SLI / CrossFire FAQs

Hello all THG forum users , i have seen many of my friends in this forum making mistakes about SLI/CrossFire technology and also there are many questions about it in here , so i have decided to write a guide that helps you undertand these technologies better , so lets 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 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)?
I found a very good definition for it in 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?
Its a technology from AMD which allows an integrated graphics and low-end discrete graphics in CrossFire mode.
You are basically taking two very slow GPUs and making one not-so-slow GPU.
This can only be done with AMD chipsets and AMD/ATI Graphics.

Lets simply say that both Hybrid CrossFire and Hybrid SLI are mainly for power savings and won't give users a great performance boost.

What is Nvidia Hybrid SLI?
I found a very good information in Hothardware.com and here is it:
NVIDIA's Hybrid SLI technology gives users the abilty to pair an IGP, or mGPU (motherboard GPU), with a discreet graphics card, or cards, for two new mdoes 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.

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.
Caution:There is no guarantee that if you hack the drivers then you use SLI on a CrossFire Motherboard or CrossFire on a SLI board, so do it at your own risk!

However,with the release of i7/i5,Intel announced twe new chipsets which are X58 and P55 that allow users to use CrossFire and SLI on the same motherbard.(However X58/P55 boards support only CrossFire,some only support SLI and some support both,so if you wanted to buy a new motherboard,make sure you check this first.

Do the cards have to be same model?
For "Most" Nvidia cards the answer is yes,but there are some exceptions too like pairing a GTS 250 with a 9800GTX+,which can be done since the
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.
I wrote about the cards which have different names but can be used in SLI mode in the "Model's section" down this post,other than those all other cards must be same model in order to run in SLI mode.
but about AMD/ATI models,for models like X1900 series and lower you have to use the same/master card to use CrossFire but for HD 2xxx series and up,check the compatibility chart on top of this post.
For Nvidia cards,here is 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.
However you can use a 7800GTX 256 with 7800GTX 512 , BUT the 7800GTX 512 will lower its RAM to 256MB to operate with the other card, 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 a XFX card with a EVGA card , or a SAPPHIRE card with a DIAMOND card , just make sure they have the same memory and same clocks.

What will happend if 2 cards have the same amount of memory but one has higher clocks than the other?
One of the best ways to learn is to make examples.
You have a 8800GT(Normal edition,no OverClocks) and you want to add another 8800GT(Which is OverClocked),then:

1_The OverClocked one will lower its clocks to reach the Non-OverClocked card.

2_You can OverClock your card(The one that has Stock frequencies) and reach the OverClocked card.
Remember, you cant ALWAYS OverClock the normal card to reach the other card,because it may not OverClock that much and may become unstable.

WARNING:There are many exceptions in Computer Hardware, for example "Mousemonkey" a member of this forum has told me that when he puts his ASUS 7900GT card (Which is at stock speeds) with a XFX 7900GT(A OverClocked card) the ASUS one raise its clock to reach the XFX one which is an exception and as i said exceptions are alot in Computer Hardware.

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 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 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: There 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.)
This(MultiGPU technology) has been more optimized though and has become more mature than before, i mean in the first years of MiltiGPU technology the drivers werent as good as they are now and also not all games took advantage from MultiGPU, but things have gotten better(but not the best, because there are still games that dont take advantage MultiGPU like Flight Simluator X and there are still lots of driver problems too.)So in some of today games that really drain a lot of power from GPU, MultiGPU performs good at low resolutions (again in some games).
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 alot.
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.

Some games like FLIGHT SIMULATOR X are mostly CPU-limited rather than GPU-limited:
http://www23.tomshardware.com/grap [...] &chart=293

8800GTX VS 8800GTX in SLI :

8800GTX:
1920x1200 : 22.6
1600x1200 : 22.4
1280x1024 : 23.0

8800GTX in SLI:
1920x1200 : 22.6
1600x1200 : 22.4
1280x1024 : 23.0

But here is an example of a game which benefits from SLI like OBLIVION:

8800GTX VS 8800GTX in SLI :

8800GTX:
1920x1200 : 28.7
1600x1200 : 32.5
1280x1024 : 43.6

8800GTX in SLI:
1920x1200 : 53.8
1600x1200 : 61.2
1280x1024 : 77.1

So is it better to get 2 mid-range cards or 1 high-end card?
I answer this with an example,lets say we want to compare 2 AMD/ATI HD 4770's with 1 AMD/ATI HD 4870,well in games that benefit from MultiGPU,2 HD 4770's would win but there are some exceptions too,for example some games doesn't benefit from MultiGPU(Which i talked about this)and in those situations the faster card takes the lead.

Also many ask that whether to get 2 HD 4870's in CrossFire or 1 HD 4870X2(I mean getting 2 cards and use them in CrossFire/SLI or get a single card which has the power of 2 cards)
Well by looking at the benchmarks you will find out that actually 1 HD 4870X2 is faster than 2 HD 4870's by 0-15% in "MOST" games(there are some exceptions too that 2 HD 4870's take the lead)also 1 HD 4870X2 doesn't need a MultiGPU Capable motherboard and it produces less heat and has lower power consumption too.

