X4 Ray Tracing - Optimal CPU

[Ian Pellant]

Hi Doug,

The "choice" is mostly between AMD or Intel....

New AMD FX8150 (8 core) seems good on paper.
Intel web selector recommends for CAD the i7-2600 with a separate video card (many Intel i series have varying inbuilt GPUs - but they are not specialised. DirectX rather than OpenGL targeted). The 2600 has minimal on chip GPU; then add a good OpenGL video card.

I found a web review of the FX8150 ("Bulldozer") which did a lot of single then multi-core benchmark comparisons with the i5-2500. Results generally indicated that the thread / core processing distribution was erratic with the AMD chip - Apparently Windows 7 doesn't know how to optimise for the new AMD chip. Some good results, some poor. Generally the Intel outperformed it until the task hit the sweet spot with the AMD, then it "Bulldozed" ahead.

CPU benchmarks have always been synthetic and not necessarily indicative of specific application performance.

What I do not know is: how the CA Ray Tracer will spectrum the load across threads and cores in the AMD vs Intel chip architectures. AMD claim 8 true cores vs Intel 4 core 2 threads per core. L1 and L2 caches may also be an issue. Large caches can slow down small fetches so a lot depends on the size and frequency of data calls. Ray Tracing will do a lot of data fetches? Will cache size and pipeline be significant factors??

An AMD system will probably be cheaper than an Intel. The computer will sit in the office working Chief Architect 90% of the time - so games, surround sound and Blu-ray movies are not required. Neither will it have several Microsoft Office apps open. AMD seem to be trying for the specialised users while Intel are after the mass market.

About 4 years ago, in a Revit users group we benchmarked several tasks (file opening, 3D view rotation, rendering, etc) and the humble AMD Sempron outperformed much more expensive Intel processors, against all expectations. The key seemed to be the small cache with an efficient data pipeline in the Sempron was quicker getting single, sequential tasks done than the Intel chips with dual cores and impressively large caches. With a 40 Mb Revit file, an 8Mb cache is a waste of time. Interesting.

Cheers.