[W1zzard]

Introduction

September 2009 is a big month for both AMD and Intel in nearly equal measures. While Intel introduced its brand new socket LGA-1156 family of processors and the Intel P55 chipset to drive its platform, AMD launched the industry's first DirectX 11 compliant lineup of graphics processors, particularly the Radeon HD 5870 (our review here), which is powered by the fastest graphics processor currently available. To ensure that the graphics card is working to its full-potential, one of the important factors is the system interface, and the system's ability to provide as much bandwidth as it can to the GPU. One of the characteristic features of Intel's socket LGA-1156 processors is the on-die PCI-Express 2.0 switch that can provide a PCI-Express 2.0 x16 link for graphics.



Thanks to the modular, scalable design of PCI-Express, consisting of independent data-paths called 'lanes', motherboard designers can control a limited PCI-Express lane budget, and offer multiple PCI-Express x16 slots. In mid-range motherboards, and particularly in most motherboards based on Intel's newest P55 chipset, 16 PCI-Express lanes are used to drive two PCI-Express slots with bandwidths of 8 lanes each. These two slots can then accommodate two graphics cards for multi-GPU performance upscaling using ATI CrossfireX or NVIDIA SLI technologies. It should also be noted that PCI-Express 2.0 doubles the bandwidth available per lane. So if you read about PCI-E x8 2.0 in this review, these results are representative of a PCI-E x16 link in 1.1 mode - like on many old motherboard. Another important point to make is that PCI-Express is forward and backwards compatible. You can run any PCI-E 1.x card in a 2.0 slot or any 2.0 card in any 1.x slot, with reduced bandwidth of course.



In this review, we test the impact of running the ATI Radeon HD 5870 graphics accelerator on PCI-Express slots that are electrically PCI-Express 2.0 x8, x4, and x1. This is done by covering the data-paths using thin, insulating adhesive tape, which turns off those data-paths (lanes), while still keeping the device functional. Tests at PCI-Express 2.0 x8 will show you how the Radeon HD 5870 with its seemingly heavy system bandwidth requirement fares on systems with PCI-Express 2.0 x16 electrical x8 slots. Tests at PCI-Express 2.0 x4 will give you a rough idea of how it fares on systems with PCI-Express x16 electrical x4 (there are plenty of such motherboards), and also systems with PCI-Express 1.1 x16 electrical 1.1 x8. Finally, we dared to run this monstrosity on just one PCI-Express 2.0 lane. Not only was it functional, but also stable, returning results on all the tests we threw at it. While not serving any practical purpose, tests on PCI-Express x1 are merely of academic relevance.

Test System

Test System
CPU:	Intel Core i7 920 @ 3.8 GHz (Bloomfield, 8192 KB Cache)
Motherboard:	Gigabyte X58 Extreme Intel X58 & ICH10R
Memory:	3x 2048 MB Mushkin Redline XP3-12800 DDR3 @ 1520 MHz 8-7-7-16
Harddisk:	WD Raptor 740ADFD 74 GB
Power Supply:	BFG ES-800 800W
Software:	Windows Vista 32-bit SP2
Drivers:	NVIDIA: 186.18 ATI: Catalyst 9.6, HD 5870: 8.66 RC6
Display:	LG Flatron W3000H 30" 2560x1600

• All video card results were obtained on this exact system with the exact same configuration.
• All games were set to their highest quality setting

Each benchmark was tested at the following settings and resolution:

• 1024 x 768, No Anti-aliasing. This is a standard resolution without demanding display settings.
• 1280 x 1024, 2x Anti-aliasing. Common resolution for most smaller flatscreens today (17" - 19"). A bit of eye candy turned on in the drivers.
• 1680 x 1050, 4x Anti-aliasing. Most common widescreen resolution on larger displays (19" - 22"). Very good looking driver graphics settings.
• 1920 x 1200, 4x Anti-aliasing. Typical widescreen resolution for large displays (22" - 26"). Very good looking driver graphics settings.
• 2560 x 1600, 4x Anti-aliasing. Highest possible resolution for commonly available displays (30"). Very good looking driver graphics settings.

