SLI / CrossFire FAQs

[Maziar]

And here is the final answer:
http://www.anandtech.com/video/showdoc.aspx?i=3209

AMD is the first out of the gates with the Radeon HD 3870 X2, based on what AMD is calling its R680 GPU. Despite the codename, the product name tells the entire story: the Radeon HD 3870 X2 is made up of two 3870s on a single card.

 

[4745454b]

Let me fix the quote for you.

AMD is the first out of the gates with the Radeon HD 3870 X2, based on what AMD is calling its R680 GPU. Despite the codename, the product name tells the entire story: the Radeon HD 3870 X2 is made up of two 3870 GPUs on a single card.

The 9800GX2 is two PCBs facing each other, bleeding heat into the same heatsink, with a fan running air over it for cooling. Each PCB has a single GPU on it. The 3870x2 is a single PCB, with two GPUs on them. The one in the back has an aluminum cooler, with the GPU in the front has a copper one. It does indeed have two 3870s on it, but they are facing the same direction, on the same PCB. If you count "cards" based off of the number of PCBs, then the 9800GX2 is a dual card, while the 3870x2 is not.

 

[Maziar]

If the things u say are true then why it says its actually 2 HD 3870 on a single card and also why in the tests when they use 2 HD 3870X2 then they call it QUAD-CROSSFIRE?

 

[nukemaster]

I do not count PCB's as a card each.

By that logic QuadFX was a quad core just like intels(and not 2 dual cores with all the downfalls people mentioned....even intel is 2 x dual cores anyway). since it was on the same board with 2 sockets and 2 memory controllers.

the X2 and GX2's do the same thing with one or two boards they still have 2 full cards(minus the video outputs..). And thats the limit since each card has to have its own memory....imagine if they could have 1gig and both cards could use it(like how core2 has a shared cache. now that would be a dual core gpu and not two cards slapped together). As it stands now, high res and high AA do effect the small 512megabyte buffer.

Just my 2 cents

 

[4745454b]

@Maz, because they are counting the GPUs like you are. Two 3870x2 in CF would be four 3870 GPUs, hence "quadfire". As I said, its all how your count. PCBs, you have two. GPUs, you have four.

@nuke, actually you might have just proved my point.

the X2 and GX2's do the same thing with one or two boards they still have 2 full cards(minus the video outputs..)

The x2 only has the three standard outputs that all video cards have. The 9800GX2 however has four, two for each card. Go read some reviews and figure out whats underneath those heatsinks. Obviously you guys aren't understanding/believing me.

3870x2 http://www.newegg.com/Product/Product.aspx?Item=N82E16814121228
9800GX2 http://www.newegg.com/Product/Product.aspx?Item=N82E16814500026

 

[Maziar]

I think i got what u are saying
u are saying 9800GX2 has 2 PCB so its actually 2 cards
HD 3870X2 has one PCB so its one card
right ?

and the reason anandtech says its 2 HD 3870 is..........?

 

[Maziar]

so ?

 

[nukemaster]

The x2 only has the three standard outputs that all video cards have. The 9800GX2 however has four, two for each card. Go read some reviews and figure out whats underneath those heatsinks. Obviously you guys aren't understanding/believing me.

3870x2 http://www.newegg.com/Product/Product.aspx?Item=N82E16814121228
9800GX2 http://www.newegg.com/Product/Product.aspx?Item=N82E16814500026

I only see 3 outputs 2 dvi and one hdmi, but for all i know the DVI and HDMI are linked(like on many dvi/hdmi onboard cards)....

Either way its not 4 so

I know EXACTLY whats under the heatsinks....2 cards on one pcb(ATI) and 2 cards on 2 pcbs. Either way the lack of Svid for SD tv users on the 9800GX2 SUCKS.....

Look X2 with 4 video outputs
http://www.techspot.com/review/86-ati-radeon-hd-3870-x2/

 

[4745454b]

The reason Anand says it is two is because there are two GPUs, and you are already using one of the CF links. When you say card, I am old school and picture the PCB. Its a bit like saying the C2Ds is two CPUs. It's two cores, on one PCB. I don't see how this is any different.

