SLI / CrossFire FAQs

[jtabler]

But doesn't crossfire and SLI have variances in their support for multiple monitors, which would influence the decision to use one or the other? Or is your focus to be whether or not to use a single card or multigpu and not crossfire vs. sli?

 

[Maziar]

Well i know what your are talking about, but i as i said i want to tell about the advantage and disadvantages of both technologies,and the motherboards and other "Inside case" components.

Anyways thanks for your idea

 

[Maziar]

Edited
Now i put both Deskop and Notebook's "MultiGPU Compatible" cards.
For AMD/ATI,there isn't still a card capable of MultiGPU support.

 

[Maziar]

Edited with a new charts and some card updates.

 

[teltra]

hi im new to this but i need some help, i have just bought another evga 8800 gts 640mb acs3 ko edition and ran 3dmark06 (Full version) with a single card i get 9724 but when i sli them i get 9089 thought thats abit strange. here is my rig

e6850 x2 3.0ghz
6gb adata ddr2 800 6400
evga 680i mobo
2x 8800gts ko sli
500gb hdd
coolmaster 650w psu

i thought with sli i should be pushing 12k
the sli is all setup ok

 

[Maziar]

I dont think there is a problem with your system,when you run 3DMARK, you run it in 1280x1024 resolution which barely benefits from SLI,so you can do something else,you can run it with higher resolution like 1680x1050 or 1920x1200 and then you will see it will benefit from SLI.

Also don't worry about 3DMARK so much,run some games and see what will happen,playing games and getting good FPS is more important than 3DMARK.

 

[johnwong1313]

What about 3870,and 3850,how do they work together ?

Can you have more than one 3870 or 3850 when there is a 3870 and 3850 crossfire in your computer?

 

[Maziar]

If you look at the chart at the first page,you will see that HD 3870 can be used in CrossFire with another HD 3870 or HD 3870X2,and HD 3850 can be used in CrossFire only with another HD 3850.

So you can't use HD 3870 with HD 3850 in CrossFire mode.

 

[pauldh]

Actually, with Cat 8.1 and newer, you can mix a 3850 and 3870 in crossfire. If I ever get a crossfire mobo I plan on giving it a try.
http://www.fudzilla.com/index.php?Itemid=40&id=5641&option=com_content&task=view
http://www.cpu3d.com/index.php?option=com_content&task=view&id=3906&Itemid=16&limit=1

BTW, same goes for mixing a 4870 with a 4850.
http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/9159-ati-hd4870-hd4850-crossfire-performance-review-2.html

 

[Maziar]

So why doesnt the chart say that?
http://game.amd.com/us-en/content/images/crossfirex/CF_combo_chart_July08.jpg

 

[pauldh]

The chart is not the clearest in saying it, but I think it does show exactly that. The "." (dot) is what they recommend. But, any combination in a red box will work (and uses the internal crossfire connection). So 2600 pro with 2600xt, 3850 with 3870 or 3870x2, 4850 with 4870, etc.

 

[Maziar]

Oh,i see thanks for that

 

[techgeek276]

I have a Triple SLI Nvidia "SUPER PC" and it's really awesome. Most of the time
I turn off the SLI because I have a Quad Multiple Monitor Display with four LCDs.
During the day, it is my Day Trading Computer, but at night, I crank up that SLI
and hook it into my 60" LG Plasma and play the heck out of some video games!
Man, it makes those graphics so smooth because I have three 512MB GDDR3
Graphics cards that combine into one giant monster video card. Unfortunately, you
can't use multiple monitors when the SLI is on. However, I think they have a
new breed of SLI coming out that can support the multi-monitor function.

 

[Tommar]

I'm free at last!

Great post, thanks! I've been trying to figure out what I need a for a new system, and it was really bumming me out that my motherboard choice was dependent upon whether I wanted to go SLI or Crossfire. Seemed like the tail wagging the dog, but I built my current system 7 or 8 years ago, so what do I know? Other than, if you start out with solid infrastructure, you can get by for 7 or 8 years with only minor upgrades, even for a game machine.

Now I just need to figure out what motherboard to get. Though I still kinda want the Asus Rampage. :/

 

[Maziar]

No problems mate glad you found this useful.
Well what is your budget? what resolution do you play at ?

 

[kylewood_17]

HI. I'm new to the toms hardware forum. sorry if this is the wrong thread to ask this is. Can anyone tell me if the ATI cards on this page are shown for crossfire or if the single cards. i know most of the NVidia cards on this page are SLI but i wasn't sure if the ATI's are or not.