BattleForge

BattleForge, a card based RTS, is developed by the German EA Phenomic Studio. A few months after launch the game was transformed into a Play 4 Free branded game. That move and the fact that it was included as game bundle with a large number of ATI cards made it one of the more well known RTS games of 2009. You as a player assemble your deck before game to select the units that will be available. Your choice can be from forces of Fire, Frost, Nature and Shadow to complement each other.
The BattleForge engine has full support for DX 9, DX 10 and DX 10.1, we used the internal benchmark tool to acquire our results.

Call of Duty 4

Call of Duty 4 is a first-person shooter that is built on the award winning Call of Duty Series. It is the first version to play in modern times. In a near-future conflict between the United States, Europe and Russia you get to play as a United States Marine and a British SAS operative. The engine is Infinity Ward's own creation and has true dynamic lighting, depth of field, dynamic shadows and HDR. Even though the game plot is scripted you will find yourself in intense battles, often working together with computer controlled team mates.

Call of Juarez 2

Call of Juarez 2: Bound in Blood is a prequel to the first Call of Juarez game which was one of the first DX10 titles available on the market. This time the plot evolves around two brothers, before each mission you may pick one to play. Your choices affect the game play since both characters have different ways of handling situations and doing combat.
Call of Juarez 2 uses Techland's Chrome Engine 4 which adds Edge Anti Aliasing as one of the first engines on the market. Edge Anti Aliasing looks similar to normal AA but comes with a considerably reduced performance drop. However, due to the deferred shading design of Edge AA, normal AA can't be used on top of it.

Company Of Heroes

The real-time strategy game Company of Heroes is set during World War II where you take two American companies through several fights all over France to liberate the country from German occupation. Company of Heroes is the first game to use Relic's next-generation engine "Essence Engine" which includes support for HDR lighting, Shader Model 3.0, normal mapping, dynamic lighting and shadows. You are able to zoom in from the tactical view of the battle field to see the individual units fighting. Often you catch yourself admiring the detailed animations of the soldiers while the fight around you is raging.

Crysis

After the tremendous success of Far Cry, the German game studio Crytek released their latest shooter Crysis in 2007. The game was by far the most hyped and anticipated game in 2007, the forums were full of "Can my system run Crysis?" threads because of the high hardware requirements of this game. Just like in Far Cry the plot evolves on a small island with a thick and richly detailed jungle world. A lot of attention has been given to small details like correct physics. For example when you fire on a tree trunk, it will shatter and the tree will fall over leaving a stump behind. Enemies in a car can be stopped by shooting the tire of the car. The game graphics are by far the best ever seen in a PC game so far, yet the game still runs well on most computers.

Warhammer 40,000: Dawn of War 2

Warhammer 40,000: Dawn of War II by Relic Entertainment is an RTS game based on the Warhammer 40,000 universe. Unlike other Dawn of War titles there is no base-building element in the game, you simply command units on the battlefield. Due to the non-linear mission design, the choices which mission and objective you pick to pursue have considerable impact on game play and mission difficulty. A "hero" unit concept adds RPG elements to the game, allowing you to advance the unit in terms of levels and abilities. Dawn of War 2 uses the Essence Engine 2.0, version 1.0 was used in the Company of Heroes Series.

Enemy Territory: Quake Wars

The first-person shooter Enemy Territory: Quake Wars is set in the science-fiction universe of Quake and requires several classes to work together to achieve certain goals on a map. In the campaign mode you gain experience which you can use to buy upgrades for your class. The player gets to pick from five classes of either the Global Defense Force or the Strogg faction. As underlying game engine, the successful id Software Doom 3 engine has been licensed, but several features like MegaTextures have been added, giving the outdoor world a much more detailed appearance.

Far Cry

Far Cry was released in early 2004 by the new development studio Crytek. It quickly became a massive success because it was one of the first titles to take you in a beautiful 3D outdoor world. Far Cry was one of the most demanding games at its time. Even with today's video cards you can still see big differences in frame rates, especially at the higher resolutions.

Far Cry 2

Four years after the success of Far Cry, Ubisoft has published the sequel called Far Cry 2. While the first part was set on an island, Far Cry 2 takes you deep into Africa with game play that resembles Grand Theft Auto much more than the original Far Cry, which was a classical 3D shooter. Ubisoft engineered a completely new 3D engine called "Dunia" which offers a large amount of popular features like DirectX 9 and DirectX 10 support, destructible environments, physics and non-scripted AI while not being as much of a resource hog as Crytek's CryEngine.

