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 CrossFire ?
Its like SLI , but its for AMD/ATI GPUs.
Can you use SLI on a CrossFire board or can you use CrossFire on a SLI board ?
Well , in general , the answer is NO. But it's said that if you hack the drivers , you can use SLI on a CrossFire board or CrossFire on a SLI board
Do the card have to be same model?
I answer it with an example:
You have a NVIDIA Geforce 7800GTX 256, and you want to add another card , the second card has to be 7800GTX exactly.
But what about the memory? Can you add a 7800GTX 512 and use that with 7800GTX 256?
It's recommended to use a 7800GTX 256 with a 7800GTX 256 and 7800GTX 512 with 7800GTX 512.
BUT you can use a 7800GTX 256 with 7800GTX 512 , BUT the 7800GTX 512 will lower its clock to operate with the 256 one , so it wont have its true power. (This option isn't recommended )
What about brands ?
Well the brand doesnt matter , again for example , you can use XFX card with EVGA card , or SAPPHIRE card with
DIAMOND card , just make sure they have the same memory and same clocks.
Caution! If you use 2 exact same card with same amount of memory , but one of the has higher clocks than the other one , then the card with higher clocks will reduce its clock to reach the other card
Do SLI or CrossFire always improve performance ?
Not Always , there are some games that dont take advantage of SLI or CrossFire , so you wont see a difference between 2 cards and 1 card in those games , but in games that take advantage of SLI or CrossFire , 2 cards will perform better than one.
What are SLI or CrossFire certified Motherboards:
For SLI certified Motherboards ,go here :
http://www.slizone.com/object/slizone_build_mobo.html
For CrossFire certified Motherboards go here:
http://ati.amd.com/technology/cros [...] rown1.html
WARNING: Some RAMs have SLI or CrossFire logo on them. Many people ask if they are the only RAMs which support SLI or Crossfire.
Well thats wrong , there are many RAMs which dont have SLI or CrossFire logo but you can use SLI or CrossFire with them without any problem.
What are the power requirements for SLI or CrossFire ?
For each card , the Power requirement is different , if you want to know if your Power Supply can handle SLI or CrossFire , check here
For NVIDIA cards, go here:
http://www.slizone.com/object/slizone_build_psu.html
WARNING: Therer are some Power Supplies which aren't in the List , but they are compatible , you have to check the manufactures sites too
And for CrossFire cards , go here :
http://ati.amd.com/technology/cros [...] rown2.html
Is it really necessary to use SLI or CrossFire ?
Well , it really depends mostly on the resolutions and games you play , resolutions like 1920x1200 and higher benefit more from SLI or CrossFire than resolutions like 1600x1200 or lower (I dont mean SLI or CrossFire wont be good for resolutions like 1600x1200 or lower , i am just saying that SLI or CrossFire shines in higher resolutions .
Also as i said , it depends on what games (with what settings) you play , for example if you just want to play games at good settings (with not everything at maximum settings) then MultiGPU technology isn't needed , but if you want to play with every option at maximum settings, then SLI would help , but again i repeat , resolution is very important.
Caution: Due to some problems (like Drivers and etc) in some games, a single card (like X1900XT) may beat 2 1900XT in CrossFire mode! so dont always think that 2 cards will beat one card.
Should i get 2 midrange cards instead of one high-end card ?
No, again i will answer this with example. 2 8600GT or single 8800gts ? this on of the most common questions in forums. single 8800GTS (320 or 640) will beat 2 8600GT in games , because a single 8800GTS has more stream processors , more memory clock , more bandwidth. so again 1 single high-end card will beat 2 midrange cards.
Should i get 2 High-End cards or one Ultra-High-end ?
This is again one of the most asked questions. (The time i am writing this guide , The best NVIDIA cards are 8800GTX and 8800 ULTRA). Many ask that 2 8800GTS 320 will cost like a single 8800GTX 768, which is a better buy?
Well, in some cases , 2 8800GTS 320 cards will beat a 8800GTX cards(Mostly in games that dont need high memory and also in games that benefit MultiGPU technlogy). But in some other games (Mostly the games that need more memory to run better) a 8800GTX beats 2 8800GTS 320 in SLI mode.
Also remember that 2 8800GTS 320 cards will be more noisier and also they will produce more heat than one single 8800GTX.
Do SLI or CrossFire double the memory ?
This is one the questions that many people make mistake understanding it .
The answer is NO , SLI or CrossFire doesnt double the memory , You have a 512MB card , adding another card wont make your memory 1GB, it still will be 512MB
Another example :
A game needs 512MB card to run at maximum settings , and you have a 256MB card , and you think if you add another 256MB card , your memory will be 512MB and thats not true.
You may see this mistake in many sites.
Which is better , SLI or CrossFire ?
Well , you cant say exactly which is better , in some games SLI does better than CrossFire and in some games CorssFire does better than SLI, for benchmarks and tests , go to Tomshardware charts:
http://www23.tomshardware.com/graphics_sli2007.html
List of NVIDIA and AMD/ATI CrossFire compatible Graphic Card: (All of them are PCI-EXPRESS cards)
NVIDI cards
Geforce 8 family :
NVIDIA GEFORCE 8800ULTRA
NVIDIA GEFORCE 8800GTX
NVIDIA GEFORCE 8800GTS 640
NVIDIA GEFORCE 8800GTS 320
NVIDIA GEFORCE 8600GTS
NVIDIA GEFORCE 8600GT
NVIDIA GEFORCE 8500GT
Geforce 7 Family:
NVIDIA GEFORCE 7950GX2
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
AMD/ATI cards:
AMD/ATI HD Cards:
AMD/ATI HD 2900XT
AMD/ATI HD 2900PRO
AMD/ATI HD 2600XT
AMD/ATI HD 2600 PRO
AMD/ATI HD 2400XT
AMD/ATI HD 2400 PRO
AMD/ATI X195O Family:
AMD/ATI X1950XTX
AMD/ATI X1950PRO
AMD/ATI X1900 Family:
AMD/ATI X1900XTX
AMD/ATI X1900XT
AMD/ATI X1900GT
AMD/ATI X1800 Family:
AMD/ATI X1800XT
AMD/ATI X1800GTO
AMD/ATI X1800XL
AMD/ATI X1650 Family:
AMD/ATI X1650 PRO
AMD/ATI X1650XT
AMD/ATI X1600 Family:
AMD/ATI X1600XT
AMD/ATI X1600PRO
AMD/ATI X1550 Family:
AMD/ATI X1550
AMD/ATI X1300 Family:
AMD/ATI X1300XT
AMD/ATI X1300PRO
AMD/ATI X1300
AMD/ATI X850 Family:
AMD/ATI X850XT-PE
AMD/ATI X850XT
AMD/ATI X850 PRO
Warning: AMD/ATI cards need a CrossFire edition of its model to run at CrossFire mode (With the exception od AMD/ATI HD series)
from :
http://www.tomshardware.com/forum/24...crossfire-faqs
Of Sli and Crossfires
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