Tuesday, June 15, 2010

Gamers: Do You Need More Than An Athlon II X3?



Gamers: Do You Need More Than An Athlon II X3?

AMD's Athlon II X3 440 is such a capable little chip, and and it costs so little. Is there any real point in spending more money on your gaming machine’s CPU? We explore this question with a head-to-head challenge against Intel's venerable Core i7-920.

Every month, we publish our Best Gaming CPUs For The Money column. This is where we share our picks for the processors that we feel provide the best gaming value for your hard-earned dollar. Our recommendations are based on a lot of testing, and that testing has shown that games respond best to high clock speeds.

However, our benchmarks also show that the number of processor cores is a secondary consideration. There is a large performance jump from single- to dual-core CPUs, but most games only show a slight performance increase when a third core is added. In fact, it is rare to find a game that will take advantage of more than three processor cores and demonstrate a notable performance increase.

Since its release, the Athlon II X3 440 has had a strong impact on our recommended gaming CPU list. When you combine its high 3 GHz clock speed, trio of processor cores, and sub-$90 price tag, you end up with a real force in the gaming arena. On top of that, the third processing core allows the Athlon II X3 to be an especially great processor compared to dual-core models because that extra core can smooth out desktop performance when multitasking.

When it comes to gaming, though, the CPU can only do so much; the graphics subsystem is key. We've received some feedback on the forums suggesting that our recommendation of any processor more expensive than the Athlon II X3 440 is frivolous. The argument is that, while game performance may increase with a costlier CPU, the money is wasted because the Athlon II X3 440 is supplying all the performance that games require to achieve smooth frame rates, and that upgrading the graphics cards is the only way to remove a meaningful game performance bottleneck.

We decided to run a series of tests to really explore whether or not there's any point in investing in a CPU more powerful than the Athlon II X3 440 for gaming duty. First, we need to examine how we measure game performance and get a better understanding of how meaningful the numbers are.

We measure game performance by the speed at which frames of video are fed to our eyes. The preferred unit of measure is frames per second (FPS).

There is a common misconception that 24 or 30 FPS is enough for perfectly smooth video, or that the human eye can only perceive up to 30 FPS. This stems from the movie and television industries. Movie theaters show film at 24 FPS, and that appears perfectly smooth, doesn't it? The fact is that our eyes are tricked into experiencing smooth video from 24 FPS source material because of motion blur. Film and video cameras capture moving objects by blurring their edges and the brain interprets this as smooth movement.

If you've ever had the chance to see a demonstration of movie playback at your local home theater electronics outlet, you might have noticed that movies seem a lot smoother than they do in theaters on some of the displays. This is because many modern televisions can modify the video, smoothing it out with anti-judder technology, and play it back at 120 Hz (or 120 FPS). Most folks easily notice the visual difference when movies are played back at 120 FPS with anti-judder enabled, which goes to show the human eye can perceive a lot more than 24 FPS. In fact, research suggests that human beings can perceive more than 200 FPS.

The point is that when it comes to PC gaming, more than 30 FPS is noticeable. In addition, the PC is an interactive device and the camera view often responds to user input from the mouse. The frame rate has to be quick enough to respond instantly to this user input. Otherwise, the user can feel the lag. This is especially noticeable in twitch games like first-person shooters that require precise aim.

Most PC monitors today cap out at 60 Hz, which means that the screen can refresh 60 times a second (there are a few 120 MHz monitors available for 3D use, but these are far from mainstream). Now, the question becomes: what if your PC is rendering more than 60 FPS? If your machine is fast enough to deliver 100 FPS to a 60 Hz monitor, what happens?

Unfortunately, more performance doesn't always equal better visuals. If your PC is sending out more frames than your monitor can display, what's likely going to happen is that the screen will refresh before the previous frame has finished drawing. This visual artifact is called tearing, and it's not pleasant. This is why vertical synchronization (v-sync) was developed.

Without going into details, v-sync limits your frame rate so that is doesn't exceed the monitor's, therefore eliminating tearing. When we benchmark games, we're usually looking for the performance cap, so we turn v-sync off, but for actual gameplay, you're probably better off enabling triple-buffered v-sync if your title supports the option.

Knowing all of this, we will conclude that a PC user with a 60 Hz monitor can certainly perceive up to 60 FPS. This is a widely accepted performance target for PC games, and now it's a little clearer why.

Finally, we need to consider how we measure game performance. Often, for a quick indicator, we record the average FPS. The problem is that average FPS is an aggregate number that doesn't tell us how low the frame rate can go. You can experience an average of 60 FPS that dips down to 10 FPS during demanding parts of the game, and 10 FPS is choppy by everyone's standards.

Because of this, you should pay attention to minimum FPS. Ideally, the minimum FPS value is 60, but a minimum FPS of 30 or even 20 can be acceptable if it happens for very short stints in demanding parts of a game.

Even the type of game you're playing can determine whether a certain minimum FPS is acceptable. In a first-person shooter, that lag might be enough to mess with your aim during a heated battle. But in a top-view, real-time strategy game, the drop in frame rate probably won't have much of an effect on your view or your click-and-drag inputs.

This is a lot of information to assimilate, but it is critical for the purposes of our review. Remember, we're trying to find out whether or not there is a point in purchasing a CPU that is more expensive than an Athlon II X3 440 for gaming purposes. Now, we know any frame rate advantage over 60 FPS is somewhat useless, but that any minimum frame rate advantage up to 60 FPS can be critical.

We wanted to keep the comparisons crystal clear, so we're going to make it simple. We're pitting AMD's Athlon II X3 440 against a Core i7-920. Yes, the Core i7-920 costs more than three times as much as the Athlon II X3 440, but remember that game performance will be bottlenecked to a large extent by the graphics subsystem.

