Why not? Most Metal apps have to support both model anyway, every professional app needs to run on a Mac Pro with a discrete gpu at the moment,
True, but the Intel programming model is de-facto being phased out and Apple has been advising the devs to assume UMA on the newer machines. Not to mention that innovations in Metal have been limited to Apples own GPUs since last year.
The great thing about a unified programming model is that your software works on a wide range of hardware. The often overlooked but key benefit of Apple Silicon is hardware platform unification. One can for example develop an image editing engine using a Mac Pro and then ship the same code to an iOS app. The quality of the software will improve significantly in the coming years because of this.
I don't think there is anything preventing Apple from using discrete GPUs with their arm CPU in the future
Nothing on the technical level, sure, but they don’t have anything to gain by using discrete GPUs. On the other hand, using powerful integrated GPUs gives them a consistent programming model, unified capabilities as well as UMA.
If you instead refer to third-party GPUs, no chance. Why would they want to cripple their most powerful workstations? And why would they want to fragment their software ecosystem? Apple wants you to use the unique features of their GPUs, and third-party GPU support is an obstacle. I mean, would you code your video processing engine to take advantage of tile shaders and new simd shuffle+fill hardware if you know that half of your customers run AMD GPUs that simply doesn’t support these features? Most will probably just target the common ground (the AMD GPU), leaving the potential of Apples‘s GPU underused. This is especially deadly to Apple given the fact that they will probably always lack in bandwidth compared to third-party GPUs. They need the devs to take the jump to the new smarter programming models to succeed.
By the way, these considerations is why I don’t share the enthusiasm Linux folks have regarding Proton. Sure, it’s a short-term victory, but the likely price will be the very existence of native Linux games. Why bother using Vulkan and texting for Linux if you can just develop for DX12 and Windows and make the community sort out the edge cases? Long term it might even lead to problems for Vulkan…
Unless they can scale their GPU to beat the equivalent AMD and Nvidia top cards.
Of course they can. Apples GPU IP is around 2-3 times more power efficient than Nvidia or AMD, and that’s just G13. We have no idea what kind of surprises they have for us this year.