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Paper Topic:

Competitive Comparisons.

Competitive Comparisons

The main difference between nVidia 's SLI and ATI 's Crossfire can based upon one singular philosophy that both systems attempt to bring a staggering performance improvement , yet both companies have gone about achieving their goal in a very different way (Adams . This will discuss this philosophy by determining the advantages and disadvantages of both of these technologies , and then comparing them as to see which technology concludes as the premier product

nVidia was first to market with its SLI setup and rightfully claims to be the innovator of

dual-GPU systems (Adams , it also remains the cheaper option available to the public with the potential to produce significant performance increases . However , the principle problem that the SLI system processes , is the lack of support it perceives (Young as there is currently the serious issue of limited compatible software Current compatibility lists mention approximately 90 supported software applications , with some of these listed titles seeming to be yet released . This lack of compatibility that the SLI system presents is clearly inadequate , considering the level of investment that the purchase of an SLI system represents thus presenting a major disadvantage to the technology when compared to the support of its rivals , ATI 's Crossfire . ATI claims that its Crossfire product will be compatible with all software , and that , unlike nVidia SLI platform that cannot produce these claims , all applications will receive a performance increase (Adams thus CrossFire obviously holding a major advantage

Both nVidia 's SLI and ATI 's Crossfire use a duel card system (Adams however despite this , each of the systems are far from being identical both in setup and product performance . nVidia 's approach to a dual graphic card system is fairly straightforward , as they assign 50 of the image to each board and then combine the data . One of these cards is responsible for the top half of the image , or item in question , whilst the other manages the bottom half these two products are then combined by a simple u-shaped bridge-connector that links the two cards together The workload doesn 't necessarily have to be 50 /50 but can be re-assigned as the need arises , allowing a depth to the product unlike ATI 's crossfire for example if the top half of the scene requires more processing power than the bottom half , each card will still get half of the work , even if that means splitting the scene 70 /30 (Adams . The SLI technology will also work in an odds and evens way , by splitting scenes into odd and even frames , and assigning each category to one of the cards (Young

ATI 's dual graphics system works on a completely different principle as each CrossFire setup has to have a master card , the Crossfire specific model , and a slave card . These two cards are not connected to each other via a bridge connector , like within the case of SLI , but through a cable , resulting with that the workload division technique of Crossfire being more flexible than nVidia 's technique used upon SLI (Adams . For Crossfire the image can be divided into two halves , i .e top and bottom , or in a 3DFx-like odds and evens way , or into quads , the sub-units in which current graphics processors divide the image to be rendered presenting more flexibility options to the user in relation to SLI , despite nVidia depth of re-setting assignments . The final mode of Crossfire is a picture-enhancing mode , which claims to produce much better picture quality but no real performance gain

Since nVidia and ATI have both invested heavily on creating a dual graphic card system they will want to begin making profit as soon as possible (Adams . Due to this , in to setup SLI and Crossfire , both companies require for the purchase of motherboards that are compatible with their system . nVidia 's SLI requires a motherboard with two x16 PCI Express slots that runs nForce 4 , or an SLI compatible chipset . ATI 's Crossfire also requires motherboards too have two x16 PCI Express slots however the company claims that the boards will need to be running the Radeon Xpress 200 CrossFire chipset . nVidia 's SLI will only work if both of the cards that are used are the same model and SLI compatible this means that for use of the system either two GeForce 6800 Ultras , two GeForce 6800 GTs , or two GeForce 6800s are needed to be present the current SLI range covering all cards from 6600 to 7800 . This is a major disadvantage for SLI as Crossfire is far more flexible as far as graphics cards are concerned , meaning that CrossFire holds a great advantage as it supports the use of different cards provided that one of them is the Crossfire model and will act as the master card . This means that an X850 can be combined with an X800 even though they may feature a different number of pipelines , different clock speeds etc . The one drawback however is that the slowest card will set the pace as the master card will recognize the slave card 's specifications and downshift as required

SLI offers two different rendering modes , Alternate Frame Rendering (AFR ) and Split Frame Rendering (SFR (Adams . SFR is the most commonly used and works by splitting the screen in two horizontal portions , each rendered by a different card . If the driver determines the load is just too much for one card to handle , it changes the position of the separating line to balance the load . As a result , SLI benchmarks report quite steady frame rates , which are very consistent in increasing resolution or enabling image quality options like Anti-Aliasing and Anisotropic Filtering . This may seem like an advantage of SLI withholds over Crossfire however it is actually a disadvantage as , upon Crossfire 's rendering capabilities far surpass what SLI has to offer ATI 's Crossfire offers four kinds of rendering modes for use , which are AFR , Supertile , Scissor and SuperAA . AFR works by rendering all odd frames with one GPU while all even are left to the other , which is basically based upon the exactly same principles used within SFR , used by nVidia (Adams . The main problem with this method is that if a frame contains data that affects the rendering of the next frame to come , then that data needs to be transferred between the two cards , due to this reason

While both company 's solutions are appealing , they are both plagued by a variety of issues . The cost of CrossFire makes it a distant dream for most members of society , as the cost of the expensive CrossFire compatible card , the motherboard and the slave board , and an appropriate processor will reach nightmarish proportions . ATI 's Crossfire offers a dual-GPU system with a variety of rendering modes that supports both OpenGL and Direct3D games and applications , with its rendering capabilities holding slight superior capabilities its flexibility also extends to the cards that can be used with the system which do not have to be identical . Due to this , I perceive ATI 's Crossfire to be greater than SLI

Works Cited

Adams , Edward G . - Crossfire Vs . SLI ' - Wired Magazine - 21 /07 /2005 - Page 37

Young , Michael J . - So You Want A nVidia ' - Technolmagic - 10 /080 /2005 - Page 5


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