CrossFire and Test Setup


CrossFire with the R7870 HAWK


It is not secret that AMD is a bit behind NVIDIA when it comes to multi-GPU functionality.  That being said, AMD is still leaps and bounds from where they once were.  We saw a pretty significant jump in scaling from the HD 5000 series to the HD 6900 cards.  One issue that does crop up in discussion is the amount of “micro-stutter” that the AMD cards have as compared to the NVIDIA SLI solutions.  Something that is not widely known among users is that NVIDIA has dedicated units in each GPU which help to even out frame rates and cuts back on the stutter.  So while the NV and AMD multi-GPU solutions may benchmark fairly evenly with each other, most users will agree that the NV solution does feel smoother.

The cover of the GPU Reactor dominates the back of this board.  Note as well the nice cover for the entire back, which protects the PCB and provides rigidity.

That being said, I decided to give CrossFire another shot with the latest HD 7870 cards.  I used the Catalyst 12.6 beta release drivers which not only fixed a bunch of issues, it also improved performance and compatibility with many games in CrossFire.  The cards were instantly recognized by Windows 7 and CrossFire was enabled once the drivers were installed.  The HD 7870 cards only have one CrossFire over-the-top connection, so tri and quad card solutions are not available for this level of product from AMD.


Test Setup


The base system is an overclocked Phenom II X6 1100T.  It is set at a constant 3.7 GHz instead of the standard 3.3 GHz with six cores and the turbo mode of 3.7 GHz with three cores or less.  I have been using this CPU rather than the latest FX-8150 because it honestly has better overall performance and is a far less choppy CPU in these applications.  This will likely change when Vishera hits the market, but for the time being I am still very interested in gaming performance with high end cards on the AMD platform, and this is the best CPU that AMD has to date for gaming.

Removing the plastic cover reveals the secondary PCB that powers the GPU Reactor.  Tantalum capacitors as far as the eye can see…

I tested the MSI R7870 Hawk against the XFX R7850 DD Black Edition and the MSI R7950 TFIII/OC.  The R7850 comes in at approximately $274 and has 1024 stream units clocked at 975 MHz combined with 1250 MHz (5000 MHz effective) memory.  The $329 MSI R7950 has 1792 stream units clocked at 880 MHz and a 384 bit memory bus at 1250 MHz (5000 effective).  I tested the R7870 in CrossFire, but I utilized a 1250 MHz memory speed rather than the stock 1200 MHz.  We will see that MSI was a bit conservative when it comes to memory speed, and at the core 1100 MHz GPU clock, it is somewhat memory starved.

I like to test these setups in actual cases, and I used the new Enermax Fulmo GT case as the basis for this review.  Previously I had used the Silverstone Raven RV02, but that case was getting a bit long in the tooth when it comes to design.  The Fulmo is much more spacious, has far superior cable routing, and is packed full of fans to keep even the hottest video card cool.  I also started using the Corsair AX1200 power supply, which is probably one of the absolute best units that can be found on the market.  A bit pricey, but very efficient and can push any video card on the market (in single and multi-GPU configurations).

The top card is the upcoming GTX 670 Power Edition, followed by the R7870 HAWK, with the last gen HD 6950 Twin Frozr II.  Oh, how the HAWK has grown…

Phenom II X6 1100T @ 3.7 GHz

GSkill 2 x 4GB DDR-3 1600 @ timings

Asus SABERTOOTH 990FX Motherboard

Corsair AX1200 Power Supply

Western Digital Caviar Black 1TB HD

Lite-On BDR-Drive

Enermax Fulmo GT Full-size ATX Case

Windows 7 Ultimate 64 Bit

Catalyst 12.6 Beta Drivers

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