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
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!!
)
Crossfire vs Sli
I can't say it better than here:
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
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.
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
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!!

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

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
