Does HiDPI (Retina) technology utilize GPU resources?

As I understand it should, but I can't find any explicit statement. This is important for me because I'm trying to understand which MacBook should I use - with external GPU or not. Still I can assume that the answer to the question is yes because Apple sells 15-inch with external GPU while 13-inch without it.

UPDATE: In discussion bellow I found that my original question was wrong (also the wrong term was used - external, I meant discrete). I believed that OS resolution is an absolute setting for all applications. Now I assume that some functions work with native resolution, so it's obvious why they work slower on higher resolution.

Example of scaling to native resolution: https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio

Solution 1:

Retina is just a marketing word for a high resolution monitor. The trick is then that instead of just allowing the user to use a lower resolution than the display is physically capable of, macOS lies to the application about its size so it thinks that it is e.g 800x600. All the system calls that then actually draw stuff like text and graphics then knows about the lie and can utilize the full resolution of the monitor.

All this require GPU support (and was introduced a long way back) to work well so that is not the criteria.

The external GPU is useful however if you for any reason need more strength than the internal GPU can provide. Games and intense visualization rendering are obvious choices. As they consume more power they usually are only enabled when actually needed falling back on the internal GPU for normal chores.

Unless you know already that you will run these kind of programs the internal GPU will do fine.

Solution 2:

You're asking about HiDPI/Retina but that's irrelevant: all macOS screen output goes via the GPU.

It makes no difference if that GPU is:

• integrated (on the logic board)
• discrete (an additional card plugged into the logic board)
• external (additional hardware plugged in via Thunderbolt cable)

So the answer to your question is Yes.

Instead, you might want to ask: what are your needs from the GPU?

If you want to run macOS at 4K@60Hz then you'll need the integrated GPU in a rMBP from 2014 (15") or 2015 (13") or newer.

If you need 5K, then you're looking at the integrated GPU in a rMBP from 2016 onwards.

If there's no rMBP with a GPU that fits your needs, then you can look at a rMBP that will work with an external GPU (eGPU) over Thunderbolt.

Some 15" rMBP have two GPUs — one integrated and one discrete — that can be switched between via software automatically or on demand.

Ref: https://support.apple.com/en-gb/HT206587

macOS does the scaling from display settings to monitor native resolution using the GPU, rather than the monitor doing the scaling using its hardware.

I know this because I use a 10+ year old Apple Cinema HD Display that does not have any scaling technology inside yet I can still choose one of a number of resolutions that are different to its native resolution.

Ref: https://discussions.apple.com/thread/1444180?answerId=6900979022#6900979022