As far as graphics cards go, we test two configurations: one with a single Radeon HD 5850 and the other with two Radeon HD 5870s in CrossFire. We test the games across 1280x1024, 1680x1050, 1920x1080, and 2560x1600 resolutions.

Because the Core i7-920 utilizes triple-channel memory, we use three 1GB sticks for a total of 3GB of RAM. The dual-channel AMD platform will use two 2GB sticks for a total of 4GB. From our experience, the single gigabyte of RAM difference should have no effect on gaming performance, but if we see any disparity, we will make note of memory usage. The RAM timings and speed are identical between both systems.

We're using the Gigabyte MA790XT-UD4P motherboard with an Athlon II X3 440 and the ASRock X58 SuperComputer with Intel's Core i7-920. Note that the 790X chipset on the Athlon board can't support full 16x PCI Express (PCIe) bandwidth for each graphics card. To keep things comparable, we put the second Radeon HD 5870 in a PCIe slot with 8x bandwidth when using CrossFire on the ASRock X58 board. 

AMD Test System
Intel Test System
CPU
AMD Athlon II X3 440 (Deneb)
3.0 GHz, FSB-200 MHz

Intel Core i7-920 (Nehalem)
2.67 GHz, QPI-4200, 8MB Shared L3 Cache
Motherboard

Gigabyte GA-MA790XT-UD4P
AMD790X, BIOS F7

ASRock X58 SuperComputer
Intel X58, BIOS P1.90
Networking
Onboard Gigabit LAN controller

Onboard Gigabit LAN controller
Memory

Mushkin PC3-10700
4GB Dual-Channel 2 x 2,048MB,
DDR3-1340, CL 9-9-9-24-1T

Kingston PC3-10700
3GB Triple-Channel 3 x 1,024MB,
DDR3-1066, CL 8-8-8-19-1T
Graphics

Sapphire Radeon HD 5850
725 MHz GPU, 1GB GDDR5 RAM at 1,000 MHz
Hard Drive

Western Digital Caviar WD50 00AAJS-00YFA
500GB, 7,200 RPM, 8MB cache, SATA 3.0 Gb/s
Power

Thermaltake Toughpower 1,200W
1,200W, ATX 12V 2.2, EPS 12v 2.91
Software and Drivers
Operating System
Microsoft Windows 7 64-bit
DirectX version DirectX 11
Graphics Drivers

ATI Catalyst 10.3
Benchmark Configuration

3D Games
Crysis

Patch 1.2.1, DirectX 10, 32-bit executable,
benchmark tool, High Settings, No AA, No AF
Far Cry 2

DirectX 10, in-game benchmark
Ultra-High Settings, No AA, No AF
S.T.A.L.K.E.R: Call of Pripyat

Ultra High Preset, DirectX 11, EFDL, no MSAA, Sunshafts Benchmark
World In Conflict: Soviet Assault

DirectX 10, timedemo
Very High Details, 4x AA/4x AF

There are some people who might get the impression that we're being unfairly hard on the Athlon II X3 440 by pitting it against the Core i7-920. In fact, the opposite is true. We have tremendous confidence in the gaming abilities of AMD's Athlon II X3 440, and that's why we think it's up to this kind of challenge.

It's all too easy to look at benchmark graphs and get caught up in the trends, but let me point something out to you: in every single game we benchmarked at 1920x1080, the Athlon II X3 440 was capable of a playable average frame rate in excess of 40 FPS. All of the games we tested were benchmarked at attractive and demanding visual settings, and all of them have a reputation for higher-end hardware requirements.

But to those suggesting that there is never a need for a better gaming CPU than the Athlon II X3 440, the facts show that this is simply not true. It is very clear that the Core i7-920 sports notable gaming advantages in a number of scenarios.

Breaking It Down

The first scenario is minimum frame rates. As we've discussed, minimum frame rates are far more important than average frame rates, and any advantage here is noticeable. When we tested World in Conflict, one of the more CPU-dependent games we've tested, it became apparent that the Athlon II X3 440 does not have the same capabilities as the Core i7-920. The Core i7-920 doubles the Athlon II X3 440's minimum of 10 FPS in this title. Granted, the Athlon II X3 440 also achieves a better minimum frame rate in S.T.A.L.K.E.R.: Call of Pripyat, but the Core i7-920 manages to double 10 FPS in that title, too. In general, the Athlon II X3 440 might not be the best choice for CPU-intensive games like World in Conflict and perhaps even CPU-intensive, real-time strategy games in general.

The second scenario in which the Athlon II X3 440 might not be ideal is when multiple graphics cards are employed. When we use two Radeon HD 5870 cards in CrossFire, the Core i7-920 system stretches its legs, while the Athlon II-based system doesn't seem to gain much additional performance at all. In fact, when we compare the Athlon II X3 440 results in CrossFire mode with the single-card Core i7-920 results, we are surprised to see that the Core i7-920 manages to beat the Athlon-based system more often than not (at least up to 1920x1080). At 2560x1600, the graphics subsystem is always the bottleneck. But realistically, who pairs an extremely expensive 30" monitor with one of the cheapest CPUs available?

To summarize, the Athlon II X3 440 is an excellent budget gaming processor for single graphics card applications, and probably represents the best price/performance value we've seen to date. But for folks with more cash who are looking for greater performance out of their gaming system (particularly when using multi-card graphics configurations or CPU-intensive game titles) ,higher-end CPUs are definitely a viable option. Remember that the name of the game here is balance. As you scale up graphics muscle, adding the processing horsepower to match will yield an optimal balance between the two subsystems. 

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