ATi's crossfire reviewed

FarFarAway

New member
AnandTech have a great article on ATi's new "SLi" like implentation called: "crossfire".

Cheers go to Balilu who told me about it before I got round to doing my daily "AnandTech check" and for sending me the link!!

Now I'm going to do a brief summary....but the article is long and interesting so take a read!

Whole lot here

ATI have gone a different way about their implentation of multi-GPU rendoring...they have had to...Nvidia released 6months ago and stole the show. The question is: will it live up?



Basics:


Well ATi have releaseed the Radeon Xpress 200 board that gives you 2 x PCI-E x16 ports.

Thanks to AnandTech for the pic:



It seems like a good board but TBH I'm expecting the same initial difficulties as the nforce boards had at first.

When using both GPU's the PCI-E lanes are limited

AnandTech said:
The need to buy a new motherboard in order to upgrade to a multiple GPU solution will likely keep some people from upgrading, but NVIDIA's solutions have the same problem. The fact that CrossFire is only being offered for the X800 and X850 series does limit the upgrade potential at this point. We have been recommending against using multi GPU solutions as an upgrade path option, but offering that freedom is still a plus.

ATI has given us the indication that CrossFire should work on Intel Chipsets as well as their own. This could give new life to those Intel designs originally targeted at SLI. Though not explicitly stating that CrossFire will work in an NVIDIA SLI board, it definitely seems possible. From an adoption/compatibility standpoint, ATI is certainly "evaluating other options".

The silicone

Well ATi have made sense with their GPU pairing. They have said that you can use different cards with different speeds and different BIOS.

It's well worth mentioning that ATi have chosen to limit this to X800 and X850 GPU's....no mid-range cards to compete with nividia's 6600GT (nvidia lead this field to be sure)....which is a bit of a shame IMO.

Pic:



Not sure I like the idea of DVI to DVI to do the sharing, but ATi are the experts....

Also it has to be said that the PCI bus will be limited to x8 for each card when running two. Whether this will be an issue is yet to be seen as no games utilise even half the possible bandwidth yet.

It goes like this:

Both cards rendor what they are sent. The "slave" card then sends all its rendoring information digitally via DVI to the "Crossfire" card and then the shared memory buffer composites the images and sends it to the display.

Technical Pic:



As with nvidia's Sli, the method of rendoring is pre-determined with the drivers....but ATi tend to release more frequently than nvidia so maybe better support there...

Not going to bother you with any more technical gibber....you can read the article for that geeky stuff (ok, ok, ok...I read it!! :o )

Crossfire vs Sli

I can't say it better than here:

AnandTech said:
It doesn't seem plausible to us that ATI has found a way to split the graphics work between two cards in a more compatible way than NVIDIA. But enabling ATI's Super AA modes eliminates the need to split the work. With each card rendering the complete scene (only using different AA sample points) ATI can effectively offer something to all titles where NVIDIA cannot. Those who choose not to enable AA for these titles will likely see a trend similar to NVIDIA's performance: more than one card won't help performance.

So yeah - hope that ATi's solution works as well as it looks like it should!

Performance

Well numbers were pretty vague at this point but they looked fairly good with Doom 3 Ultra looking to be up there in the high 60's with 1600 x 1400 :eek:

And the fact that the cards seem to able to utilise dual display....something nvidia is currently having a problem with....

Conclusions

Well IMHO Crossfire looks very very good. ATi have made it so that their "Super AA mode" can utilise both cards even if proper multi-GPU rendoring will not work. This emans that those who couldn't use AA, will be able to use it...always a nice thing (mmmm...smoooooth lines)

It seems like the chipset lets ATi down, with no SATA II support at all and a buggy Southbridge (there is another alternative - ULI) using ATi's chipset (partners are "encouraged" to use ATi's chipset), it seems nforce is a bit more mature.

name='"AnandTech"' said:
If ATI can get CrossFire out to the market in good volume (for its potential demand), we could have an excellent alternative to SLI on our hands. ATI is also working on licensing CrossFire to SiS, so we may see SiS based boards with CrossFire support early next year as well. Exhaustive performance tests remain to be run, but from a feature standpoint, CrossFire looks good. We would like to see CrossFire offerings for Radeon cards slower than the X800, but other than that we will have to sit back and wait for hardware to draw more conclusions.

