensive 3D applications.

Can you use SLI on a CrossFire board or CrossFire on a SLI board ?
Well , in general , the answer is NO;however,there are some methods(like driver hacks) that allows you to do this.
Caution:There is no guarantee that this driver hacks work,so do it at your own risk!

With the release of Core "i" CPUs,Intel announced chipsets(P55,X58,Z68,etc.) that allow users to use CrossFire and SLI on the same motherbard.(However,not all of these chipsets support SLI and Crossfire.Some of them only support one of these MultiGPU options)

Do the cards have to be same model?
For "Most" Nvidia cards the answer is yes,but there are some exceptions too,such as pairing a GTS 250 with a 9800GTX+,which can only be done if both cards have the same amount of memory. (It's possible because GTS 250 is actually a re-badged 9800GTX+)
But again there are some cards like 9800GT and 8800GT which have the same specifications but in general you can't pair them in SLI.(Some users have reported that by flashing a 8800GT's BIOS to a 9800GT's BIOS,you can do it,but its risky and not recommended.)

But for AMD/ATI cards,It's different.
For older models like X1900 cards,you have to use the same/master card in order to run them in CrossFire mode.
But for HD 2xxx cards and up,there are no master cards so you simply can use 2(or more) (same)cards in Crossfire.

You can find more info about mixing cards in SLI/Crossfire down this article(Where the GPU models are)

But what about the memory? Can you SLI 7800GTX 256MB with it's 512MB version ?
For Nvidia cards,the general answer is no.
http://www.slizone.com/object/slizone_ask_mmm013.html
"Another misconception is that the GeForce 7800 GTX (256MB) graphics cards and the GeForce 78000 GTX 512 graphics cards can be paired together. Since these graphics cards use different GPUs, they unfortunately CAN'T be paired together. Always refer the Learn More or Build sections of SLIZone."
So,you generally can't pair a 7800GTX 256 with 7800GTX 512 or GTX 460 768MB with its 1GB version unless you use some 3rd party applications(which isn't recommended).
However,if you manage to run these cards in SLI,then the model,with higher amount of RAM,will reduce it's RAM to match the other card.

For ATI cards,it's different.
As an example,you can Crossfire HD 5870 2GB with it's 1GB version (but again the 2GB version lowers it's memory to 1GB)

What about brands ?
Brands don't matter.It's however recommended that the cards have the same amount of memory and speed.

What happens if the cards have different speed
For ATI cards;
One of the cards will raise/lower its clock speeds to reach the other card's speeds.
For Nvidia cards;
Well it "was" like ATI with older drivers, but with new drivers its quite different.If you use 2(or more) Nvidia cards with different clock speeds in SLI mode,none of them will change their clocks and they will perform at their default clock speed.

A Very important note about CrossFire:
Many users ask to use 1 brige or 2 briges when they want to use 2 cards in CrossFire mode.
The answer is that it will work with 1 bridge without any problems but I recommend using both bridges because:
1_You will never lose either of these bridges.
2_Some users have reported a minimal(not noticeable) performance increase.

Do SLI or CrossFire always improve performance ?
Not always.
There are some games that don't benefit from MultiGPU technology(or require a patch in order to utilize it).
For example,Flight simulator X doesn't benefit from either SLI or CrossFire.
Another example is StarCraft2 which barely benefits from more than 1 card
http://www.tomshardware.com/review [...] 742-8.html

What are SLI and CrossFire certified Motherboards?
SLI certified motherboards:
http://www.slizone.com/object/slizone_build_mobo.html
CrossFire certified Motherboards:
http://ati.amd.com/technology/cros [...] rown1.html

What about RAMs ?
RAM's aren't important for SLI/Crossfire.Just make sure you buy something that's compatible with your CPU and Motherboard.

What are the power requirements for SLI or CrossFire ?
For every configuration,the power requirement is different.
Nvidia cards:
http://www.slizone.com/object/slizone_build_psu.html
AMD/ATI cards:
http://sites.amd.com/us/game/produ [...] plies.aspx

There are some Power Supplies which aren't in the List , but they are compatible , you have to check the manufactures sites too.

