 | |||
|
|
|
|
|
 |
ATI CrossFire Performance Preview September 26, 2005 Brandon Sandman Bell |
|
 |
|
| |
Summary: After months of delays, ATI's CrossFire platform is finally shipping, and with a new lower price! See how dual X850 XT boards stack up against NVIDIA's latest and greatest, including the GeForce 7800 GT/GTX and the GeForce 6800 Ultra in single and SLI configurations in this article!
 Introduction | Page:: ( 1 / 11 ) |
ATI’s CrossFire technology was first announced with much fanfare at Computex back in June. At the time ATI expected the first retail products to hit shelves one month later in July. Unfortunately for ATI however, July and then August passed without any shipping products, all while archrival NVIDIA successfully launched not one, but two next-generation graphics products capable of delivering significantly more performance than anything else on the market.
ATI’s equivalent next-generation product, the RADEON X1800 is still missing in action, although it’s now known that ATI will be officially introducing it early next month. ATI recently updated the frontpage of their website with a countdown to the X1800 launch, and have issued a press release stating that their high-end, mainstream, and value cards are all in full production and are being built on TSMC’s 90-nanometer manufacturing process. The arrival of these cards can’t come soon enough for ATI, as NVIDIA is not only picking up mind share among enthusiasts, but also OEM design wins among system manufacturers. Losing these sales has put a large strain on ATI’s balance sheet, with the company recently revising their Q4 revenues downward by roughly $100 million dollars.
[image]
| <% print_image("01"); %> | <% print_image("02"); %> |
With all the hubbub surrounding the R520 delay and ATI’s recent financial woes, CrossFire was slowly forgotten.
The root cause of CrossFire’s delay is unknown. Back at Computex ATI was pretty adamant that the hardware was ready, they were just waiting on the drivers. Multiple board partners had their CrossFire products on live displays, and all of them were pretty confident that ATI would deliver products on time: after all, the motherboards were just an adaptation of ATI’s XPRESS 200 chipset, just as the CrossFire graphics cards were largely based on ATI’s previous reference graphics board designs. We then saw more evidence of this for ourselves at the show when we attempted to run a few tests on a CrossFire system with 6xAA, only to see it crash a few seconds later.
[image]
| <% print_image("03"); %> | <% print_image("04"); %> |
Whatever the reason for the delay, CrossFire is here now, just in time for existing RADEON users who may be tempted to upgrade this winter, or those of you who may want to build a new system from scratch. With the GeForce 7800 GTX and 7800 GT firmly entrenched at the high-end of the market, ATI has adjusted their pricing on CrossFire since their June launch, with X850 XT CrossFire officially retailing for $349 while the X800 XL CrossFire and X800 CrossFire boards carry an MSRP of $299 and $199 respectively.
Basically, ATI’s positioning the X850 XT CrossFire configuration to challenge NVIDIA’s older GeForce 6800 Ultra SLI, as X800 XL CrossFire competes with two GeForce 6800 GTs and finally, the X800 CrossFire does battle with GeForce 6800 vanilla.
But how well does CrossFire run? That’s what we’re here today to find out.
| The technology | Page:: ( 2 / 11 ) |
One of the oldest methods used to accomplish this is to split the screen in half, with one graphics card handling the top section while the second card is responsible for the lower segment. The frame buffer data is then combined and sent to the monitor. It’s important to note that while we say split in half, the screen isn’t split perfectly in the middle as in some scenes the bottom of the screen may be more complex than the top, or vice versa. The screen can also be split horizontally or vertically. The driver determines the most efficient way to split the workload on the fly as conditions change.
ATI has dubbed this mode “scissor mode”. This is CrossFire’s default mode for OpenGL and also works in Direct3D applications as well.
[image]
| <% print_image("05"); %> | <% print_image("06"); %> |
The second mode that’s probably familiar to many of you is alternate frame rendering (AFR). ATI made this mode famous with their Rage Fury MAXX graphics cards a few years back. With AFR, each card handles alternating frames. Graphics core one handles everything in frame 1, while graphics core two then handles all of frame number 2. Both chips will continue to repeat this process, with one card handling the even frames, while the second card is responsible for the odd-numbered frames. Each chip renders every other frame instead of alternating portions of the same frame, as the other methods do. The completed frames from both cards are then sent to the compositing engine on the CrossFire board, which then sends them to the display.
