New Computer

Hi I’m looking to buy a new computer,

Would the new Imac 5k with Upgraded Ram 16gb and Upgraded Gpu 4gb, or does it suck for blender usage ?

AMD Radeon R9 M295X graphics processor with 4GB of GDDR5 memory

I run blender on a macbook air with intel 4000 GPU. I can do a lot of cool things, and mostly render in realtime using cycles. The only thing that drags med down is final render time. I think you are pretty safe buying a mac 5k, however I think you can get away a lot cheaper if you want to.

Fast Cycles rendering = GPU rendering = CUDA compatible GPU = nVidia cards only.
That’s the status quo right now with Blender, unfortunately. Of course modeling/animating etc. will work just fine on that machine, but if it is raw render speed your after, AMD graphics solutions are not really recommendable with Blender - at this time.

Of course you can still render on the CPU, but even any mid-level nVidia GPU will run circles around your CPU when it comes to rendering.

Another thing to notice is that iMacs come with “notebook class” graphics cards (to fit into the slim chassis), which are invariably less performant than their desktop counterparts.