Is it really necessary to use SLI or CrossFire ?
It all comes down to 2 factors:
1)The games that you play
2)The resolutions that you play on
As mentioned,there are some games that don't benefit from either SLI or Crossfire;also,I recommend using more than 1 card if you play on resolutions like 1080p or higher because on lower resolutions,you can achieve a great performance with a single card.

Is it better to get 2 mid-range cards or 1 high-end card?
It really depends on you.I myself prefer a single high-end card rather than 2 mid-range cards because usually,the single card produces less heat and has less power consumption but it may cost more too.
So it all comes down to personal preference and budget.

Do SLI or CrossFire double the memory ?
No.Adding another card with more memory doesn't double the overall memory of your cards.

Which is better , SLI or CrossFire ?
It again comes to personal preference and the games that you play.
There are some specific games that scale better under SLI and vice-versa.

A note about Motherboards
For 2-way SLI,motherboards either support CrossFire at dual x16,dual x8 or x16x4 speeds.
The first will give you the best performance.
Dual x8 is also good and performs on par with dual x16 in most games.
But x16x4 is kinda different.
On PCI-E 1.0 boards/cards,there is a huge difference between x16x4 and dual x16(and 8x).
On PCI-E 2.0 boards/cards;however,the performance gap isn't as high.(The performance is notable in some games though,especially on high resolutions)
I personally recommend dual x16 or dual x8 for MultiGPU setups.

Here is a good review which compares CrossFire performance between dual x16,dual x8 and x16x4
http://www.tomshardware.com/review [...] ,2095.html

List of NVIDIA and AMD/ATI MultiGPU compatible Graphic Cards: (All of them are PCI-EXPRESS cards,MutliGPU technology is for PCI-EXPRESS cards not for AGP cards.)

NVIDIA cards(Desktop models)

Geforce GTX 600 Family:
NVIDIA GEFORCE GTX 680

Geforce GTX 500 Family:
NVIDIA GEFORCE GTX 590(1 PCB*)
NVIDIA GEFORCE GTX 580(Supports 3-Way SLI too)
NVIDIA GEFORCE GTX 570(Supprts 3-way SLI too)
NVIDIA GEFORCE GTX 560Ti
NVIDIA GEFORCE GTX 560
NVIDIA GEFORCE GTX 550Ti
NVIDIA GEFORCE GT 520

Geforce 400 Family:
NVIDIA GEFORCE GTX 480(Supports 3-Way and 4-Way SLI too)
NVIDIA GEFORCE GTX 470(Supports 3-Way and 4-Way SLI too)
NVIDIA GEFORCE GTX 465
NVIDIA GEFORCE GTX 460
NVIDIA GEFORCE GTS 450
NVIDIA GEFORCE GT 440
NVIDIA GEFORCE GT 430

Geforce 200 Family:
NVIDIA GEFORCE GTX 295
NVIDIA GEFORCE GTX 285(Supports 3-Way SLI too)
NVIDIA GEFORCE GTX 280 (Supports 3-Way SLI too)
NVIDIA GEFORCE GTX 275(Supports 3-Way SLI too)
NVIDIA GEFORCE GTX 260 Core 216(Supports 3-Way SLI too and also you can it with the Core 192 version.
NVIDIA GEFORCE GTX 260 Core 192 (Supports 3-Way SLI too)
NVIDIA GEFORCE GTX 250(Supports 3-Way SLI too and also you can pair it with 9800GTX+ in SLI configuration,however make sure that both cards have the same amount of memory)

