PCGH: How important will main memory be for the overall performance? How much memory would you recommend?

Tim Sweeney: We require at least 512MB, and you'll want at least 2 gigabytes for optimal performance and detail. Unreal Engine 3 is very scalable in terms of memory usage, so it runs well on low-memory machines at the low texture-detail setting.

PCGH: It is well known that your engine supports multi core CPUs. What is the maximum number of threads the engine can calculate? What is the performance gain when you play UT 3 with a quad core CPU? Will the engine even support future CPU with more than four cores?

Tim Sweeney: Unreal Engine 3's threading support is quite scalable. We run a primary thread for gameplay, and a secondary thread for rendering. On machines with more than two cores, we run additional threads to accelerate various computing tasks, including physics and data decompression. There are clear performance benefits to quad-core, and though we haven't looked beyond that yet, I expect further gains beyond quad-core in future games within the lifetime of Unreal Engine 3.

PCGH: Are there any things you learned while developing Gears of War for next gen consoles that you can now benefit from when finalizing UT 3 for the PC?

Tim Sweeney: The Gears of War experience on Xbox 360 taught us to optimize for multi-core, and to improve the low-level performance of the key engine systems. This has carried over very well to PC. The division of UE3's rendering and gameplay into separate threads, implemented originally for 360, has brought even more significant gains on PC where there is a more heavyweight hardware abstraction layer in DirectX, hence more CPU time spent in rendering relative to gameplay.

Also, the 360 work we did resulted in an engine that also runs well on low-end and mid-range PCs. This is very important for games today; the high-end PC gaming market alone is not big enough to support next-generation games with budgets in the $10-20M range. You need to run on ordinary mass-market PCs as well. In reading PC gaming websites, one might get the impression that everyone owns a dual-core PC with a pair of $600 GPUs in SLI configuration, but the reality is very different. More than 80% of PCs sold today are still single-core, and have very low-end DirectX9 graphics capabilities. Unreal Engine 3 supports those configurations well.