@nuke, I was referring to the only pic of the 9800GX2 that I've seen. Looking back at it, it is the 2 DVI ports, one DMI, and the fourth that I saw is probably an optical out for audio. Tell me what you think it is.

http://www.tomshardware.com/2008/01/05/exclusive_nvidia_geforce_9800gx2/

 

[Maziar]

ok thanks mate

 

[Maziar]

Well its not still in NVIDIA site, but i will put in the FAQ as soon as it comes out
thanks

 

[nukemaster]

I would almost call a PD and core2 Quad 2 cores(well 2 dies) on one pcb(substraight).

Anyway, there is not point in auguring about this. Its a video card....good enough....

Oddly they appear to have dropped the optical port. Any clue if Nvidia even has an onboard sound card for HDMI or could the optical have been an input for HDMI pass through?(warning wild ass guess!!!)

A quick google shows this may be true...

http://ketzone.com/blog/?p=152

Maybe it was dropped because people thought it was an output when in fact its just an input for the HDMI port.

 

[bliq]

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

HP worked with Asus and modified the chipset. It's not a stock striker extreme. And HP has the money, resources, and engineering muscle to do that.

 

[Maziar]

Edited with lots of thanks to emp and 4745454b who helped alot about
HD 3870X2 and 9800GX2 architecture

 

[TuVNeRa]

I cannot make crossfire with PowerColor 1GB HD3870 X2
My motherboard is GIGABYTE P35-DQ6. I have already upgraded latest bios from Gigabyte web server. I tried both Vista 32bit and Vista 64bit.

What is the wrong with it?

 

[4745454b]

If I'm reading everything right, there is no problem. If you have one 3870x2, you can't/don't need to enable CF. The CF link is made internally on the card, its invisible to the user. This also allows you to use the 3870x2 on non CF boards, either single slot or Nvidia chipset motherboards. You would need two 3870x2 to enable CF, which I don't see in your device manager. (you have two 3870x2's listed, but you should get one listing for each DVI port. Thats at least how it works with my older x1800xt.)

Anyone feel free to correct me if I'm wrong.

 

[TuVNeRa]

I have only 1 3870 X2
But a moderator from another forum has told me CF menu must be shown in Catalyst Control Center and there must be shown on device manager like this:

 

[blotch]

You may want to include something about the stability of 1 card vs multiple cards. Moving from one 1600xt to 2 and when moving from one 3870xt to 2, I started having some stability problems.
Also I love my crossfire setups but when i moved from 2 1600xt's to a 1900xt it was an insane improvement. I know that there are lots of reasons for the difference but even though adding more cards to a system will improve performance I still like the idea of the single "Monolithic" card like mine was for me or how the 8800GTX was for a long time.
I got excited when the 1GB-512bit 2900xt's came out, until they sucked. I hope ATI tries that again with these newer/multi cores to make crossfire more effective. I think even 1gb-256bit may work with PCI-E 2.0 but I wouldnt know if a 256bit bus is wide enough for a Gig of GDDR3/4.
Anywho nice post.

 

[TuVNeRa]

I think, I' ve solved the problem.
Because of Vista 64bit drivers do not work properly.
This screen shot is from Vista 32bit:

 

[4745454b]

What version of windows are you using?

 

[Maziar]

I think he said VISTA 32bit
But its strange it should be right in both VISTA 64 and 32 not only 32

 

[vincegreg]

Im planning on buying a computer which has 4 gb of ram and a 2.4 ghz quad processor. I have the choice of getting a single 768 mb 8800 gtx nvidia graphics card or a Dual nvidia 8800 GT 512MB. Which is better?????

 

[vincegreg]

Im planning on buying a computer which has 4 gb of ram and a 2.4 ghz quad processor. I have the choice of getting a single 768 mb 8800 gtx nvidia graphics card or a Dual nvidia 8800 GT 512MB. Which is better?????

 

[Maziar]

What resolution do you play at ?

 

[fast_furious]

hi, i've got a quad core and a asus p5k E wifi, crossfire, and i've read in a before post that is possible in some boards to make corssfire boards into SLI boards, can this Asus P5K E WIFI be done that ? i've got a XFX GTS 8800 640 MB graphic and wan't to know if i can get another GTS SLI mode

THX