Geforce 9 Family:
NVIDIA GEFORCE 9800GX2 (2 PCB's)
NVIDIA GEFORCE 9800GTX+(Supports 3-Way SLI too and also you can pair it with a Nvidia 9800GTX in SLI configuration,but it's recommended to use the 9800GTX+ card in the first PCI-E 16x slot.)
NVIDIA GEFORCE 9800GTX(Supports 3-Way SLI too)
NVIDIA GEFORCE 9800GT
NVIDIA GEFORCE 9600GT
NVIDIA GEFORCE 9600GSO
NVIDIA GEFORCE 9500GT
NVIDIA GEFORCE 9400GT

Geforce 8 Family:
NVIDIA GEFORCE 8800ULTRA (Supports 3-Way SLI too)
NVIDIA GEFORCE 8800GTX (Supports 3-Way SLI too)
NVIDIA GEFORCE 8800GTS 512
NVIDIA GEFORCE 8800GT
NVIDIA GEFORCE 8800GTS 640
NVIDIA GEFORCE 8800GTS 320
NVIDIA GEFORCE 8800GS
NVIDIA GEFORCE 8600GTS
NVIDIA GEFORCE 8600GT
NVIDIA GEFORCE 8500GT
NVIDIA GEFORCE 8400GS

Geforce 7 Family:
NVIDIA GEFORCE 7950GX2 (2 PCB's)
NVIDIA GEFORCE 7900GTX
NVIDIA GEFORCE 7950GT
NVIDIA GEFORCE 7900GT
NVIDIA GEFORCE 7900GS
NVIDIA GEFORCE 7800GTX 512
NVIDIA GEFORCE 7800GTX 256
NVIDIA GEFORCE 7800GT
NVIDIA GEFORCE 7600GT
NVIDIA GEFORCE 7600GS
NVIDIA GEFORCE 7300GT
NVIDIA GEFORCE 7300GS
NVIDIA GEFORCE 7300LE

Geforce 6 Family:
NVIDIA GEFORCE 6800ULTRA
NVIDIA GEFORCE 6800GT
NVIDIA GEFORCE 6800GS
NVIDIA GEFORCE 6800
NVIDIA GEFORCE 6800LE
NVIDIA GEFORCE 6600GT
NVIDIA GEFORCE 6600
NVIDIA GEFORCE 6600LE

NVIDIA cards(Notebook models)

Geforce 400M Family:
NVIDIA GEFORCE GTX 485M
NVIDIA GEFORCE GTX 480M
NVIDIA GEFORCE GTX 470M
NVIDIA GEFORCE GTX 460M

Geforce 200M Family:
NVIDIA GEFORCE GTX 280M
NVIDIA GEFORCE GTX 260M

Geforce 100M series:
NVIDIA GEFORCE GTS 160M
NVIDIA GEFORCE GTS 150M
NVIDIA GEFORCE GTS 130M

Geforce 9 Family:
NVIDIA GEFORCE 9800MGTX
NVIDIA GEFORCE 9800MGT
NVIDIA GEFORCE 9800MGTS

Geforce 8 Family:
NVIDIA GEFORCE 8800MGTX
NVIDIA GEFORCE 8700MGT
NVIDIA GEFORCE 8600MGT

Geforce 7 Family:
NVIDIA GEFORCE 7950GTX
NVIDIA GEFORCE 7900GTX
NVIDIA GEFORCE 7800GTX

AMD/ATI cards(Desktop models)

AMD/ATI HD 7xxx Family:
AMD/ATI HD 7970
AMD/ATI HD 7950
AMD/ATI HD 7870
AMD/ATI HD 7850
AMD/ATI HD 7770
AMD/ATI HD 7750

AMD/ATI HD 6xxx Family:
AMD/ATI HD 6990(1 PCB)
AMD/ATI HD 6970
AMD/ATI HD 6950
AMD/ATI HD 6870
AMD/ATI HD 6850
AMD/ATI HD 6670
AMD/ATI HD 6570