Alternate frame rendering is available for both OpenGL and Direct3D applications. It’s the method used for all DOOM 3/Quake 3 engine games, with scissor mode being used for older OpenGL applications.
The final rendering mode ATI CrossFire supports is supertiling. In supertiling, the scene is split into 32x32 squares known as “tiles”. Each card then handles alternating tiles, which are then output to the display. By splitting the workload into small tiles, it can be distributed very close to an even split
Supertiling is the preferred rendering mode for Direct3D applications, but isn’t available for OpenGL.
The key ingredient that makes all this happen is the compositing engine chip, which is located on the CrossFire graphics card. The compositing chip takes the data from its local RADEON VPU and combines it with the data from the slave graphics card, which it receives over a DVI connection. The chip is responsible for handling all communication between the two cards, as well as handling blending and arithmetic operations. From there the CrossFire card outputs the image via DVI adapter to the monitor, where it’s displayed on your screen.
Better Anti-aliasing
Besides performance, another key addition CrossFire supports is better AA. Both graphics cards use slightly different sampling patterns which are then blended together by the compositing engine to produce the final image, ultimately providing sharper visuals. CrossFire also provides new AA modes. In addition to the standard 2, 4, and 6 sample AA modes ATI has provided previously, CrossFire also supports 8x, 10, 12x, and 14x modes.
For CrossFire’s 8xAA mode, both cards are running in 4xAA mode, for an effective equivalent of 8xAA likewise at 12xAA, both cards are running in 6x mode. The 10x and 14x modes mix multisampling with supersampling for even better image quality. At the 10x setting for example, the cards mix 8x multisampling with 2x supersampling, while 14x combines 12x multisampling with 2x supersampling.
| First impressions | Page:: ( 3 / 11 ) |
ATI has also partnered with Intel to deliver CrossFire to Intel’s 955X platform, at IDF ATI and Intel demonstrated a CrossFire system up and running with Intel’s high-end chipset running flawlessly. ATI could potentially work to bring CrossFire support to other platforms, such as VIA’s chipset solutions or perhaps even nForce4, although it’s doubtful NVIDIA would be interested in allowing that to happen.
[image]
| <% print_image("07"); %> | <% print_image("08"); %> |
Installation and setup
Setting everything up is a bit different than NVIDIA’s SLI, particularly since the compositing chip removes the need for an SLI connector. Instead you’ll use the CrossFire interconnect cable to hook up the two cards, as well as your monitor. It all kind of works like 3dfx’s pass thru cable back in the Voodoo 2 days. On one end of the CrossFire interconnect cable you’ll find a DMS-59 connection, this plugs straight into the back of your CrossFire Master card. On the other end of the DMS-59 connector is a DVI connection, this is what plugs into your monitor. Finally, hooking off the CrossFire interconnect cable is a second DVI connector, this goes into the secondary (slave) RADEON graphics card.
[image]
| <% print_image("09"); %> | <% print_image("10"); %> |
Once you understand the connections, you simply plug in both graphics cards (with the CrossFire card required to be installed in the primary PCI-E graphics slot), and hook up the auxiliary power connector. The auxiliary power connector provides a little extra power to the PCI-E graphics slots, and is the same 4-pin Molex power connector you’d use for your hard drive or DVD-ROM drive.
Finally make sure that the dual slot GFX configuration setting in BIOS is set to enabled.
After you’ve finished hooking everything up, you should see an option for CrossFire in the CATALYST CONTROL CENTER. CrossFire is a CCC exclusive feature, so those of you who are still running ATI’s conventional control panel will have to install CCC if you’d like to run CrossFire, at least that’s the case with ATI’s latest driver. Simply click the checkbox to enable CrossFire, and voila, you should be done.
