Its been a long time coming but ATI have finally answered the call of Nvidia's SLI with the release of their dual card technology codenamed "Crossfire". Right now we dont have a suitable test rig to bring you figures or results but rest assured when samples are made available we will be bringing you the full rundown. For now Ill go over the information presented to me at a recent meeting and how you should expect Crossfire to improve your gaming experience. At the end of the article ill include an ATI Q&A session which will answer a good selection of questions and act as a reference.

In a nutshell ATI's Crossfire technology allows the end user to utilise two graphics cards to render a single image, this as you would expect will improve performance as each card has less onscreen to render.

As some of you had already expected you will need a new motherboard, this will be based on a new ATI Chipset codenamed RD and RS480, for Amd and Intel solutions. As well as this new motherboard you will need to order a special Crossfire edition graphics card which has the hardware logic to handle this multi GPU technology, the good news is, with this special card you can use your own X850 or X800 card. Older cards are not supported.

As I just mentioned, the compositing logic on the crossfire edition card is the brains of this operation as it handles the distribution of rendering between the two cards. The engine is on an additional chip on the PCB.

The all important part of this equation is how the Crossfire setup handles rendering and ATI have obliged with several "modes" of rendering, the first being "scissor" mode. Scissor rendering is the basic split screen option, and from what I have ascertained this is a simple 50/50 (scissor) cut, but unlike Nvidia's does not appear to have the ability to dynamically monitor and adjust how much each card is actually rendering. Alternative frame rendering is a popular option with Nvidia and the same principal is used with ATI, we have covered this before in articles and have even shown how you can set this up with coolbits on your SLI rig.

The most interesting and talked about rendering mode is Supertiling - a mode unheard of before. With Supertiling, the screen is split up into squares and the two cards alternate rendering the internals of these squares. Each square is only 10's of pixels in width so as you can see this is quite a deep method of rendering. The benefits of Supertiling would be that any intensive object requiring a lot of rendering time will be broken up almost evenly between the graphics cards.

ATI is also bringing with Crossfire new methods of combining anti aliasing with maximum options of up to 14x, however I will be presenting this to you over the coming weeks in a more indepth Catalyst article.

A major benefit with ATI's Crossfire over Nvidia SLI is the fact that Crossfire will not be driver game dependent. Those of you like myself with an SLI setup will be aware that while its improved somewhat in recent months there are still under 100 games supported. Nvidia have made some progress in allowing the end user access to game profiles via coolbits so we can create our own profiles, (ive covered this on the forums before with guides) but it is still touch and go and frequently fails. So for the "average" user, its a case of "cat and mouse", waiting for nvidia to update their detonators with new dual GFX game supporting profiles.

Crossfire eliminates this issue totally and is set to support every game right out of the box. If this works as ATI claim it does, its bound to be one of the biggest selling points ATI will have in their arsenal. After all if you buy two high end video cards in an ideal world you want every game you buy to instantly take advantage of the additional rendering power.

Performance figures have been shown to me, and they look impressive, however until we have the final test boards in our lap with the drivers ATI have finalised I dont feel its a wise move to be showing these. Hopefully within the next 2-3 weeks we can bring you some figures and testing results.

ATI have developed Crossfire with the same connection principals as 3DFX did with the voodoo 2's, with external connectors, this is in stark contrast to the internal bus method implemented by Nvidia. ATI use a proprietary external dongle for this. When I asked ATI why they had chosen this method rather than an internal system, they explained that they felt it was wiser to minimise the need for an end user to reach for internal connections. I also had concerns about image quality as some of you will remember with Voodoo2 in SLi connected via cables some loss of image quality was noticed. ATI have assured me this will not be the case with this configuration - rest assured ill be testing this thoroughly with a Dell 24 inch LCD (2405) at 1920x1200 resolution shortly and reporting the results to our community.

The AMD and Intel chipsets above show HD audio support on the south bridge as well as integrated graphics on the northbridge of the intel variant. The AMD chipset is targeted to gaming enthusiasts so the IGP was removed from the specification list.

As for costs and marketing, there are two crossfire cards announced today, one supporting the X850 series and the other catered for the X800 series. Each Crossfire board should cost around $50 more than the ordinary model. Ok so how does this work?

The X850 Crossfire card is a X850XT GPU with the Crossfire logic onboard, the X800 Crossfire card is a X800XL board with the logic onboard.

According to conversations with ATI the reasons for two different versions of Crossfire is to ensure even load balancing. There are some issues to mention however, if for example you own a 12 pipe X800 pro and purchase a X800 Crossfire card which is a 16 pipe Xxx, the crossfire card will be forced to downgrade itself from 16 pipes to 12 pipes to evenly match the pro board for rendering. Not ideal, but unavoidable.

Below are some Q&A situations that ATI have gathered together to aid understanding of the process, it might prove helpful for those with a specific question.

Q. What is the difference between SLI and CrossFire?
A. The principal differences between nVidia’s SLI system and ATI’s CrossFire are:
-CrossFire can enable multi-GPU rendering on all applications. SLI only works on selected applications identified in nVidia’s driver.
-CrossFire supports more rendering modes than SLI. Supertiling offers good performance and evenly distributes the workload between the two GPUs. CrossFire can use multiple GPUs to improve image quality rather than performance with SuperAA modes. Supertiling and SuperAA modes are only supported on the CrossFire platform, not SLI.
-CrossFire is an open platform that supports multiple chipsets and a wide variety of graphics cards mixed and matched in a single system. SLI systems are constrained to specific chipsets and identical cards.