All in all, it doesn'tblow SLi out the water....but it puts some big ripples in the pond and looks to be a great alternative to nvidia's SLi....make the choice I spose.

Personally I am going for the more mature Nforce 4 chipset and maybe SLi....but Ati's offering will be well worth taking a look at in the future, especially after it has evolved away from its initial problems.... :)

BIG thanks and creds to AnandTech for a great article :)
 
seems great but i think nvidias sli is still better and will perform better in the futre

with nvidias sli you can you ati cards?
 
limqareb said:
seems great but i think nvidias sli is still better and will perform better in the futre

with nvidias sli you can you ati cards?

ROFL - nvidia's SLi is NVIDIA's SLI - not ATi's!!

No sorry...you have to use 2 x nvidia cards.

I think that ATi's implementation will look very good.... :cool:
 
name='kempez815' said:
It's well worth mentioning that ATi have chosen to limit this to X800 and X850 GPU's....no mid-range cards to compete with nividia's 6600GT (nvidia lead this field to be sure)....which is a bit of a shame IMO.

well it's true that ATI is only allowing x800 and x850 gpus. But IMHO i think 2x6600GT's in SLI is a very STUPID IDEA (IMHO) beacuse why should you buy 2 6600gt's when you can buy one 6800GT which have the same performance and at the same price. and a single 6800gt is worth it to buy than 2x6600gt's because you have less cluttering in the case, less heat and also more overclockabilty and the performance is in all games not like when using SLI.

name='kempez815' said:
Not sure I like the idea of DVI to DVI to do the sharing, but ATi are the experts....

well i also heared that it will be implented so there is loseless quality but still not quite sure about this.
 
Well while I slightly agree about the SLi'd 6600GT's...the idea is that you can buy one now, one later and get the performance of a 6800GT after saving up. Some peeps can't afford a 6800GT straight away. Nividia cater for the mid-range market better than ATi do. :D

Yeah I am slightly amazed at the DVI implimentation....but ATI are the experts and soon the figures will be out and I assume they will speak for themselves.

Basically....SLi or crossfire...whichever you get it will be good. :)
 
I can't stand the external connector idea... I think that's a bit gay, but who knows, I guess it gets the job done!
 
Hexus have managed to get a closer look at a crossfire setup now:



I have ringed in blue the exchange chip that assimilates all the data for the crossfire system to work. Not much of a difference between the cards, but I wonder how much ATi will put on top of ££'s of the card??



As you can see, the master card does not have the rage 3d chip, but the slave does :)



Sweet shot^^



Well that's all from me but once again, the crossfire looks very nice :)

Read the short article at Hexus
 
nvidia uses an internal connector, do all cards have space for the connector or only specialised cards can be used, as i saw the pins are diffirent in the connectors that means that you have to buy both cards at the same time not you buy 1 card 1 time and another separately another time? :o
 
Nvidia SLI: with sli you need to have two vgas which are the same type and same brand ( i.e. both from same manufecturer and same model ) and both have to be sli enabled. you need to have an nforce 4 sli mobo with 2xpci express and then hook them up using the sli bridge which you connect at the top of both vgas. the image is then outputted from the first card installed in the firs pci express slot

ATI Crossfire: with cross fire you need to have two vgas which are of the same category ( i.e. you can't have an x800 with x850 but you can have x800 with x800xl ) and they can be of any brand. one of the vgas mus be a normal vga which people arleady have and the other a master card ( i.e. if someone already owns an x850 pci express he doesn't need to buy one crossfire enabled he just needs to buy another one which is a master card. ). with crossfire there is no internal connectors but the slave card saend data through the special dvi cable which is connected to the master card and then the master cards processes the image created by the salve and the master and outputs them on screen. the special dvi cable can be seen at the picture

hope this helped
 
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