ATI HD 2900XT CrossFire: Intel 975X versus Intel P35

Test Setup

Our test configurations today consist of the ASUS P5K-Deluxe sporting the new P35 chipset and the Intel D975XBX2KR based on the venerable 975X chipset. Our retail P5K-Deluxe board was purchased recently even though an embargo is supposedly in place until June 4th for distribution of P35 product. Likewise, P35 boards from other suppliers such as MSI and Gigabyte can also be purchased at this time making this one of the stranger product releases in recent memory.

The P5K-Deluxe features ASUS's C.G.I. technology from their P965 motherboards. ASUS C.G.I. stands for ASUS Cross Graphics Impeller (marketing still reigns) and is a feature that when enabled will automatically optimize system performance if a CrossFire configuration is detected. These optimizations occur within the Direct Media Interface between the P35 MCH and ICH9R that is utilized to enable CrossFire operation on this motherboard.

The 975X chipset utilizes Peer-to-Peer write capability within the MCH to enable 2x8 PCI Express lane capabilities for CrossFire. This feature is not available in the P965 or P35 without a special PCIe controller chip and BIOS support. ATI/AMD enables CrossFire support utilizing the Direct Media Interface (DMI) to link the x16 GPU slot (16 PCI Express Lanes) residing on the MCH and the x4 GPU slot (4 PCI Express Lanes) residing on the ICH. Contrary to rumors and initial reports in certain forums, the P5K-Deluxe does not perform CrossFire operations with a 2x8 PCI Express lane configuration.

Standard Test Bed CrossFire Test Configuration
Processor	Intel Core 2 Duo QX6700 (2.66GHz, 8MB Unified Cache)
RAM	OCZ Reaper PC2-9200 (4x1GB) 2.32V, 3-3-3-9 975X, 4-4-3-6 P35
Hard Drive	Western Digital 150GB 10,000RPM SATA 16MB Buffer
System Platform Drivers	Intel - 8.3.0.1013
Video Cards	2 x MSI HD2900XT
Video Drivers	ATI 8.37.4.3 (HD2900XT Release Drivers)
CPU Cooling	Tuniq 120
Power Supply	OCZ ProXStream 1000W
Optical Drives	Plextor PX-760A, Plextor PX-B900A
Case	Cooler Master CM Stacker 830
Motherboards	Intel D975XBX2KR (Intel 975X) - BIOS 2692 ASUS P5K Deluxe (Intel P35) - BIOS 0304
Operating System	Windows Vista Ultimate 64-bit
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Test conditions were maintained the same, as much as possible, over the platforms tested. Our game tests were run at settings of 1280x1024 4xAA, 1600x1200 4xAA, and 1920x1200 4xAA with 8xAF implemented in games that support this feature. These settings were used on both our single card and CrossFire setups. We feel like these settings and resolutions will provide accurate benchmark results for the typical user utilizing a CrossFire setup with a high end CPU.

All results are reported in our charts and color-coded for easier identification of results. We utilize new drive images on each board in order to minimize any potential driver conflicts. Our 3DMark results are generated utilizing the standard benchmark resolution for each program. We run each benchmark five times, throw out the two low and high scores, and report the remaining score. All results are run at stock speeds for this article although we will provide overclocked results in the next article. For those wondering, our cards generally had no issues running at 853/1000 provided we had notified the electric company of a pending power surge.

This preview is not a graphics card review and as such we are not including results with products from the Big Green Machine yet. Those comparisons will come in our P35 chipset article. We are simply providing results on how each chipset handles CrossFire operations at this time. We will provide P965 and RD600 results in our follow-up to this article so you can have a clear picture of which Intel chipset performs the best with a CrossFire configuration. We might even throw an RD580 into the mix to see how well the R600 performs on it.

We also booked several sessions with a psychologist so we can understand why there was a lapse in our thought process for choosing Windows Vista Ultimate 64-bit as our operating system. The R600 already has enough early driver issues to make one think twice about using it, but to throw a new operating system and chipset into the mix and then to push matters further by going 64-bit was clearly not the actions of a sane person. It sounded good at the time, it really did, but after several days of constant frustration, hair pulling, dog kicking (relax PETA, just a joke), finger nail chewing, and general panic attacks about missing the article deadline... well, we would have not have done it any differently as it turns out.

Why? Whether we like it or not, Vista is the future of Windows for the time being and is required for DirectX 10. Honestly, it was time to see how far the various vendors had come since release in providing decent driver or game support. 64-bit OSes are also the future - after all, AMD released x86-64 on the world over three years ago. We collected enough information to generate a weekend short story on the subject but as we feared, progress has been slow.

NVIDIA released their first decent set of Vista drivers this last week and we are busy redoing all of our 8800GTS/GTX numbers for the P35 launch article. In the meantime, we chewed through four different driver releases from AMD and decided to stick with the publicly released 4.37.4.3 drivers for this article. We generated some really impressive 3DMark numbers with the alpha 4.37.4.2 drivers but let's just say when it came time to using actual applications those drivers were not always stable or feature capable. We did receive a new set of beta 8.38 drivers a couple of days ago and those are in testing but we do not have enough experience with them yet to publish meaningful numbers.

You might notice in our game testing that several of the more popular games are not benchmarked. We had screen corruption issues in Oblivion, S.T.A.L.K.E.R., Half-Life 2: Episode One, and even Sims 2 when utilizing CrossFire. These same issues are not evident under Windows XP so we contribute most of the issues to driver maturity, though several games we tried are also having some minor issues with XP as well. Also, our Battlefield 2142, Flight Simulator X, and Half-Life 2: Lost Coast benchmarks would not run consistently under Vista so we are back to the drawing board on those and a couple of other games.

As for providing current DX10 benchmarks from the upcoming Lost Planet and Call of Juarez games we decided it was best to wait on the next driver release before providing results as any scores generated now are basically useless. When running CrossFire with the R600 each demo has problems with rendering, tearing, jitters, and several other issues that are likely to be fixed shortly. Needless to say, our first experiences with DX10 and the R600 were not pleasant.