Intel HD 4000 and GT 650M

[Soccer5se]

Could someone explain how having these two graphic cards works? The intel is 512mb and the GT is 1GB does that mean it's like having a 1.5GB graphic card in my rMBP?

This is my second Mac and my first one only had onboard graphics so I am wondering how these graphics cards work together?

Thanks

Rich

 

[Auzburner]

They work separately, so the video memory does not add. The discrete card (650M) will automatically engage when you begin to perform more graphically intensive tasks (Gaming, High-res video, etc). Otherwise, the low power-consuming 4000 is what will typically power your display when web browsing or listening to iTunes and things of the like.

The 4000 is considered the integrated chip that is included with the motherboard/processor. The discrete card was separately selected by Apple to power the retina display when needed.

 

[simsaladimbamba]

The Intel is an Integrated Graphics Processor, meaning it is integrated into the CPU/chipset and shares its RAM (memory) with the main RAM you have, thus if you have 4 GB of RAM and the Intel takes 512 MB RAM, you only have 3.5 GB of RAM left for everything else.
The GT 650M is a dedicated GPU (dGPU), meaning it has its own chip with its own RAM, thus it does not take away 1 GB of RAM from your 4 GB of RAM.

Both GPUs run at different times, never at the same time, thus they cannot share the workload.
As mentioned before, the Intel is used in less graphic intensive task, the GT 650M is used when more graphic power is needed.

Also take a look at gfxCardStatus, a tool to show you which GPU is active and also a tool to select which GPU you want to have active.