[image]
| <% print_image("11"); %> | <% print_image("12"); %> | <% print_image("13"); %> |
For those of you who’d like to upgrade in stages, we should also mention that ATI also includes an additional transposer card with CrossFire. This card is for single graphics card operation. The transposer card has to be plugged into the empty PCI-E slot in order to enable all 16 PCI-E lanes to the graphics card. Without the card in place while in single-GPU mode, the motherboard will default to x8 PCI-E lanes (once in CrossFire mode, both graphics cards use 8 PCI-E lanes, just like NVIDIA SLI).
| Test Systems | Page:: ( 4 / 11 ) |
System Setup
AMD Athlon 64 FX-57
ASUS A8N-SLI Deluxe
ATI RADEON XPRESS 200 CrossFire reference motherboard
1GB OCZ DDR400 SDRAM with 2-2-2-5 timings
NVIDIA GeForce 7800 GTX Reference Board
EVGA e-GeForce 7800 GT
Driver version 78.01
ATI RADEON X850 XT 256MB
ATI RADEON X850 XT CrossFire Edition
CATALYST 5.8 with CATALYST CONTROL CENTER
250GB Maxtor Hard Drive Maxline III SATA Hard Drive w/16MB Cache
Windows XP Professional SP1
DirectX 9.0c
Benchmarks
Pacific Fighters
Far Cry 1.31
Half-Life 2
F.E.A.R. Beta
Battlefield 2
| Pacific Fighters | Page:: ( 5 / 11 ) |
Pacific Fighters - OpenGL
| Far Cry Training | Page:: ( 6 / 11 ) |
Far Cry – Direct3D
| Half-Life 2 | Page:: ( 7 / 11 ) |
Half-Life 2 – Direct3D
| Battlefield 2 | Page:: ( 8 / 11 ) |
Battlefield 2 – Direct3D
| F.E.A.R. Performance | Page:: ( 9 / 11 ) |
F.E.A.R. Beta – Direct3D
| F.E.A.R. 4xAA/16xAF | Page:: ( 10 / 11 ) |
F.E.A.R. Beta – Direct3D
| Conclusion | Page:: ( 11 / 11 ) |
If you already have a RADEON X800 XL or X850 card, you may consider CrossFire to be a solid way to get more performance out of your system. Unfortunately you’ll need to replace that brand new PCI-E motherboard you just bought earlier this year or late last year, with an XPRESS 200 CrossFire board, as well as purchase the second graphics card. And it’s here where things become complicated for ATI and their CrossFire board partners.
Even going with a best-case scenario where an XPRESS 200 CrossFire motherboard would cost you about $100, you’d still need to buy the second RADEON X800 XL card for another $300, setting you back $400 total. As an alternative, for $400 you could instead invest in a GeForce 7800 GT, which would give good performance, plus the ability to play at widescreen and super hi-res resolutions such as 2048x1536.
That’s right, the rumors you’ve been hearing about CrossFire being limited to 1600x1200 max resolution at a headache-inducing 60Hz are unfortunately true. How ATI’s engineers could have overlooked this limitation when developing CrossFire – a product which doesn’t really shine until you crank up the screen resolutions – is pretty baffling. To add insult to injury, we couldn’t get DOOM 3’s timedemo mode to work properly with CrossFire.
When you factor this in with the imminent release of RADEON X1800 and its related mainstream and value offerings, R4xx-based CrossFire makes even less sense from a practical standpoint. These next-gen cards will deliver shader model 3.0 and significantly more performance for likely the same price.
That’s not to say CrossFire doesn’t have its merits, ATI’s SuperAA mode is definitely a nice feature. And let’s face it CrossFire spurred NVIDIA on to improve their SLI implementation. Do you really think NVIDIA would be providing the ability to mix and match board vendors for SLI if it weren’t for CrossFire? NVIDIA had never mentioned SLI anti-aliasing prior to CrossFire either.
In our opinion, this is the greatest benefit ATI’s first generation of CrossFire products has brought us. It’s really a shame that the first products have come to market so late, as CrossFire could have had the potential for much more. As it stands now though the ATI products we’re most interested in are RADEON X1800, RADEON X1600, and RADEON X1300. We have a pretty good feeling you probably feel the same way too.
Even with the new reduced pricing, CrossFire is still a victim of bad timing. That’s the bottom line from our perspective.