FEAR

The first person shooter F.E.A.R, developed by Monolith Game Studios, was released in Fall 2005 and has a great 3D engine that uses a large number of shading and shadow effects to accurately model the game world. In addition to that it features a realistic physics engine that lets you interact with many objects in the game world. The game was voted game of the year by several publications.

Tom Clancy's HAWX

Tom Clancy's H.A.W.X. is one of the very few recent flight simulator games on the market. Being a console conversion it emphasizes "flight" more than "simulator". It is set in a near future in which private military companies have begun fighting conflicts for nations with their own military gear. You are playing an elite pilot who was recruited by such a private company. During the game you get to fly over 50 different aircrafts, ranging from the MIG 21 to the mighty F22 Raptor. One notable feature of its engine is the use of GeoEye satellite imagery for terrain generation which offers one of the most realistic incarnations of battlefield terrain available today.

Prey

Prey is based on a highly modified 3D engine made by id Software. This first person shooter brought a completely new way of gaming to the genre. In many levels you find yourself walking upside down or on the walls. This adds a completely new aspect to the gaming experience in this genre.

Quake 4

The Quake titles are among the most successful first person games. Developed by id Software, the famous game studio that brought you DOOM, you find yourself in a sci-fi world that is full of aliens and shocking effects. The main focus of the game is the single player story line. Quake 4 puts you on the home planet of the Strogg. In a number of missions you and your fellow marines will encounter all sorts of enemies, including some really huge aliens.

The Chronicles of Riddick: Assault on Dark Athena

The Chronicles of Riddick: Assault on Dark Athena is a first person shooter game set in a far future. You are Riddick, a notorious space criminal played by Vin Diesel in the movies. Dark Athena continues where Escape from Butcher Bay ended. A major aspect of the game is its tactical use of shadows and stealth so that enemies can't detect you. Vin Diesel's voice acting also adds greatly to the game experience.
The 0.0 FPS scores for NVIDIA cards at 2560x1600 are caused by driver crashes which seem to be related to card with 512 MB memory and below. Since it works fine on ATI this is not a game problem but an NVIDIA driver issue.

S.T.A.L.K.E.R.

Before its release in 2007, S.T.A.L.K.E.R.: Shadow of Chernobyl was one of the most hyped games of the last years. This RPG/FPS hybrid game is set a few years in the future, after a nuclear disaster occurs at the Chernobyl Nuclear Power Plant. The release of radiation causes strange things like mutations in the nearby area. You take the role of a Stalker who seeks fame and riches in the contaminated area around Chernobyl. The game engine features all the latest buzzwords like HDR, bullet physics, skeletal animation, soft shadows and weather effects. Stalker's vast outside world is richly modeled, you can interact with a large number of objects in the game thanks to the physics engine.

S.T.A.L.K.E.R. - Clear Sky

STALKER Clear Sky is GSC Gameworld's prequel to the 2007 hit "STALKER". Just like in the first part the game is set around the Russian area of Chernobyl and Pripyat, most well known for the nuclear accident that occurred there. You play the role of a mercenary who spends his days in The Zone trying to make a living. The Zone is an area which is affected by so-called anomalies which cause mutants to appear and laws of physics to change. While you investigate these anomalies the plot leads up to the events that happened right before the first game starts. A new in-game faction system encourages you to befriend various groups in The Zone in exchange for information or items. While the graphics of Clear Sky are based on the first Stalker game engine, there are numerous improvements, including support for DirectX10 and depth-of-field/volumetric effects.

Team Fortress 2

Team Fortress 2 by the famous people from Valve software builds on an improved Half-Life 2 engine to deliver an action packed, team oriented, comic graphics first person shooter game. Even though the game features nice graphics, it tends to be very CPU limited, especially on lower resolutions. Players get to team up being either RED or BLU with a selection of nine classes. Each class offers a different play style, just like in the original Team Fortress games.

Unreal Tournament 3

The fourth game in Epic's highly successful Unreal Tournament Series is simply called Unreal Tournament 3. It is based on the all-new Unreal 3 engine which is a major step forward from the previous engine. The game principle is centered about an arena style gameplay where several contestants try to reach a certain kill count or capture a flag for example. As you would expect from a new 2007 title, the graphics are top notch, with large and detailed textures. One major drawback of the way the engine is designed is that there is no support for Anti-Aliasing.

