We had to chance to make a massive e-mail interview with Doug Binks, R&D Development Manager Crytek, and Leigh Davies, Intel, regarding Crysis, probably the hottest game in town for 2007.
PCGH: As far as performance is concerned, how will the engine scale with additional cores?
Doug Binks, R&D Development Manager Crytek: The performance scales well with additional cores, though the exact scaling will depend on the system settings and the capabilities of the rest of the PC. The higher quality physics and particle effects put large demands on the CPU, and as these are individually threaded good benefits can be seen with dual and quad core systems.
PCGH: What different calculations can be or are split up into different threads and what is the expected performance gain resulting from two respectively four or more cores?
Doug Binks, R&D Development Manager Crytek: The game code is heavily threaded, the most significant areas that are threaded are the primary game thread where the AI and most of the graphic is calculated, the physics, particles, audio, the graphic driver, some background data loading and decompression.
PCGH: What was the most disturbing problem when optimizing for 4 cores?
Doug Binks, R&D Development Manager Crytek: The two biggest problems we encountered were to do with synchronization and handling the asynchronous physics response in animation, movement and vehicle code.
PCGH: What about Triple Core Processors? Do they fit in the gap between dual and quadcore processors or are there any restrictions?
Leigh Davies, Intel: From a purely theoretical viewpoint this might be a good approach, but its likely that the price performance ratio would not be as good as for quad core.
PCGH: With a Core 2 Quad, there are 2 independent unified L2-Caches with 4 megs each. Did you encounter any performance restrictions due to coherency and synchronisation issues? Or the other way round: Could we expect performance increases (in theory) when using one large, unified L2-Cache instead of 2 (relatively) small and independent ones?
Doug Binks, R&D Development Manager Crytek: Cache coherency is always an issue, particularly with the large amounts of data were throwing around in Crysis. So wed always prefer more cache. Ideally the cores will be working on different data sets, so two separate caches works well.
PCGH: After playing the first levels, we get the impression, that Crysis is highly video card (mainly shader) limited and cpu performance doesnt matter much. What is your experience?
Doug Binks, R&D Development Manager Crytek: With a well balanced system the automatic quality settings should put the CPU and GPU in balance. Increasing the visual quality settings for physics and particles will lead to a more CPU bound experience, and increasing visual quality will lead to a more GPU bound experience.
PCGH: Are you working on a 64 bit version of the game? If yes, in what way will the additional 32 bit improve the game?
Doug Binks, R&D Development Manager Crytek: There is a 64-bit version of the game and Sandbox 2 level editor. The main benefit for the game is that with the expanded virtual address space available Crysis is able to load the entire level texture memory into memory (using both video and main memory), which gives both higher quality and a performance improvement. The level editor really requires being run in 64bit to be able to edit the larger levels, and we use 64bit systems throughout our development.
PCGH: If yes, is there also a 64-Bit-Version for Windows XP?
Doug Binks, R&D Development Manager Crytek: Yes.
PCGH: Could you please give us a few examples of new or enhanced engine features, that could be realized using 64 bit technology?
Doug Binks, R&D Development Manager Crytek: The main benefit here is the larger address space available. We are rapidly approaching a point where youll need a 64bit OS to play the highest quality games.
A second part of the Q&A with engine and physics related questions is also available.
Pictures: Doug Binks on the left, Leigh Davies on the right