AMD/ATI HD 5xxx Family:
AMD/ATI HD 5970
AMD/ATI HD 5870 Eyefinity 6 edition(Can be used in CrossFire with the non-Eyefinity 6 version)
AMD/ATI HD 5870
AMD/ATI HD 5850
AMD/ATI HD 5830
AMD/ATI HD 5770
AMD/ATI HD 5750
AMD/ATI HD 5670
AMD/ATI HD 5570
AMD/ATI HD 5550
AMD/ATI HD 5450

AMD/ATI HD 4xxx Family:
AMD/ATI HD 4890
AMD/ATI HD 4870X2(1 PCB)
AMD/ATI HD 4870
AMD/ATI HD 4850
AMD/ATI HD 4830
AMD/ATI HD 4770
AMD/ATI HD 4750
AMD/ATI HD 4670
AMD/ATI HD 4650
AMD/ATI HD 4550
AMD/ATI HD 4350

AMD/ATI HD 3xxx Family:
AMD/ATI HD 3870X2(Read the extra information about HD 5970,its the same for HD 3870X2)
AMD/ATI HD3870
AMD/ATI HD 3850
AMD/ATI HD 3830
AMD/ATI HD 3650
AMD/ATI HD 3470
AMD/AT HD 3450

AMD/ATI HD 2xxx Family:
AMD/ATI HD 2900XT
AMD/ATI HD 2900PRO
AMD/ATI HD 2900GT
AMD/ATI HD 2600XT
AMD/ATI HD 2600 PRO
AMD/ATI HD 2400XT
AMD/ATI HD 2400 PRO

AMD/ATI X19xx Family:
AMD/ATI X1950XTX
AMD/ATI X1950PRO
AMD/ATI X1900XTX
AMD/ATI X1900XT
AMD/ATI X1900GT(Unlike X1900XT and 1900XTX which require a Master card to run in CrossFire,this card can be paired with another X1900GT card)

AMD/ATI X1xxx Family:
AMD/ATI X1800XT
AMD/ATI X1800GTO
AMD/ATI X1800XL
AMD/ATI X1650 PRO
AMD/ATI X1650XT
AMD/ATI X1600XT
AMD/ATI X1600PRO
AMD/ATI X1550
AMD/ATI X1300XT
AMD/ATI X1300PRO
AMD/ATI X1300

AMD/ATI X850 Family:
AMD/ATI X850XT-PE
AMD/ATI X850XT
AMD/ATI X850 PRO

AMD/ATI Cards(Notebook models)

AMD/ATI HD Family

AMD/ATI HH 6xxx Family:
AMD/ATI HD 6970M

AMD/ATI HD 5xx Family:
AMD/ATI HD 5870M

AMD/ATI HD 4xxx Family:
AMD/ATI HD 4870M

AMD/ATI HD 3xxx Family:
AMD/ATI HD 3870M

* PCB stands for Printed Circuit Board, its the hard "plastic-like" colored part in a graphics card/motherboard.

So,I hope reading this guide helps you understand MultiGPU technology better.I've kept this topic opened so that you can ask your questions and post your suggestions about the guide.
Special thanks to emp,4745454b,alias_the_​jester and MouseMonkey for helping me on this guide.

thanks, that was informative.

thanx EMP ,well unfortunately i can only Do QUICK EDIT , when i go to EDIT THIS MESSAGE , it says u are not allowed to edit this message, so i cant change the TOPIC name , but i edited the message , thanx to u

P.S , i know many know about SLI or CrossFire , but because i have seen people making mistake or they have some questions , i decided to make this

thx again

who must i tell to make this thread stickie ?

How did they get the BlackBird from HP to run xfire on a striker extreme board??

Also, you should add in that while it can increase the maximum FPS, it will bring up your minimum FPS, as well, which results in MUCH better gameplay than ANY increase in max. frames (unless the max is under 30 or so.)

i have talked about pairing NVIDIA cards , for CorssFire its the same

to flip_x, its said if u update the graphic card driver, it will be done

how can i tell a moderator to make this stickie ? PM him ?

May I suggest that instead of just saying that "it is usually not worth it", why not point out when it is worth it is worth it and when it is not worth it.

