It is true that a dedicated graphics card will improve Photoshop performance; especially in Photoshop CS6 and Photoshop CC which take advantage of the Mercury Performance Engine that utilizes more GPU. But most people still don't know what specs they actually need for a Photoshop Graphics Card and why.
It’s a common misconception that Adobe Photoshop requires a high end graphics card for improved performance and functionality. It is true that a dedicated graphics card will improve Photoshop performance; especially in Photoshop CS6 and Photoshop CC which take advantage of the Mercury Performance Engine that utilizes more GPU. But most people still don’t know what specs they actually need for a Photoshop Graphics Card and why.
Photoshop uses Graphics Cards very differently than video games. So buying a Video Card that would perform well for gaming will usually work, its not the best way to get the most bang for your buck.
Buying a Video Graphics Card for Photoshop
When buying a Graphics Card for Photoshop many fall into the specs that are marketed toward gamers, such as VRAM and CUDA Cores/Streaming Cores. VRAM isn’t really important for Photoshop assuming you already have a decent amount of overall RAM (8GB or more). As for CUDA Cores/Streaming Cores, Photoshop’s primary GPU intensive features usuaully only use a maximum of 500 CUDA Cores when working with larger images such as those from DSLR Camera, but if you are going to be working large and complex images and photo manipulation a Video Card with at least 1000 CUDA Cores is ideal.
If you are also using Adobe After Effects more CUDA Cores would be better, however if you are only using Photoshop you don’t need to max out this feature. Memory Interface Width is actually more important to GPU Performance for Photoshop (if not in general). 4GB 128Bit Video Card is not as good as a 2GB 256Bit Video Card. If you consider your data a vehichles then 128Bit Video Cards are like having those cars on 4 lanes, where as a 256Bit Card would be like having them on 8 lanes.
Graphics Clock Speed would be the speed limit on those individual lanes of traffic. The other spec you need to pay attention to is Bandwidth.