Q. What graphics cards work with CrossFire?
CrossFire requires a CrossFire Edition graphics card and a standard graphics card from the same series.
The RADEON X850 CrossFire Edition card can be paired with any RADEON X850 graphics card (RADEON X850 PRO, RADEON X850 XT or RADEON X850 XT PE) from ATI or any of its partners including cards previously sold.
The RADEON X800 CrossFire Edition cards can be paired with any RADEON X800 graphics card (RADEON X800, RADEON X800 XL, RADEON X800 PRO, RADEON X800 XT or RADEON X800 XT PE) from ATI or any of its partners including cards previously sold and including the All In Wonder X800.
Because of the backwards compatibility of the platform, there are already almost a million people who are CrossFire-ready.

Q. When will CrossFire graphics cards be available?
A. RADEON X850 CrossFire Edition cards will be in production end of June and available mid-July. RADEON X800 CrossFire Edition cards will be available early August.

Q. Can you use AIW cards in CrossFire?
A. You can use AIW cards in combination with a CrossFire card if they are in the same product family. For example, an All In Wonder X800 can be paired with a Radeon X800 CrossFire Edition card.

Q. What motherboard is required for a CrossFire system?
A. A Radeon Xpress 200 CrossFire Edition motherboard is the optimal platform for CrossFire. CrossFire is also compatible with Intel chipsets that offer multiple x16 physical slots. Chipset support is affected by the level of technical collaboration between the various vendors, and limited quality assurance resources require that we prioritize bringing a particular platform to market.

Q. When will CrossFire motherboards cards be available?
A. Radeon Xpress 200 CrossFire Edition motherboards will be available from our partners beginning in June.

Q. Will CrossFire cards work in an NForce 4 motherboard?
ATI is focused first on qualifying our chipsets with our GPUs. We’ll evaluate Nvidia solutions in the future.

Q. What happens if customers have the wrong combination of products?
A. If a customer incorrectly configures their system they will not see the performance benefits of CrossFire.

Q. When you pair a 12-pipe CrossFire Edition card with a 16-pipe card what happens?
A. To ensure an optimal gaming experience, the two cards will both operate as 12-pipe cards while in CrossFire mode.

Q. When your CrossFire Edition card and your standard Radeon card have different clock speeds what happens?
A. Both cards will continue to operate at their individual clock speeds.

Q Will CrossFire Edition cards work with SurroundView?
A. Yes, the CrossFire platform will work with SurroundView.

Q. What games work with CrossFireTM?
A. CrossFire works with all 3D applications. The end-user is able to run any game with multiple graphics cards cooperatively rendering the images. The end user is able to take advantage of the additional graphics hardware for all games, all the time.
Competitive SLI systems only work on a limited number of games that are profiled in the driver. New games, older games, lesser known games, and even some current popular titles are not supported by SLI, and the end user sees no benefit with this system when running these applications.

Q. Do all games see a benefit with CrossFire?
A. Games that stress the graphics sub-system will benefit most from the additional performance offered by CrossFire. Most new games are designed for advanced graphics, and end users will see large performance increases with multi-GPU systems. Some applications that are more CPU intensive may not scale well with CrossFire. For these applications, CrossFire offers extreme image quality modes that take advantage of the additional graphics power, and improves the overall gaming experience.
Customers using an enthusiast-class motherboard like those based on Radeon Xpress 200 CrossFire Edition motherboards will be able to take most advantage of CrossFire because they are able to get the most performance from their entire system.

Q. Do you need a driver profile for CrossFireTM to work?
No. CrossFire is enabled by default for all 3D applications. With CATALYST A.I. enabled, the preferred rendering mode is selected for targeted applications. For applications that are not identified in CATALYST A.I., or when CATALYST A.I. is disabled, default multi-GPU rendering modes are offered. For applications that are very graphics limited, and can not benefit from multiple high-end graphics processors, the end user has the option to disable multi-GPU rendering completely. In all scenarios the end user has the option to adjust her/his system to best take advantage of multi-GPU rendering.

Q. What is the difference between regular graphics cards and CrossFireTM Edition graphics cards?
CrossFire Edition graphics cards include a “compositing engine” chip on-board. This chip takes the partially rendered image from the standard graphics card, and merges it with the partially rendered image from the CrossFire Edition graphics card. The result is a complete frame rendered at up to twice the performance of a single graphics card. The CrossFire compositing engine is a programmable chip that offers flexible support of different graphics cards, allows a superior feature set (advanced composting modes), and enables further enhancements to be quickly implemented on next generation products. The CrossFire compositing engine also offers a performance benefit to other data transfer techniques, such as peer-to-peer transfers over the PCI-E system bus.

Q. What performance improvement does CrossFireTM bring?
Performance enhancements with CrossFire is application dependent. Performance improvement varies from 1% to 100% performance increase. New, graphics intensive applications will generally see over 80% performance improvement at high resolutions and image quality modes.

Q. How are the two graphics cards connected on a CrossFireTM system?
The two cards are connected by an external cable. The cable is attached from the standard graphics cards’ DVI connector to the CrossFire Edition high density input connector. The partially rendered image is sent through the DVI connection to the CrossFire Edition DMS input connector. The partially rendered image from the cable input is combined with the CrossFire Edition’s partially rendered frame in the compositing engine. The compositing engine combines the result of both cards to output a complete image.

Q. What rendering modes are used when?
A. By default either SuperTiling or Scissor modes are applied. Alternate frame rendering mode is used for applications identified in CATALYST A.I. (when enabled). When CATALYST A.I. is disabled, 16-pipe graphics processors running D3D applications are accelerated by supertiling mode (other configurations are accelerated by scissor mode). Super AA mode is enabled through the control panel.

Q. Can you run Super AA mode in combination with another rendering mode?
A. Users choose either a performance mode (SuperTiling, Scissor or AFR) or Super AA mode. When users are running in SuperTiling Scissor or AFT modes they can use ATI’s existing AA modes (2x, 4x or 6x.)