SLI is worth it for me, because I need 2 cards to run 3 monitors, but if I want to run games SLI will let me run them better because of the high resolutions.

Another example is, you got a card that no longer keeps up with the applications you want, and you can get another (maybe used) for cheap on eBay or craiglist.

Anyone selling their GTX cheap? I hear there are much better cards with 3TFlops on the way . I will be happy to take that crappy old GTX off your hands for lets say $200?

Mactronix, sorry if it came across harsh. Definately not my intention, that is why I said "may i suggest" a futher improvement.

Also I do agree with emp's point, that in most cases it is not worth it.

My point is, a lot of n00bs like myself, and hence my suggestion, will want to know when and why it is worth or not worth doing SLI\Crossfire.

I hope they do make it a sticky. it is a very good article.

PS: To the OP, might want to give a heads up to Quad\Tri\Hybrib SLI. I am not sure how reliable the info available is at this point, but did see some posts on them.

Good post. I do not have the money for SLI (or a new anything really) but it was very informative. There were several items that I did not know about(such as the memory not doubling).

i wanted to add information about MB/chipset but i didnt because , i have to talk about the performance difference of 16x16x, 16x4x, 8x8x and thats mostly related to the motherboard section

thx to all for reading this topic, i will PM a moderator now

Sticky!!!

Very good job!

There a few things that need to be cleaned up in the description if it's to remain a sticky.

You need to change the wording of the description of Xfire, you make it sound like ATi copied nV when if anything it's nV who copied ATi and Metabyte's methods of doing multi-card graphics. nV's SLi bears no resemblance to 3Dfx's SLI in anything other than name. And SLi didn't come first in the rebirth, that was Alienware's failed ALX and XGI's volari V8 Duo. And ATi was doing their SIMFusion thing the whole time with Evans & Sutherland.

Also you need to split the solutions up, since your first example of the same cards applies to SLi but not Xfire. So it should be clearly defined which one you're talking about, you examples lets someone guess, but it needs to be explicit.
And in the memory example following it, you talk about memory and then talk about speeds. The 7800GTX is a bad example for memroy since there is athat large difference. But when mentioning memory and talking about size you should mention the size being affected and that they will disable the added memory. You're sort of mixing your ideas here. Then right after that you say you can mix/mathc brands but make sure they have the same memroy and clocks, yet right before that you imply/state they can have different memory/clocks.
For an Xfire section you should add that while the cards need to be the same underlying architecture, they can have different numbers of shaders or pipelines and still work together, like an X1900GT + X1900CF combination.

Also when talking about multi GPU benefits, rememebr to mention that one of the areas of greatest impact is also in the minimum fps, where it will usually increase min fps and smooth out dips into the lower numbers. It's an important factor that's usually missed in the discussion and is the area that would be most noticeable to people not looking simply to push large resolutions or high settings.

And when talking about does it always improve performance, you should also mention that sometimes it actually hurts performance when using the additional card.

When talking about the memory doubling myth you may wish to expand on how the memory is used and why it doesn't 'double the memory' when in Crossfire/SLi mode.

When talking about 2 midrange beating 1 high end, the thing to rememebr is that there are exception to that, like 2 GF7800GTs beating 1 GF7800GTX-512 for less money, or 2 GF8800GTS beating a single GTX or Ultra for the same money, but it depends on the situation, because there's no clear cut rule for that.

I'd get rid of the 'which is better' comment, you could discuss that with intelligent people night and day and never get and answer, and posting to any one benchmark doesn't solve that question either. So I'd pretty much avoid it unless you take the time to explore it further than a link to a single group of tests.

Also I'd avoid posting a list of cards, unless you can keep it up to date and include all the sub cards, better to just link to AMD & nV's list thus the onus is on them and not you.

BTW, what the Crossfire/SLi RAMs sections? Sounds like you're talking about the 'certified' parts. But the way its written sounds like VRAM.

