The GPUs in iOS devices are not made by Apple or exclusive to their platform. They are PowerVR GPUs designed by Imagination Technologies (and fabricated by Samsung). Many Android devices feature the same GPU designs that Apple uses.
But you can't replace the GPU and Apple has full source code to the driver stack (and probably wrote most of it themselves instead of using the source from ImgTec).
The only place where this is likely true is for their Intel graphics drivers - Intel is probably the only graphics company on the planet that treats their graphics hardware as something less than the most cherished of all trade secrets.
No, you can bet damned good money they get a "manual" and a binary blob from their GPU vendor and they have to do the same reverse engineering as the Mesa folk do, only they have the added advantage of not needing to recontribute any of their changes publicly.
I doubt OS X contains much if any code that Apple doesn't have the source to. This isn't so much speculation as common sense.
Apple as a company is the very embodiment of control. Ever since Jobs took the reigns back they have held the entire production pipeline of their products in an iron grip. I wouldn't imagine software, especially driver code that has such a massive impact on user experience to be any different.
GPU vendors allow game engine developers of a reasonable size access to the source of their drivers, why do you think that a company much more powerful (and actually a customer) would be denied the same access?
The implication they probably (re)wrote most if it themselves wouldn't surprise me much either. They have already shown that low level engineering is neither beneath them or beyond their capability. They produced their own ARM chips well ahead of the other vendors (even beating out veterans in that space like Qualcomm) and have continued to show they want to control everything except maybe the fab.
So lets be honest, the only thing that is likely to be true is they have access to everything and probably influence development of PowerVR hardware significantly.
> The only place where this is likely true is for their Intel graphics drivers
false. i cannot cite a source for this, but i know they have direct access to current nvidia and AMD driver source trees, which they themselves extend/modify.
