Dual Processor Gaming

Dual CPUs systems were not originally intended for consumers. At a time when DOS or Windows 95 was what gamers needed, multiprocessor systems were only supported by Windows NT and Unix-like operating systems. Today things are different. The gaming OS of choice is Windows XP Professional, which also happens to support dual-CPUs natively.

CPU utilization while playing a high-defintion Windows Media 9 movie

By native support, this means that the system will take advantage of multiple processors whenever possible. In the best case, you have an “SMP aware” application that is designed to take advantage of both processors simultaneously. These applications can be difficult to program because the developer needs to make sure both CPUs are running efficiently so as not to take one step forward, and two steps back synchronizing the two processes.

At the moment, few games support SMP (symmetric multiprocessing), but if all goes according to plan, DOOM III will support SMP. Although HyperThreading was designed to keep the Pentium 4’s pipeline busy, it also has the potential to boost SMP development, as companies begin to consider programming with a multithreaded model. Companies such as Massive (Aquanox/Aquamark) are seeing gaming performance benefits from HyperThreading and it’s likely to be something we’ll see in the future. Dual processors are also supported by applications such as Adobe Photoshop/After Effects as well as other similarly high-end computationally intensive applications.

What’s in it for me?

A SMP-aware application is the best case scenario, but you still get an advantage to two CPUs with other applications. When you’re running a game, most of the CPU is spent processing the game data, however a small amount is used by Windows to manage your swap file, to check email in the background, to keep drivers and services running, etc. With a dual processor, Windows will intelligently distribute the workload between the CPUs. Your game will be able to take 100% advantage of the primary CPU while housekeeping applications can run on the second CPU. Another advantage would be multitasking –you can encode movies/audio, continue Folding @ Home, or batch process images while you play games. It’s probably not something you do all the time, but wouldn’t it be nice to be able to use your computer while you’re doing something computationally expensive?

Any application with more than one thread can take advantage of multiple CPUs; it is also possible to force an application onto one CPU

The coolest “luxury” feature of dual processors is that you’ll almost never need to wait for your PC again. Every once in a while, Internet Explorer will slow to a crawl as it loads a plug-in or encounters something unusual that eats up 100% CPU for a short while. While this is going on, your system becomes unresponsive and acts as if it’s dead. On a dual CPU system, this is often avoided because the second CPU is available. With two CPUs, your system always seems ready to respond to your commands.

The predicament

Knowing that, which system would you prefer: a dual Opteron, or a single P4 or Athlon 64? Depends on the applications you run right? Well, this system is supposed to be good for games and digital imaging and scientific computing. What’s the right CPU for work and play?

If you were to look at the existing set of reviews on the Internet for your answer, you wouldn’t be able to come to a satisfactory conclusion. There are sites reviewing Opterons with only PC2100 memory, and “workstations” powered by on-board ATI Rage XL graphics chips. Some sites test dual processors with only single-threaded applications, and then complain that the appropriate benchmark would cost many thousands of dollars and be too difficult to work with. Most annoying is when reviewers run benchmarks and make conclusions without really understanding what’s going on.

That’s the second reason for writing this article: we’re going to address some of the gaps in dual CPU benchmarking. What we want to know is if an Opteron remains “fast enough” for games, but offers additional speed with SMP-capable digital photography applications.