If you're mentioning 'Crossfire/SLi editions' etc. you might want to mention that for AMD the boxes stamped 'Crossfire Edition' come with the ribbon connectors required to run cards in Xfire.

There's also a few spelling mistakes, but I can clean those up directly if you want.

When I referred to midrange SLI vs single high end we refer to 7600GT SLI vs 7800GT(X), not 7800GT SLI vs 7800GTX. At least to me there is High end (Includes, but is not only top of the line), midrange, and low end/mainstream. To me the high end of a graphics card line would be for example ALL 6800 based cards of the Geforce 6 Series (Includes Vanilla, GT, Ultra, GS...), the midrange would be the 6600 series on all it's flavors (Vanilla, GT...), and the low end are 6200 cards, now this can all vary depending on how severely crippled a card is compared to the rest like midrange labeled car dangerously close to being a low end, as far as I know those might be isolated incidents like the 6600LE.

My point is, even if you get SLI 8800GTS over a single GTX you will most likely get better performance on some/most titles but it will not always be the case, however getting 8600GT on SLI to do the job of a 8800GTS will not get you anywhere near close the performance of the aforementioned. (Which is what I was referring on my first post)

about that two mid range cards vs high end card.

if i get to mid range cards work in crossfire, will it give me higher "min" FPS at resolutions 1600x1200 (maybe slightly higher, maybe lower). with high graphics settings?

why im asking, coz ill be buy 2600xt (which is good for budget). n i cant get 8800GTS, nor the new 8800GT (since it will be $200+). n probably in two/three month ill get another 2600xt.

u got me confused there. lol. ill tell u what i understood.

1-two mid range can beat (or may beat) the 8800gts in lower resolution. in higher resolutoin the 8800gts will preveal.
2- but in high resolutions the two mid range will shine

Depending on the resolution and amount of AA the GTX might trump the two cards, because even though you have a lot of horsepower packing on those two cards you only have 320MB of VRam to play with, and that's not a lot.

On top of that you have A LOT more heat and power issues using SLI GTS OC over a single GTX, which in my eyes is not worth the hassle for maybe 5-10 fps more at lower resolutions.

exactly
thanx for helping me in this topic Emp ( u always have helped me )

I just wanted to say thanks for posting this, it just helped me decide which card to purchase

To Zordana
I am glad that it helped u

Power levels definitely more. Not sure about the heat though now that nVidia has a more exhaust style blower HSF. It might actually improve your heat situation with more air being sucked out (and hence in the front) of the PC. The limited input of radiation and conduction likely isn't enough to make that much of a difference over a single card. I've seen more than a few say that their temps went down after adding a second GF8 or HD2K card, which is surprising until you think of the airflow effect.

Yeah the demo is DX10, not sure about the texture quality though. I don't think it'd stress the GTS-320 beyond its limits in SLi, but who knows. Mark Rein talked alot about textures and DX10, so until the final edition comes it's hard to tell, and it could be a big shock for some people guaging their play on this demo.
I like it, but it's defintely less than they were promoting for looks. I don't care about the looks so much as if they have onslaught or not.

So then which would be better?

1.) 2 2900XT 512mb or 1GB in crossfire
or
2.) 1 8800XT or Ultra?

Aside from the extra noise and heat..

Good read Maziar! I am still trying to find a good overclocking MB, but the chipset choices are driving me bonkers in my decision making.
P35
X38
680I...............................

Right, I understand the none multi gpu aspect. Isn't Multi GPU the way most games will go now?

Now are you saying that 2 2900XTs at 512 mb or the ones with 1gb of memory?

Also I wonder if there are any 20 to 24" LCD s with good enough refresh rates to really show off these cards at higher resolutions? Is it 6ms or less that you should be looking for?

Yeah man I read your post..
I was wondering about the memory difference. Like I read in one of your other post saying people need to remember that adding two cards together with 512 me doesnt mean you have 1gb of memory. So I wondered how 1gb would do compared to the 768mb Nvidia cards. Is it just overkill.

Most likely...