X-bit labs

Choosing the Best CPU for Doom III

Category: CPU

by Ilya Gavrichenkov

[ 08/24/2004 | 11:16 PM ]

Having tested the graphics cards in the new Doom III we thought it would also be interesting to measure the performance of the contemporary CPUs in this game. We used a preliminarily recorded demo as well as the actual gameplay. The results turned out very unexpected. Read more about it now!

Table of contents:

• What Does Doom 3 Need Your Processor for?
  
• Testbed and Methods
  
• Test 1: Standard Demo
  
• Test 2: Our Own CPU-Burn Demo
  
• Test 3: Real Game Test
  
• Test 4: Memory for Doom 3
  
• Conclusion
  

The new game from id Software made us all reexamine and revise our hardware. A really powerful computer is needed for you to enjoy fully the superb graphics of Doom 3. For example, the recommended system configuration for this game lists a 3GHz CPU (or with a rating of 3000+), at least 512MB of RAM and a graphics card no worse than NVIDIA GeForce 5900/ATI RADEON 9700.

It’s no surprise then that many devoted gamers have faced the problem of upgrade yet another time now. We have already published two reports about the speed and graphics quality as provided by modern graphics cards in this game. You can read them by the following links:

• Doom III: Performance and Image Quality in Different Gaming Modes
• Be Doomed: Performance Preview of the Doom III Game.

However, we have hitherto omitted the problem of the central processor in Doom 3. Of course, it is the graphics card that affects the speed of this game most of all, but still, Doom 3 is a CPU-dependent game as you can see from the test results of graphics cards in simple graphics modes.

So, in this review we will examine the influence of the CPU and of the amount of system memory on the speed of Doom 3.

What Does Doom 3 Need Your Processor for?

Before showing you the results of our tests, let’s first discuss the uses the developers of the game had put the CPU to. So, from the numerous interviews of John Carmack, id Software’s Technical Director, at various Internet sites it seems that skinning and shadows are the CPU’s main responsibility in Doom 3. That is, the CPU calculates the positions of the characters’ “skins” as they move between certain key points. This approach helps to animate the characters as well as render their facial expressions.

Evidently, the realization of dynamic shadows is thus better implemented using the CPU resources, too. That’s why Doom 3 requires an assiduous CPU to run smoothly, as besides skinning and shadow generation the CPU has to solve the traditional problems of any game like monsters’ AI, the physics of the game scene and tangent space transformations, necessary for a correct depiction of the game events on the screen.

It’s rather easy to determine which system component – the graphics card or the CPU – is the bottleneck as concerns running Doom 3. There’s the r_skipRenderContext variable among the game engine options. Set to 1, it changes all calls of OpenGL functions to calls of zero functions. In other words, it “disables” all the game graphics. Comparing the speed of a demo record with and without graphics we would understand what the system’s brake is in each particular case. But we are going talk about our benchmarking methods in the next section of this report.