ATI's X8xx CrossFire Graphics Arrive
by Derek Wilson on September 26, 2005 1:00 PM EST- Posted in
- GPUs
Super AA and CrossFire
By rendering the same frame on both cards with different subpixel sample patterns, the images can be blended together to provide a smoother image at any given resolution than a single card is capable of rendering. At the same time, as resolution increases and pixel size decreases, antialiasing becomes less important. This is yet more support for believing that greater than 1600x1200 resolutions should be supported on a high end setup like this.For those who will be running CrossFire solutions at 1280x1024 or even 1600x1200, Super AA will be a welcome addition to image quality. ATI already leads the industry in AA quality because they use a programmable sample pattern when antialiasing a pixel while NVIDIA uses a fixed ordered grid approach. The difference really starts to add up when SLI AA and Super AA are compared.
From left to right, 4xAA, 8xSLI AA/10xSuper AA, 16xSLI AA/14xSuperAA. ATI is the top row.
The more even spread that ATI is able to maintain over a single pixel gives the CrossFire solution a better result. Even though NVIDIA's 16x SLI AA has 16 geometry sample points and 4 texture sample points compared to ATI's 12 geometry points and 2 texture points, the distribution of ATI's sample points provide more efficient coverage. Incidentally, if ATI had named their modes like NVIDIA's AA modes, they would have said 20xAA rather than 16xAA.
NVIDIA's 4 texture sample points (essentially super-sampling/SSAA sample points) could provide better interior, texture, and transparent surface antialiasing. Unfortunately, their arrangement limits their usefulness in this regard. Thus we have to declare ATI the clear winner in the AA department. Of course, Super AA mode does take quite a performance hit as we will find out later. But take a look at what it can do to Half-Life 2 at 800x600 (no AA, 4xAA, 6xAA, 10xAA, 14xAA from top to bottom):
While differences beyond 4xAA are harder to spot, take a look at the antennae on the bottom-left of the images. You can see how the barely-visible parts are rendered better, particularly with the 10xAA and 14xAA modes. If you have the GPU performance to handle such features, they're a nice addition.
The down side of Super AA (aside from the performance hit) is that it will only run in full screen applications. Windowed applications are still stuck with 2x 4x 6x and no AA. Even if a Super AA mode is selected, only half the subpixel samples are used. We are not sure if this is a hardware or software limitation, but those of us who play MMORPGs in the background will need to be aware of this issue.
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davecason - Tuesday, September 27, 2005 - link
http://www.anandtech.com/video/showdoc.aspx?i=2541...">http://www.anandtech.com/video/showdoc.aspx?i=2541...The word "us" should be "use" in this paragraph:
The CrossFire master card is basically an X850 XT with the addition of a Xilinx FPGA (for the compositing engine) and a TMDS receiver for taking input from the slave card. Instead of 2 DVI-D ports, the CrossFire master card makes us of a high speed DMS port. This connects to one port of the CrossFire dongle and takes the slave card input as well as providing the output to the monitor.
JarredWalton - Tuesday, September 27, 2005 - link
Fixed. I think that was a minor edit by me where I fixed one error and created another. Hahaha....Wesley Fink - Monday, September 26, 2005 - link
We will be posting an in-depth review of the ATI Crossfire AMD motherboard tomorrow. One thing no site has really talked about is what a great overclocker the ATI Crossfire AMD has become. The Reference Board has the best Enthusiast level options and controls I have EVER seen on a Reference Board, the overclocking performance is outstanding, and DFI promises they will deliver the same or better in the next few weeks in their own Crossfire AMD board.Another unmentioned biggie for me is the fact that the Crossfire X850 Master Card works just fine as a standalone X850 graphics card. If you have to buy a Master Card for Crossfire I think it's important to know you can use it ALONE as an X850 card when the next hot generation graphics comes along - it's not just an investment you have to throw away.
Derek talks a bit about how the next generation graphics fixes some of his concerns about Crossfire as a TODAY purchase. His comments should make more sense in that light, and they will certainly be clearer in the next couple of weeks when X1800 launches. Just keep in mind that the same Crossfire AMD motherboard will be used with X1800 and that the motherboard also works great with an nVidia 7800GTX and any other single nVidia or ATI graphics card right now.
michal1980 - Tuesday, September 27, 2005 - link
i have to say nice numbers by ati, buti mean who in the right mind is buying a 500 dollar x850 card, a 150-200 dollar mobo,
just to get crossfire, when in 1 week or so the x520 is supposd to come out. which by the way does not appear to have any menition of crossfire support. and while true you do not have to buy the same 2 cards for crossfire to work. the 2nd master card you buy costs you 100 bucks more. phhff. sorry. the whole sli/crossfire thing really doesn't make much sense unless you are always buying at the release of the tech. i.e. when the gtx gets released u buy 2.
but why would you buy into a crossfire setup now? when the next ati cards are coming out. if there similar to the nivida one. getting 2 x800s, is like roughly spending the money on 2 6600gts, when you could for the money buy the never, and overall better 1 card solution in a 7800gtx for the same money.
or a new x520, for the same money, i'd pass on getting old tech up to speed when new stuff is/will be here soon
michal1980 - Tuesday, September 27, 2005 - link
also if u do compare the 6800ultra vs the x850, the only game the ati car wins in is in hl2. go figure, a game they basicaly wrote for there hardware with the help of gabe 'i will delay this game till ati is ready'DerekWilson - Tuesday, September 27, 2005 - link
heh ... ATI was very unhappy with Valve's launch slip. They sank a lot of money into the HL2 bundle and launch efforts for a time frame that was a year before the game actually came along.waldo - Monday, September 26, 2005 - link
So, like most people on this forum, I read both here and at Tom's Hardware...and it is amazing to me the discrepancies in the writings of the articles. I was hoping you could clarify.1. Are they just bought out by ATI, or are you guys just bought out by NVIDIA?
1a. The conclusions drawn seemed to be in the face of each other. You are dead set against, and they are seeming for ATI's crossfire. This isn't fashion, or poetry, or a film, where you just go by what you like. There are frame rates, quality of picture, etc....why are they so different?
2. It appears that the benchmarks on Tom's are slightly different in comparison to yours, in that it shows the X850 crossfire doing slightly better than the 7800 SLI configuration in several instances.
3. Tom's foxused more on the notion that you don't need two of the exact same card. Based on your article, it is your opinion that you go 7800 SLI, or single wiht hopes of 7800 SLI later, rather than x850 now, and then the addition of R520 later? It would be helpful to have some benchies of mixed card situations.
I realize that it seems attacking, and really I posted here because I like Anandtech better than Tom's but I respect both as the best resources on the net for technology reviews, but it just seems odd that the two top sites out there come down on completely different sides of the fence.
Thanks
Frallan - Tuesday, September 27, 2005 - link
THG!Well as it seems THG has in the last two year gone from beeing a "not-so-good" hardwaresite (please buy it back Thomas) to currently beeing a "outright-bought" hardwaresite. Just look at the major articles they have published the last year and U will see.
All IMHO oc.
photoguy99 - Tuesday, September 27, 2005 - link
Tom's Hardware articles seem to be trending toward less interesting and less quality over time.I still read it, but most of the time find I prefer the AnandTech version of similar subjects.
One thing that is terrible about Toms - why no direct link from articles to a discussion topic?
Not only does it make it easier to discuss, but I consider it a huge benefit the the AnandTech authors read and participate in the discussion of the articles.
DerekWilson - Tuesday, September 27, 2005 - link
Is this not a discussion? :-)