 

[kylewood_17]

oops forgot to paste it.

<a href="http://www.tomshardware.com/charts/gaming-graphics-charts-q3-2008/Sum-of-FPS-Benchmarks-1680x1050-AA,799.html">Tom's Hardware - Benchmark Sum of FPS Benchmarks 1680x1050 AA</a>

 

[Maziar]

Hello and welcome to the forums mate
In that link u posted there are both Single&Dual ATI and Nvidia cards.

 

[kylewood_17]

On the ATI cards, i cant figure out how do tell if they are single or dual.

 

[Maziar]

Example:
ATI X1600(Single)
ATI X1600 CF (Dual)

 

[wwpixel]

Hello
Something's been keeping me up.
I have "ga 965p ds4" MB, with 16x 4x crossfire support.
I was planning to get 4870 1gb card, and then later another one. But your report raised some questions.
16x 4x is NOT recomended you say.
So, should I buy 4870 1gb, and then later when getting another one also change MB? What exactly happens if I push 4870 into 4x pcie?
Should I go with 1gb now and worry about crappy 4x slot later? Or should I save some more juice and just get 4870 X2?
What's the estimated performance difference with two 4870 16x 16x vs 16 4x? I'm handling 42' so prefered resolution is 1920*1080.
Thank you in advance.

 

[Maziar]

Hello and welcome to the forums mate

Well as i said 16x4x mode will kill your CrossFire performance,if u want to get a HD 4870 now and get another one later so you have 2 choices:

1_Change the motherboard to a X38 one when you want to buy the second HD 4870.

2_(Recommended)Instead of gettign 2 HD 4870s get 1 HD 4870X2 which requires one PCI-E 16x slot and keep your motherboard.

The difference is very noticable between 16x4x and dual 16x.

 

[xizel]

hi there

First of all congtatulations on this exellent topic!

for my first question:
On the previous post you recomend X38 board, why not x48 ou even a p45?
I think the X38 is becoming a bit out of date.

My Second question and motive for my reading of this topic:

Im am building a new rig, and after all the investigating i've found out that the 4870 1Gb card is the card to get if you are into 1600 resolution gaming (correct me if im wrong).
The motherboard im eyeing is the Asus P5Q Delux, and i have a doubt about it.
in the specs it says:
2 x PCI Express 2.0 x16 slots, support ATI CrossFireXT technology at x8 link
(PCIe x16_1 blue, PCIe x16_2 black*)
so if i understand well it has 2 16x pci slots, just one thing confuses me, what does the x8 link mean?

And why i want to know this, is because im thinking of the future and so i will probably invest in a second graphics card to pair up with my 4870 1Gb. Also would like to know if its is possible and if it is a good idea do eventualy pair a 4870x2 (that will be much more afordable in like 6 to 8 months) with my 4870 1Gb?
because when i will upgrade my rig it will be with a better 30" or 32" screen beeing able to do much higher resolutions than 1600.

Thanks in advance for any tips or advice.

XiZeL

 

[Maziar]

Thanks mate

About your first question,i recommend X38 over X48 for 2 reasons:
1_The difference between X38 and X48 isn't much
2_X38 is cheaper.
Also X38 is older than P45/X48 but its still a very good chipset.
About P45,well i don't recommend P45 for Dual ATI cards because P45 supports CrossFire at dual 8x mode which sometimes hurts the performance compared to dual 8x mode.

About your second question,ASUS P5Q(P45 series) have 2xPCI-E 16x slot BUT when you want to CrossFire a card then the speed will be dual 8x.
In other words it has 2xPCI-E 16x slot,it means when you have single card it will operate at 16x but when you add another card then both cards will run at 16x.

Yes HD 4870 is good for 1600x1200 gaming,but if you are planing to get a bigger display and CrossFire later,you may want to get a HD 4870X2 instead of HD 4870.

 

[xizel]

Thanks mate

About your second question,ASUS P5Q(P45 series) have 2xPCI-E 16x slot BUT when you want to CrossFire a card then the speed will be dual 8x.
In other words it has 2xPCI-E 16x slot,it means when you have single card it will operate at 16x but when you add another card then both cards will run at 16x.

i think you meant "both cards will run at 8x" ?

maybe i put it wrong but i was asking if it was a good ideal to eventualy pair up a HD4870 with a 4870X2

since now the X2 is much to expensive and maybe in 6 to 8 months would be more affordable.

so for the same price i shoud get a ASUS P5E ?