World In Conflict

The realtime strategy game World In Conflict by Massive Entertainment is set in 1989 taking the player through a fictional conflict during the collapse of the Soviet Union. Unlike other RTS games, World in Conflict is not centered around building a base, you command units on the battlefield with a number of reinforcement points available to replace lost troops.
Massive's Masstech Game Engine makes heavy use of level-of-detail techniques which allow you to zoom in closely on the action displaying fights in high-fidelity with a large number of effects.

3DMark03

Futuremark Corporation is the number one player in the world of synthetic benchmarking. The 3DMark series is the most popular test suite for video card testing and is used by gamers, overclockers and manufacturers alike to determine how fast their hardware is. Even though it is a few years old, 3DMark03 can easily stress today's video cards.

3DMark05

Another benchmark from Futuremark is 3DMark05 which comes with four completely new game tests that make massive use of shaders and lighting effects. 3DMark05 is a great test for modern video card architectures - in some tests you are often close to the 30 fps mark, below which your games will feel sluggish.

3DMark06

Even though it's based on Futuremark's 3DMark05, the new 3DMark06 adds new tests for Shader Model 3.0 and HDR rendering. It is also the first 3DMark to incorporate a CPU score into the final 3DMark score. All tests have received an overhaul, for example in the Canyon Flight test you can now see beautiful sun glare effects with the help of High Dynamic Range rendering.

Performance Summary

To create this graph we took all performance results of the four resolutions we tested, threw them together and calculated the relative performance of each card, compared to our review sample. In a fifth graph we also combined all tests in all resolutions to calculate the total relative performance of the review sample.

Conclusion

What an interesting mix of results! Let's begin our inference of the results by saying that for the Radeon HD 5870, the PCI-Express 2.0 x16 is the broadway it can fit all its four wheels on, and try some road stunts, while it's at it. PCI-Express 2.0 x8 performance, which is perhaps the most crucial set of figures in this review, holds relevance to most people looking to pair two of these cards on mid-range motherboards or one of these cards on an x16 1.x motherboard. It holds even more relevance to users and potential-users of most socket LGA-1156 motherboards, as this is where 16 lanes from the processor's on-die PCI-E switch are split into two 8 lane links. Surprising as it seems, the Radeon HD 5870 is comfortable, with a mere 2% performance drop overall. PCI-Express 2.0 x4 is where the Radeon HD 5870's discomfort is slightly notable, with a 5% drop, and even more surprisingly, on PCI-Express 2.0 x1, big as it seems, the performance drop is "only" 25% overall. Considering that you rob the card most of its data transfer potential, leaving only a 1/16th of the optimum bandwidth, it is still impressive that it can deliver 75% of its performance.

Different applications respond differently to the drop in interface bandwidth, and hence you could do with a closer look at the results for each application. Games with lighter texture, shader, and instruction data don't particularly need all 16 lanes, and evidently, in games such as Quake 4, you're able see the accelerator comfortable with even PCI-Express 2.0 x4. Video memory-intensive games will show bigger performance margins. Besides applications, the other important factor is the resolution at which they are being run. At higher resolutions, it pays to have higher interface bandwidth, as it's usually high-resolution textures the GPU is dealing with. Although small, the gaps widen with increase in resolution. However, it is important to realize that even at 1024x768 some applications will see serious differences in performance caused by PCI-Express bandwidth.

Our bottom-line on this subject is that there is every reason to be optimistic when opting for two of these accelerators on motherboards with two PCI-Express 2.0 x16 (electrical x8) slots, because the performance penalty between that and PCI-Express 2.0 x16 (electrical x16) is just too small. Unless you're the quintessential enthusiast and every frame per second increase matters to you, there is no reason to worry about a performance drop on mid-range motherboards, although this is only one of the factors, a main one at that, to contribute to the performance drop. Some motherboard manufacturers are offering a third PCI-Express x16 slot that is electrically x4. The results show that the performance drop isn't as bad as one would imagine, so we will green-signal installing a third accelerator for some 3-way ATI CrossfireX action, or 2-way CrossfireX on entry-level Intel P55 motherboards with the second x16 slot electrically x4 (running in 1.0 mode). If you're crazy enough to mod a PCI-Express x1 slot (by carefully cutting its end to let it seat a PCI-Express graphics card), then the scores should really dishearten you. Buy one of these accelerators now, add one later, and you will have secured yourself future-proofing.