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,so both cards will use 512MB of RAMs but the memory won't double.
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://www.tomshardware.com/charts [...] ,1468.html

A note about Motherboards:

Some Motherboards support Multi-GPU Technology at Dual 16x mode, some support it at Dual 8x mode and some support it at 16x 4x mode Etc, what are the differences?
Well for getting the best performance out of Multi-GPU cards,you need a Motherboard that supports Multi-GPU at dual(Or more) 16x mode like Nvidia 790i ULTRA SLI, Nvidia790i SLI, Nvidia 780i SLI, Nvidia 680i( As i said, NVIDIA 790i ULTRA SLI ,790i SLI ,780i SLI and 680i SLI support 3-Way SLI too(Nvidia 680i LT SLI chipset has 2 PCI-E 16x slot which supports 2-way SLI only.),Nvidia 590i SLI, Nvidia nForce4 SLI 16x, ATI CrossFire Xpress 3200,Intel X38,X48 and X58.

Dual 8x is a very good configuration too,it doesn't have alot of difference(performance wise) with Dual 16x and its cheaper too.
Chipests like Intel P55*,Intel P45 Nvidia 750i SLI, Nvidia 650i SLI,NVIDIA 570i SLI, NVIDIA nForce4 SLI, ATI Radeon Xpress 200, Intel 975x and ONLY few Intel P35 boards(Like ASUS BLITZ FORMULA and ASUS BLITZ EXTREME) support Multi-GPU at dual 8x mode.

However,there are some expections too,for example EVGA has a 750i Motherboard(The model of it is
EVGA 750i SLI FTW)Which supports SLI at dual 16x mode unlike many 750i Motherboards which support SLI at dual 8x mode.

The last one is 16x 4x, this one is the weakest and doesn't perform very good compared to dual 8x or dual 16x,so i won't recommend it for Multi-GPU configuration. Intel P35 and P965 chipsets support Multi-GPU at 16x 4x mode.

Here is a good review which compares CrossFire performance between dual 16x,dual 8x and 16x 4x:
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 APG cards.)

NVIDIA cards(Desktop models)

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 SLI this card with normal GTX 260 too,
NVIDIA GEFORCE GTX 260 (Supports 3-Way SLI too)
NVIDIA GEFORCE GTX 250(Supports 3-Way SLI too and also you can pair this card with a 9800GTX+ in SLI configuration,however make sure that both cards have the same amount of memory)

Geforce 9 Family:
NVIDIA GEFORCE 9800GX2(Read the note about the 7950GX2,its the same for 9800GX2)
NVIDIA GEFORCE 9800GTX+(Supports 3-Way SLI too)
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(Remember, you may think that because 7950GX2 is actually "2 cards attached to one" then you need a SLI motherboard to use it, but you dont, for single 7950GX2, u will need just one PCI-E 16x slot.
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 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 58xx series:
AMD/ATI HD 5970(Warning:The HD 5970 is NOT 2 cards (like Nvidia 9800GX2).Its actually 2 GPUs on one card and it has 1 PCB** compared to 2 PCBs of 9800GX2,so you "Don't" need a CrossFire board to use this card,it requires only one slot.)
AMD/ATI HD 5870
AMD/ATI HD 5850
AMD/ATI HD 5770
AMD/ATI HD 5750
AMD/ATI HD 5670
AMD/ATI HD 5570
AMD/ATI HD 5450

AMD/ATI HD 48xx series:
AMD/ATI HD 4890
AMD/ATI HD 4870X2(Read the extra information about HD 5970,its the same for HD 4870X2)
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 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 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 X195O Family:
AMD/ATI X1950XTX
AMD/ATI X1950PRO

AMD/ATI X1900 Family:
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)

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

AMD/ATI Cards(Notebook models)

AMD/ATI HD family:
AMD/ATI HD 4870
AMD/ATI HD 4850
AMD/ATI HD 3870
AMD/ATI HD 3850

*:Most of Intel P55 chipset motherboards support CrossFire at dual 8x mode but there are some exceptions too which support CrossFire at 16x 4x mode.
http://www.intel.com/products/desk [...] erview.htm

PCI Express 2.0 interface :
Offers up to 2.5GT/s for fast access to peripheral devices and networking with up to 8 PCI Express* 2.0 x1 ports, configurable as x2 and x4 depending on motherboard designs.

**: emp and 4745454b (They are good friends of mine in this forum who help me very much and i thank them for their help)gave me a good definiton and explanation of PCB to me: PCB stands for Printed Circuit Board, its the hard "plastic-like" colored part in a graphics card/motherboard.

9800GX2 has 2 PCBs so its actually 2 cards attached to one.But HD 3870X2 has 1 PCB and its actually 2 GPUs on card which has the power of 2 HD 3870s.

Warning: AMD/ATI X1800/X1900/X1950 cards need a CrossFire-Edition of them to run in CrossFire mode.But for HD Family its different, they don't need CrossFire-Edition, they just cant work with each other for example a HD 2600 works with another HD 2600 just fine.
Also please read the note about CrossFireX at the first parts of this guide.

If you found something wrong in this guide please tell me to fix it,also i thank all who helped me in this topic.
Also if you have seen that i have put a link from other site,its because that it had a very good information about MULTI-GPU technology.

So i hope reading this guide will help you understanding MultiGPU technology better , if you have any question, simply ask and i am glad to answer

^ glad u liked it
dare i say : "plz make it sticky ?"

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.