For many other industries, having the maximum number of cores is ideal. However, for Photoshop, there is a diminishing amount of performance improvement per core above 6-cores. Going from 2-cores to 4-cores and from 4-cores to 6-cores, there is a scaleable improvement. However as we increase to 8-cores and to 12-cores, the improvement nearly flattens. Please see resource for Adobe Photoshop CC - CPU Cores Scalability: MacPerformanceGuide.
To reassure this hypothesis, we found another resource that has concluded the following (Puget Systems):
- Photoshop does not work well with multiple physical CPUs
- Most actions in Photoshop are either single threaded or lightly threaded.
- Multi-threaded actions hit a point of diminishing returns after around 6 CPU cores, and most completely stop improving after 8 CPU cores.
Our recommendation when choosing a CPU is to simply go with a model that has a high frequency. For the Mac Pro tower, the fastest CPUs for Photoshop use is the Quad-Core 3.33GHz and 6-core 3.46GHz. For the Mac Pro cylinder, the fastest speed frequencies are the Quad-Core 3.7GHz and 6-core 3.5GHz.