See my answer here: https://news.ycombinator.com/item?id=11112078
This "Metal predates Vulkan" argument is getting old already since it's historically incorrect.
> It was released, what, 4 months after aMD announced mantle? That's not enough time to develop and deploy an entirely new API, from my memory Vulkan was more a response to Metal, DX12 and Mantle.
You remember it wrong. Again, see the link above.
According to Wikipedia's Vulkan article [1], "The Khronos Group began a project to create a next generation graphics API in July 2014..."
Wikipedia's Metal article [2] links to the presentation from WWDC 2014 (the first week in June 2014) where Metal was introduced. Apple doesn't ever per-announce APIs-- at this time Metal was available for developers to use.
The Mantle article [3] says AMD developed Mantle "...starting in 2013" (the referenced Forbes article is from September 2013.) I'm doubting this was ample notice for Apple to have elected to write Metal, design it, and implement it nearly completely for June 2014. However, I'd concede it is certainly possible (Apple just doesn't seem that nimble to me.)
I'd be interested in reading anything more authoritative than a comment board on the impetus behind what seems to be an industry-wide decision to create these lower-level APIs.
1 - https://en.wikipedia.org/wiki/Vulkan_(API)#History
You wouldn't find official documentation on AMD dealing with Apple and MS, because it was private. But you can clearly deduce that both Apple and MS had access to Mantle when designing their APIs by comparing them. It's even possible that AMD did some of the work for them.
Also, AMD never hid their intention to make Mantle open. They voiced it early on. So Apple and MS both new that would happen when they started working on Metal and DX12. And that's exactly what happened when AMD gave Mantle to Khronos. Vulkan essentially is an iteration over Mantle. Same as DX12 and Metal are.
Even if you assume it all happened by pure chance, and the stunning resemblance of design is just because many different people had the same way of thought - it's not going to explain why MS and Apple couldn't back Vulkan once they figured out where things are moving.