This thread is so big, the answer to my question may already be answered, so I apologize if this is a repeat question.
I am currently in the process of ordering parts for building my own computer. I would like to use Crossfire-X to link two graphics cards to use together, but the cards I have picked lack the typical connector for the bridge on the top of the cards.
My reason for wanting to Crossfire these cards is to support three (3) monitors. I know that I do not have to Crossfire them to support the three monitors, but I would like to try it so if I ever need to link two graphics cards in the future I will have the experience.
I want to know if these cards do not need the bridge in order to function in Crossfire-X? I have found some info that says that lower end cards do not need the bridge because the PCIe bus has the bandwidth now to support the Crossfire-X technology without the bridge, unlike previous versions of the PCIe bus.
i tried once tow ati 4850 512mb in cross fire mode with core i7-920 as toms hardware recommended, it was horrible experience because 1)you cant max-out games graphics details because you are limited to 512mb frame buffer 2) almost all ati 4850 was equipped with very bad cooling system and weren't designed for crossfire ,one 4850 on its own go as hot as 94c, and when you play on CF mode it reach 107c and when that happen the games slow down, and you also need to update the drivers every month with every new game to make sure that both cards are working(without latest drivers some new games wont work on CF mode) after that i will never try CF OR SLI again
I set up 2 6870 cards in crossfire and my games FPS sat at 60 on high settings (MW3, BF3) but I was lagging for some reason. Took the second card out and stopped lagging. So sometimes Crossfire does affect performance.
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.
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 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 ?
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/reviews/crossfire-sli-scaling,2742-8.html
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.
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
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 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 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 X850 Family:
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 Maziar: Very informative, lucid, comprehensive and easily understood. Answered my question, saving me the trouble of posting it.
XFX Radeon HD 7970 black is compatible with the other in its range HD 7970 for CF?
seems your saying that as long as the GDDR is same and the speed is aits full steam ahead ? am i right ?...and how will this play out for the OC on the black edition ?
if this has already been addressed I am sorry.. I just need some help now..
I have a problem.. I have 600 bucks worth of cards and they don't perform.. I have two MSI N560GTX-Ti Twin Frozr II 2GD5/OC.. with 2GB.. I have a i-7 2600K CPU and a GIGABYTE GA-Z68XP-UD3 motherboard.. Running 16 GB Ram (2X Crucial Ballistix Sport 8GB. I also am running two Chronos SSD as well as 2 1 TB WD sata 6 drives.. I have a 680 watt APEVIA ATX-AS680W-BL 680W.
I can run one card and it crushes the two in SLI.. Can anyone tell me why? Seems afterburner telles me second card has 0% GPU use..