"It depends". I would say that we're currently best optimised for around four cores. Less than that and you're very likely to be CPU bound. More than that and you're unlikely to ever see full CPU utilisation, which isn't a problem but nor are you getting any major benefits.
Trainz offers a lot of different use-cases, so this isn't true for everything- if you start installing content in the background, or you have scripts which are performing a lot of database searches, or you've recently installed the content that you're using and the game is pre-caching, etc, then more cores can offer an advantage- but in general four is enough.
Very roughly speaking, we have the following major threads which can take nearly a core each:
* One thread for communicating with the GPU. The faster your GPU and motherboard, and the more complex the scene, the more CPU time this can take.
* One thread for gameplay, in-game ui, scripts, and train physics.
* One thread for particle effect updating (and for PhysX, if that's enabled).
* One thread for culling and LOD calculation.
We also have quite a number of small threads, which generally won't come close to taking up an entire CPU core, or which only do so for short periods in normal operation:
* Background loaders.
* Sound playback.
* Database operations (searches, installation, validation).
* Pre-caching.
* Mesh stitching.
If I were to buy a new Intel machine now, i'd probably be looking at an 8-10 core CPU with the highest boost clockspeed I can find at a reasonable price point. That allows room for things to grow in the future.
chris
